A. Correct. Flagella are organelles defined by function rather than structure. Flagella vary greatly. Both prokaryotic and eukaryotic flagella can be used for swimming
B. Incorrect. prokaryotic and eukaryotic flagella differ greatly in protein composition, especially in the monomers.
C. Incorrect. Propulsion means to push forward or drive an object forward.
D. Incorrect. prokaryotic and eukaryotic flagella differ in structure because of the proteins and other polymers that made them.
E. Incorrect. The difference of protein composition causes also the difference in the chemical composition.

Description:

A flagellum is a lash-like appendage that protrudes from the cell body of certain bacterial and eukaryotic cells and whose primary function is locomotion, but it also often has a function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell. The similar structure in the archaea functions in the same way but is structurally different and has been termed the archaellum.


Flagella are organelles defined by function rather than structure. Flagella vary greatly. Both prokaryotic and eukaryotic flagella can be used for swimming but they differ greatly in protein composition, structure, and mechanism of propulsion. The word flagellum in Latin means whip.

An example of a flagellated bacterium is the ulcer-causing Helicobacter pylori, which uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium. An example of a eukaryotic flagellate cell is the mammalian sperm cell, which uses its flagellum to propel itself through the female reproductive tract. Eukaryotic flagella are structurally identical to eukaryotic cilia, although distinctions are sometimes made according to function or length. Fimbriae and pili are also thin appendages, but have diffThree types of flagella have so far been distinguished: bacterial, archaeal, and eukaryotic.

Prokaryotic flagella run in a rotary movement, while eukaryotic flagella run in a bending movement. The prokaryotic flagella use a rotary motor, and the eukaryotic flagella use a complex sliding filament system. Eukaryotic flagella are ATP driven, while prokaryote ones are proton-driven.
Three types of flagella have so far been distinguished: bacterial, archaeal, and eukaryotic.

The main differences between these three types are:

Bacterial flagella are helical filaments, each with a rotary motor at its base which can turn clockwise or counterclockwise. They provide two of several kinds of bacterial motility.
Archaeal flagella (archaella) are superficially similar to bacterial flagella, but are different in many details and considered non-homologous.
Eukaryotic flagella—those of animal, plant, and protist cells—are complex cellular projections that lash back and forth. Eukaryotic flagella are classed along with eukaryotic motile cilia as undulipodia to emphasize their distinctive wavy appendage role in cellular function or motility. Primary cilia are immotile, and are not undulipodia; they have a structurally different 9+0 axoneme rather than the 9+2 axoneme found in both flagella and motile cilia undulipodia.

A. Incorrect. Intracrine refers to a hormone that acts inside a cell, regulating intracellular events. In simple terms, it means that the cell stimulates itself by cellular production of a factor that acts within the cell.
B. Incorrect. Autocrine signals are produced by the target cell, are secreted, and affect the target cell itself via receptors. Sometimes autocrine cells can target cells close by if they are the same type of cell as the emitting cell. An example of this is immune cells.
C. Incorrect. Autocrine signals are produced by the target cell, are secreted, and affect the target cell itself via receptors. Sometimes autocrine cells can target cells close by if they are the same type of cell as the emitting cell. An example of this is immune cells.
D. Incorrect. Paracrine signaling is a form of cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behavior of those cells
E. Correct. Endocrine signals target distant cells. Endocrine cells produce hormones that travel through the blood to reach all parts of the body.

Description:

Cells communicate with each other via direct contact (juxtacrine signaling), over short distances (paracrine signaling), or over large distances and/or scales (endocrine signaling).

Some cell-cell communication requires direct cell-cell contact. Some cells can form gap junctions that connect their cytoplasm to the cytoplasm of adjacent cells. In cardiac muscle, gap junctions between adjacent cells allow for action potential propagation from the cardiac pacemaker region of the heart to spread and coordinately cause contraction of the heart.

The notch signaling mechanism is an example of juxtacrine signaling (also known as contact-dependent signaling) in which two adjacent cells must make physical contact in order to communicate. This requirement for direct contact allows for very precise control of cell differentiation during embryonic development. In the worm Caenorhabditis elegans, two cells of the developing gonad each have an equal chance of terminally differentiating or becoming a uterine precursor cell that continues to divide. The choice of which cell continues to divide is controlled by competition of cell surface signals. One cell will happen to produce more of a cell surface protein that activates the Notch receptor on the adjacent cell. This activates a feedback loop or system that reduces Notch expression in the cell that will differentiate and that increases Notch on the surface of the cell that continues as a stem cell.

Many cell signals are carried by molecules that are released by one cell and move to make contact with another cell. Endocrine signals are called hormones. Hormones are produced by endocrine cells and they travel through the blood to reach all parts of the body. The specificity of signaling can be controlled if only some cells can respond to a particular hormone. Paracrine signals such as retinoic acid target only cell in the vicinity of the emitting cell. Neurotransmitters represent another example of a paracrine signal. Some signaling molecules can function as both a hormone and a neurotransmitter. For example, epinephrine and norepinephrine can function as hormones when released from the adrenal gland and are transported to the heart by way of the bloodstream. Norepinephrine can also be produced by neurons to function as a neurotransmitter within the brain. Estrogen can be released by the ovary and function as a hormone or act locally via paracrine or autocrine signaling. Active species of oxygen and nitric oxide can also act as cellular messengers. This process is dubbed redox signaling.

The endocrine system is a chemical messenger system consisting of hormones, the group of glands of an organism that secrete those hormones directly into the circulatory system to regulate the function of distant target organs, and the feedback loops which modulate hormone release so that homeostasis is maintained. In humans, the major endocrine glands are the thyroid gland and the adrenal glands. Invertebrates, the hypothalamus is the neural control center for all endocrine systems. The study of the endocrine system and its disorders is known as endocrinology. Endocrinology is a branch of internal medicine.

Main glands of the endocrine system. Note that the thymus is no longer considered part of the endocrine system, as it does not produce hormones.

A. Incorrect. Phospholipids are a class of lipids that are a major component of all cell membranes
B. Incorrect.in the cell walls usually can find proteins.
C. Incorrect. histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes.
D. Incorrect. in the cell walls usually can’t find triglycerides
E. Correct. The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cytoplasmic membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts.

Description:

Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. Peptidoglycan is also involved in binary fission during bacterial cell reproduction.

The peptidoglycan layer is substantially thicker in Gram-positive bacteria (20 to 80 nanometers) than in Gram-negative bacteria (7 to 8 nanometers). Peptidoglycan forms around 90% of the dry weight of Gram-positive bacteria but only 10% of Gram-negative strains. Thus, the presence of high levels of peptidoglycan is the primary determinant of the characterization of bacteria as Gram-positive. In Gram-positive strains, it is important in attachment roles and serotyping purposes. For both Gram-positive and Gram-negative bacteria, particles of approximately 2 nm can pass through the peptidoglycan.

The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cytoplasmic membrane.

Description:

The cell envelope is composed of the plasma membrane and cell wall. As in other organisms, the bacterial cell wall provides structural integrity to the cell. In prokaryotes, the primary function of the cell wall is to protect the cell from internal turgor pressure caused by the much higher concentrations of proteins and other molecules inside the cell compared to its external environment. The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cytoplasmic membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape. It is relatively porous and is not considered to be a permeability barrier for small substrates. While all bacterial cell walls (with a few exceptions e.g. extracellular parasites such as Mycoplasma) contain peptidoglycan, not all cell walls have the same overall structures. Since the cell wall is required for bacterial survival but is absent in some eukaryotes, several antibiotics (notably the penicillins and cephalosporins) stop bacterial infections by interfering with cell wall synthesis, while having no effects on human cells which have no cell wall, only a cell membrane. There are two main types of bacterial cell walls, those of gram-positive bacteria and those of gram-negative bacteria, which are differentiated by their Gram staining characteristics. For both these types of bacteria, particles of approximately 2 nm can pass through the peptidoglycan. If the bacterial cell wall is entirely removed, it is called a protoplast while if it’s partially removed, it is called a spheroplast. β-Lactam antibiotics such as penicillin inhibit the formation of peptidoglycan cross-links in the bacterial cell wall. The enzyme lysozyme, found in human tears, also digests the cell wall of bacteria and is the body’s main defense against eye infections.

Gram-positive cell walls are thick and the peptidoglycan ( also known as murein) layer constitutes almost 95% of the cell wall in some gram-positive bacteria and as little as 5-10% of the cell wall in gram-negative bacteria. The gram-positive bacteria take up the crystal violet dye and are stained purple. The cell wall of some gram-positive bacteria can be completely dissolved by lysozymes which attacks the bonds between N-acetylmuramic acid and N-acetylglucosamine. In other gram-positive bacteria, such as Staphylococcus aureus, the walls are resistant to the action of lysozymes. They have O-acetyl groups on carbon-6 of some muramic acid residues. The matrix substances in the walls of gram-positive bacteria may be polysaccharides or teichoic acids. The latter is very widespread, but have been found only in gram-positive bacteria. There are two main types of teichoic acid: ribitol teichoic acids and glycerol teichoic acids. The latter is more widespread. These acids are polymers of ribitol phosphate and glycerol phosphate, respectively, and only located on the surface of many gram-positive bacteria. However, the exact function of teichoic acid is debated and not fully understood. A major component of the gram-positive cell wall is lipoteichoic acid. One of its purposes is providing an antigenic function. The lipid element is to be found in the membrane where its adhesive properties assist in its anchoring to the membrane.

Gram-negative cell walls are thin and unlike the gram-positive cell walls, they contain a thin peptidoglycan layer adjacent to the cytoplasmic membrane. Gram-negative bacteria are stained as pink color. The chemical structure of the outer membrane’s lipopolysaccharide is often unique to specific bacterial sub-species and is responsible for many of the antigenic properties of these strains.

The plasma membrane of the bacterial cytoplasmic membrane is composed of a phospholipid bilayer and thus has all of the general functions of a cell membrane such as acting as a permeability barrier for most molecules and serving as the location for the transport of molecules into the cell. In addition to these functions, prokaryotic membranes also function in energy conservation as the location about which a proton motive force is generated. Unlike eukaryotes, bacterial membranes (with some exceptions e.g. Mycoplasma and methanotrophs) generally do not contain sterols. However, many microbes do contain structurally related compounds called hopanoids which likely fulfill the same function. Unlike eukaryotes, bacteria can have a wide variety of fatty acids within their membranes. Along with typical saturated and unsaturated fatty acids, bacteria can contain fatty acids with additional methyl, hydroxy or even cyclic groups. The relative proportions of these fatty acids can be modulated by the bacterium to maintain the optimum fluidity of the membrane (e.g. following temperature change).
As a phospholipid bilayer, the lipid portion of the outer membrane is impermeable to charged molecules. However, channels called porins are present in the outer membrane that allows for passive transport of many ions, sugars and amino acids across the outer membrane. These molecules are therefore present in the periplasm, the region between the cytoplasmic and outer membranes. The periplasm contains the peptidoglycan layer and many proteins responsible for substrate binding or hydrolysis and reception of extracellular signals. The periplasm is thought to exist in a gel-like state rather than a liquid due to the high concentration of proteins and peptidoglycan found within it. Because of its location between the cytoplasmic and outer membranes, signals received and substrates bound are available to be transported across the cytoplasmic membrane using transport and signaling proteins embedded there.

• Totipotent:

Totipotent (omnipotent) stem cells can give rise to any of the 220 cell types found in an embryo as well as extra-embryonic cells (placenta).

• Pluripotent:

Pluripotent stem cells can give rise to all cell types of the body (but not the placenta).

• Multipotent:

Multipotent stem cells can develop into a limited number of cell types in a particular lineage.

• Progenitor cells

A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its “target” cell.

• Erythroid:

Erythroid cells are differentiated from hematopoietic stem cells (HSCs) that reside within specific niches in the adult bone marrow. Therefore they are considered as differentiated cells, then they have the lowest potency.

A plasmid is a small DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms (the answer is B).

Description:

In nature, plasmids often carry genes that may benefit the survival of the organism, for example, antibiotic resistance. While the chromosomes are big and contain all the essential genetic information for living under normal conditions, plasmids usually are very small and contain only additional genes that may be useful to the organism under certain situations or particular conditions. Artificial plasmids are widely used as vectors in molecular cloning, serving to drive the replication of recombinant DNA sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via transformation.

Plasmids are considered replicons, units of DNA capable of replicating autonomously within a suitable host. However, plasmids, like viruses, are not generally classified as life. Plasmids are transmitted from one bacterium to another (even of another species) mostly through conjugation. This host-to-host transfer of genetic material is one mechanism of horizontal gene transfer, and plasmids are considered part of the mobilome. Unlike viruses (which encase their genetic material in a protective protein coat called a capsid), plasmids are “naked” DNA and do not encode genes necessary to encase the genetic material for transfer to a new host. However, some classes of plasmids encode the conjugative “sex” pilus necessary for their own transfer. The size of the plasmid varies from 1 to over 200 kbp, and the number of identical plasmids in a single cell can range anywhere from one to thousands under some circumstances.

The relationship between microbes and plasmid DNA is neither parasitic nor mutualistic because each implies the presence of an independent species living in a detrimental or commensal state with the host organism. Rather, plasmids provide a mechanism for horizontal gene transfer within a population of microbes and typically provide a selective advantage under a given environmental state. Plasmids may carry genes that provide resistance to naturally occurring antibiotics in a competitive environmental niche, or the proteins produced may act as toxins under similar circumstances, or allow the organism to utilize particular organic compounds that would be advantageous when nutrients are scarce.

There are two types of plasmid integration into a host bacteria: non-integrating plasmids replicate as with the top instance, whereas episomes, the lower example, can integrate into the host chromosome.

A. Correct. Chemoautotrophs use inorganic energy sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia
B. Incorrect. Chemoautotrophs use inorganic energy sources such as elemental sulfur, not molecular sulfur
C. Incorrect. Chemoautotrophs don’t use inorganic energy sources such as Mg.
D. Incorrect. Chemoautotrophs use inorganic energy sources such as molecular hydrogen, not elemental hydrogen
E. Incorrect. Chemoautotrophs use inorganic energy sources such as hydrogen sulfide, not oxygen sulfide

Description:

Chemoautotrophs in addition to deriving energy from chemical reactions, synthesize all necessary organic compounds from carbon dioxide. Chemoautotrophs use inorganic energy sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia. Most chemoautotrophs are extremophiles, bacteria or archaea that live in hostile environments (such as deep-sea vents) and are the primary producers in such ecosystems. Chemoautotrophs generally fall into several groups: methanogens, halophiles, sulfur oxidizers and reducers, nitrifiers, anammox bacteria, and thermoacidophiles. An example of one of these prokaryotes would be Sulfolobus. Chemolithotrophic growth can be dramatically fast, such as Hydrogenovibrio crunogenus with a doubling time of around one hour.

The term “chemosynthesis”, coined in 1897 by Wilhelm Pfeffer, originally was defined as the energy production by oxidation of inorganic substances in association with autotrophy – what would be named today as chemolithoautotrophy. Later, the term would include also the chemoorganoautotrophy, that is, it can be seen as a synonym of chemoautotrophy.

Chemoheterotroph

Chemoheterotrophs (or chemotrophic heterotrophs) (Gr: Chemo (χημία) = chemical, hetero (ἕτερος) = (an)other, troph (τροφιά) = nourishment) are unable to fix carbon to form their own organic compounds. Chemoheterotrophs can be chemolithoheterotrophs, utilizing inorganic energy sources such as sulfur or chemoorganoheterotrophs, utilizing organic energy sources such as carbohydrates, lipids, and proteins. Most animals and fungi are examples of chemoheterotrophs.

Iron- and manganese-oxidizing bacteria

In the deep oceans, iron-oxidizing bacteria derive their energy needs by oxidizing ferrous iron (Fe2+) to ferric iron (Fe3+). The electron conserved from this reaction reduces the respiratory chain and can be thus used in the synthesis of ATP by forwarding electron transport or NADH by reverse electron transport, replacing or augmenting traditional phototrophism.

The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, providing energy to power ATP synthase.

In general, iron-oxidizing bacteria can exist only in areas with high ferrous iron concentrations, such as new lava beds or areas of hydrothermal activity. Most of the ocean is devoid of ferrous iron, due to both the oxidative effect of dissolved oxygen in the water and the tendency of bacteria to take up the iron.
Lava beds supply bacteria with ferrous iron straight from the Earth’s mantle, but only newly formed igneous rocks have high enough levels of ferrous iron. In addition, because oxygen is necessary for the reaction, these bacteria are much more common in the upper ocean, where oxygen is more abundant.
What is still unknown is how exactly iron bacteria extract iron from rock. It is accepted that some mechanism exists that eats away at the rock, perhaps through specialized enzymes or compounds that bring more FeO to the surface. It has been long debated about how much of the weathering of the rock is due to biotic components and how much can be attributed to abiotic components.
Hydrothermal vents also release large quantities of dissolved iron into the deep ocean, allowing bacteria to survive. In addition, the high thermal gradient around vent systems means a wide variety of bacteria can coexist, each with its own specialized temperature niche.
Regardless of the catalytic method used, chemoautotrophic bacteria provide a significant but frequently overlooked food source for deep-sea ecosystems – which otherwise receive limited sunlight and organic nutrients.
Manganese-oxidizing bacteria also make use of igneous lava rocks in much the same way; by oxidizing manganous manganese (Mn2+) into manganic (Mn4+) manganese. Manganese is more scarce than iron oceanic crust but it is much easier for bacteria to extract from an igneous glass. In addition, each manganese oxidation donates two electrons to the cell versus one for each iron oxidation, though the amount of ATP or NADH that can be synthesized in couple to these reactions varies with pH and specific reaction thermodynamics in terms of how much of a Gibbs free energy change there is during the oxidation reactions versus the energy change required for the formation of ATP or NADH, all of which vary with concentration, pH, etc. Much still remains unknown about manganese-oxidizing bacteria because they have not been cultured and documented to any great extent.

A. Incorrect. conversion of the malate to the oxaloacetate needs NAD+
B. Correct. water! is a kind of oxide hydrogen
C. Incorrect. The overall yield of energy-containing compounds from the TCA cycle is three NADH, one FADH2, and one GTP.
D. Incorrect. Hydrogen peroxide is a chemical compound with the formula H202
E. Incorrect. a precursor is a compound that participates in a chemical reaction that produces another compound

Description:

Krebs cycle is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins, into adenosine triphosphate (ATP) and carbon dioxide. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically. Even though it is branded as a ‘cycle’, it is not necessary for metabolites to follow only one specific route; at least three segments of the citric acid cycle have been recognized.

The name of this metabolic pathway is derived from the citric acid (a type of tricarboxylic acid, often called citrate, as the ionized form predominates at biological pH) that is consumed and then regenerated by this sequence of reactions to complete the cycle. The cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, and produces carbon dioxide as a waste byproduct. The NADH generated by the citric acid cycle is fed into the oxidative phosphorylation (electron transport) pathway. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable chemical energy in the form of ATP.

In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. In prokaryotic cells, such as bacteria, which lack mitochondria, the citric acid cycle reaction sequence is performed in the cytosol with the proton gradient for ATP production being across the cell’s surface (plasma membrane) rather than the inner membrane of the mitochondrion. The overall yield of energy-containing compounds from the TCA cycle is three NADH, one FADH2, and one GTP.

The activated lymphocytes can enlarge to 30 µm in diameter in lymphoid tissues. They have an intensely basophilic cytoplasm, due to their increased protein synthesis. The cytoplasmic organelles of the B lymphocytes are characteristic of eukaryotic cells. Some organelles, such as the Golgi zone, are poorly developed but he cytoplasm contains free ribosomes, occasional ribosome clusters, and strands of the rough endoplasmic reticulum (ER). the sum of Golgi and ER is called as Microsome. Therefore the correct answer is Microsome.

A. Incorrect. In the citric acid cycle, all the intermediates (e.g. citrate, iso-citrate, alpha-ketoglutarate, succinate, fumarate, malate, and oxaloacetate) are regenerated during each turn of the cycle. Adding more of any of these intermediates to the mitochondrion, therefore, means that that additional amount is retained within the cycle, increasing all the other intermediates as one is converted into the other
B. Incorrect. the addition of any one of them to the cycle has an anaplerotic effect, and its removal has a cataplerotic effect. These anaplerotic and cataplerotic reactions will, during the course of the cycle, increase or decrease the amount of oxaloacetate available to combine with acetyl-CoA to form citric acid.
C. Incorrect. Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle
D. Incorrect. Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle
E. Correct. it is possible for pyruvate to be carboxylated by pyruvate carboxylase to form oxaloacetate. This latter reaction “fills up” the amount of oxaloacetate in the citric acid cycle, and is, therefore, an anaplerotic reaction, increasing the cycle’s capacity to metabolize acetyl-CoA when the tissue’s energy needs are suddenly increased by activity.

Description:

Major metabolic pathways converging on the citric acid cycle

Several catabolic pathways converge on the citric acid cycle. Most of these reactions add intermediates to the citric acid cycle, and are therefore known as anaplerotic reactions, from the Greek meaning to “fill up”. These increase the amount of acetyl CoA that the cycle is able to carry, increasing the mitochondrion’s capability to carry out respiration if this is otherwise a limiting factor. Processes that remove intermediates from the cycle are termed “cataplerotic” reactions.

In this section and in the next, the citric acid cycle intermediates are indicated in italics to distinguish them from other substrates and end-products.

Pyruvate molecules produced by glycolysis are actively transported across the inner mitochondrial membrane, and into the matrix. Here they can be oxidized and combined with coenzyme A to form CO2, acetyl-CoA, and NADH, as in the normal cycle.

However, it is also possible for pyruvate to be carboxylated by pyruvate carboxylase to form oxaloacetate. This latter reaction “fills up” the amount of oxaloacetate in the citric acid cycle, and is, therefore, an anaplerotic reaction, increasing the cycle’s capacity to metabolize acetyl-CoA when the tissue’s energy needs (e.g. in muscle) are suddenly increased by activity.

In the citric acid cycle, all the intermediates (e.g. citrate, iso-citrate, alpha-ketoglutarate, succinate, fumarate, malate, and oxaloacetate) are regenerated during each turn of the cycle. Adding more of any of these intermediates to the mitochondrion, therefore, means that that additional amount is retained within the cycle, increasing all the other intermediates as one is converted into the other. Hence the addition of any one of them to the cycle has an anaplerotic effect, and its removal has a cataplerotic effect. These anaplerotic and cataplerotic reactions will, during the course of the cycle, increase or decrease the amount of oxaloacetate available to combine with acetyl-CoA to form citric acid. This in turn increases or decreases the rate of ATP production by the mitochondrion, and thus the availability of ATP to the cell.

Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle. With each turn of the cycle, one molecule of acetyl-CoA is consumed for every molecule of oxaloacetate present in the mitochondrial matrix and is never regenerated. It is the oxidation of the acetate portion of acetyl-CoA that produces CO2 and water, with the energy thus released captured in the form of ATP. The three steps of beta-oxidation resemble the steps that occur in the production of oxaloacetate from succinate in the TCA cycle. Acyl-CoA is oxidized to trans-Enoyl-CoA while FAD is reduced to FADH2, which is similar to the oxidation of succinate to fumarate. Following, trans-Enoyl-CoA is hydrated across the double bond to beta-hydroxyacyl-CoA, just like fumarate is hydrated to malate. Lastly, beta-hydroxyacyl-CoA is oxidized to beta-ketoacyl-CoA while NAD+ is reduced to NADH, which follows the same process as the oxidation of malate to oxaloacetate.

In the liver, the carboxylation of cytosolic pyruvate into intra-mitochondrial oxaloacetate is an early step in the gluconeogenic pathway which converts lactate and de-aminated alanine into glucose, under the influence of high levels of glucagon and/or epinephrine in the blood. Here the addition of oxaloacetate to the mitochondrion does not have a net anaplerotic effect, as another citric acid cycle intermediate (malate) is immediately removed from the mitochondrion to be converted into cytosolic oxaloacetate, which is ultimately converted into glucose, in a process that is almost the reverse of glycolysis.

In protein catabolism, proteins are broken down by proteases into their constituent amino acids. Their carbon skeletons (i.e. the de-aminated amino acids) may either enter the citric acid cycle as intermediates (e.g. alpha-ketoglutarate derived from glutamate or glutamine), having an anaplerotic effect on the cycle, or, in the case of leucine, isoleucine, lysine, phenylalanine, tryptophan, and tyrosine, they are converted into acetyl-CoA which can be burned to CO2 and water, or used to form ketone bodies, which too can only be burned in tissues other than the liver where they are formed, or excreted via the urine or breath. These latter amino acids are therefore termed “ketogenic” amino acids, whereas those that enter the citric acid cycle as intermediates can only be cataplerotically removed by entering the gluconeogenic pathway via malate which is transported out of the mitochondrion to be converted into cytosolic oxaloacetate and ultimately into glucose. These are the so-called “glucogenic” amino acids. De-aminated alanine, cysteine, glycine, serine, and threonine are converted to pyruvate and can consequently either enter the citric acid cycle as oxaloacetate (an anaplerotic reaction) or as acetyl-CoA to be disposed of as CO2 and water.

In fat catabolism, triglycerides are hydrolyzed to break them into fatty acids and glycerol. In the liver, the glycerol can be converted into glucose via dihydroxyacetone phosphate and glyceraldehyde-3-phosphate by way of gluconeogenesis. In many tissues, especially the heart and skeletal muscle tissue, fatty acids are broken down through a process known as beta-oxidation, which results in the production of mitochondrial acetyl-CoA, which can be used in the citric acid cycle. Beta oxidation of fatty acids with an odd number of methylene bridges produces propionyl-CoA, which is then converted into succinyl-CoA and fed into the citric acid cycle as an anaplerotic intermediate

The total energy gained from the complete breakdown of one (six-carbon) molecule of glucose by glycolysis, the formation of 2 acetyl-CoA molecules, their catabolism in the citric acid cycle, and oxidative phosphorylation equals about 30 ATP molecules, in eukaryotes. The number of ATP molecules derived from the beta-oxidation of a 6 carbon segment of a fatty acid chain and the subsequent oxidation of the resulting 3 molecules of acetyl-CoA is 40.

Pyruvate molecules produced by glycolysis are actively transported across the inner mitochondrial membrane, and into the matrix. Here they can be oxidized and combined with coenzyme A to form CO2, acetyl-CoA, and NADH, as in the normal cycle.

Description:

A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. The two membranes have different properties. Because of this double-membraned organization, there are five distinct parts to a mitochondrion. They are:

the outer mitochondrial membrane,
the intermembrane space (the space between the outer and inner membranes),
the inner mitochondrial membrane,
the cristae space (formed by infoldings of the inner membrane), and
the matrix (space within the inner membrane).

Mitochondria stripped of their outer membrane are called mitoplasts.

Pyruvate molecules produced by glycolysis are actively transported across the inner mitochondrial membrane, and into the matrix where they can either be oxidized and combined with coenzyme A to form CO2, acetyl-CoA, and NADH, or they can be carboxylated (by pyruvate carboxylase) to form oxaloacetate. This latter reaction” fills up” the amount of oxaloacetate in the citric acid cycle, and is, therefore, an anaplerotic reaction, increasing the cycle’s capacity to metabolize acetyl-CoA when the tissue’s energy needs (e.g. in muscle) are suddenly increased by activity.

A. Incorrect. The lytic cycle is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle.
B. Incorrect. Lysogeny is characterized by the inegration of the bacteriophage nucleic acid into the host bacterium’s genome or formations of a circular replicon in the bacterial cytoplasm.
C. Incorrect. a lytic cycle is more immediate in that it results in many copies of the virus being created very quickly and the cell is destroyed.
D. Correct. The difference between lysogenic and lytic cycles is that, in lysogenic cycles, the spread of the viral DNA occurs through the usual prokaryotic reproduction, whereas a lytic cycle is more immediate in that it results in many copies of the virus being created very quickly and the cell is destroyed.
E. Incorrect. in lysogenic cycles, the spread of the viral DNA occurs through the usual prokaryotic reproduction.

Description:

Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction (the lytic cycle is the other). Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacterium’s genome or formations of a circular replicon in the bacterial cytoplasm. In this condition, the bacterium continues to live and reproduce normally. The genetic material of the bacteriophage, called a prophage, can be transmitted to daughter cells at each subsequent cell division, and at later events (such as UV radiation or the presence of certain chemicals) can release it, causing proliferation of new phages via the lytic cycle. Lysogenic cycles can also occur in eukaryotes, although the method of DNA incorporation is not fully understood.

The difference between lysogenic and lytic cycles is that, in lysogenic cycles, the spread of the viral DNA occurs through the usual prokaryotic reproduction, whereas a lytic cycle is more immediate in that it results in many copies of the virus being created very quickly and the cell is destroyed. One key difference between the lytic cycle and the lysogenic cycle is that the lysogenic cycle does not lyse the host cell straight away. Phages that replicate only via the lytic cycle are known as virulent phages while phages that replicate using both lytic and lysogenic cycles are known as temperate phages.

In the lysogenic cycle, the phage DNA first integrates into the bacterial chromosome to produce the prophage. When the bacterium reproduces, the prophage is also copied and is present in each of the daughter cells. The daughter cells can continue to replicate with the prophage present or the prophage can exit the bacterial chromosome to initiate the lytic cycle. In the lysogenic cycle, the host DNA is not hydrolyzed but in a lytic cycle, the host DNA is hydrolyzed in the lytic phase.

Lysogenic Cycle:1. The prokaryotic cell is shown with its DNA, in green. 2. The bacteriophage attaches and releases its DNA, shown in red, into the prokaryotic cell. 3. The phage DNA then moves through the cell to the host’s DNA. 4. The phage DNA integrates itself into the host cell’s DNA, creating prophage. 5. The prophage then remains dormant until the host cell divides. 6. After the host cell has duplicated, the phage DNA in the daughter cells activates, and the phage DNA begins to express itself. Some of the cells containing the prophage go on to create new phages that will move on to infect other cells.

Alga isn’t a plant really (that is Protista) but it is a plantlike organism of any of several phyla, divisions, or classes of chiefly aquatic usually chlorophyll-containing nonvascular organisms of polyphyletic origin that usually include the green, yellow-green, brown, and red algae in the eukaryotes and especially formerly the cyanobacteria in the prokaryotes.

Description:

Vascular plants (from Latin vasculum: duct), also known as tracheophytes and also as higher plants, form a large group of plants that are defined as those land plants that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified tissue (the phloem) to conduct products of photosynthesis. Vascular plants include the club mosses, horsetails, ferns, gymnosperms (including conifers) and angiosperms (flowering plants).

A. Incorrect. Vascular plants have vascular tissues
B. Incorrect. In vascular plants, the principal generation phase is the sporophyte, which produces spores and is diploid (two sets of chromosomes per cell).
C. Incorrect. They have true roots, leaves, and stems, even if one or more of these traits are secondarily lost in some groups.
D. Incorrect. The principal generation phase is the sporophyte, which produces spores and is diploid (two sets of chromosomes per cell).
E. Correct. Vascular plants are larger in size due to the presence of a vascular system (phloem and xylem). Non-vascular plants are relatively smaller in size when compared to vascular plants.

Description:

Vascular plants are defined by three primary characteristics:
Vascular plants have vascular tissues that distribute resources through the plant. This feature allows vascular plants to evolve to a larger size than non-vascular plants, which lack these specialized conducting tissues and are thereby restricted to relatively small sizes.
In vascular plants, the principal generation phase is the sporophyte, which produces spores and is diploid (two sets of chromosomes per cell). By contrast, the principal generation phase in non-vascular plants is the gametophyte, which produces gametes and is haploid (one set of chromosomes per cell).
They have true roots, leaves, and stems, even if one or more of these traits are secondarily lost in some groups.
The formal definition of the division Tracheophyta encompasses both these characteristics in the Latin phrase “facies diploida xylem et phloem instructa” (diploid phase with xylem and phloem).
One possible mechanism for the presumed switch from emphasis on the haploid generation to emphasis on the diploid generation is the greater efficiency in spore dispersal with more complex diploid structures. In other words, elaboration of the spore stalk enabled the production of more spores and enabled the development of the ability to release them higher and to broadcast them farther. Such developments may include more photosynthetic area for the spore-bearing structure, the ability to grow independent roots, woody structure for support, and more branching.

A. Correct.
B. Incorrect. They act locally to induce vasodilation and contraction of smooth muscle.
C. Incorrect. is a derivative of glucose. It is a primary component of cell walls in fungi, the exoskeletons of arthropods, such as crustaceans
D. Incorrect. Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms.
E. Incorrect. A protein that assists non-covalent folding/unfolding in molecular biology

Description:

Lignin is a class of complex organic polymers that form key structural materials in the support tissues of vascular plants and some algae. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily. Chemically, lignins are cross-linked phenolic polymers.
Other monomers are prominent in non-woody plants.
Biological function
Lignin fills the spaces in the cell wall between cellulose, hemicellulose, and pectin components, especially in vascular and support tissues: xylem tracheids, vessel elements, and sclereid cells. It is covalently linked to hemicellulose and therefore cross-links different plant polysaccharides, conferring mechanical strength to the cell wall and by extension the plant as a whole. It is particularly abundant in compression wood but scarce in tension wood, which are types of reaction wood.
Lignin plays a crucial part in conducting water in plant stems. The polysaccharide components of plant cell walls are highly hydrophilic and thus permeable to water, whereas lignin is more hydrophobic. The crosslinking of polysaccharides by lignin is an obstacle for water absorption to the cell wall. Thus, lignin makes it possible for the plant’s vascular tissue to conduct water efficiently. Lignin is present in all vascular plants, but not in bryophytes, supporting the idea that the original function of lignin was restricted to water transport. However, it is present in red algae, which seems to suggest that the common ancestor of plants and red algae also synthesized lignin. This would suggest that its original function was structural; it plays this role in the red alga Calliarthron, where it supports joints between calcified segments. Another possibility is that the lignins in red algae and in plants are a result of convergent evolution and not of a common origin.

– Clostridium tetani is a common soil bacterium and the causative agent of tetanus. Therefore it does not have any nucleus.
– Other organisms are eukaryotic therefore they have a nucleus in their cells.

Their enzymes break down the outer membrane of the ovum, called the zona pellucida, allowing the haploid nucleus in the sperm cell to join with the haploid nucleus in the ovum.

Description:

The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is fully completed 5–10 years after testicular maturation. In Eutherian mammals the acrosome contains digestive enzymes (including hyaluronidase and acrosin). These enzymes break down the outer membrane of the ovum, called the zona pellucida, allowing the haploid nucleus in the sperm cell to join with the haploid nucleus in the ovum.
This shedding of the acrosome, or acrosome reaction, can be stimulated in vitro by substances a sperm cell may encounter naturally such as progesterone or follicular fluid, as well as the more commonly used calcium ionophore A23187. This can be done to serve as a positive control when assessing the acrosome reaction of a sperm sample by flow cytometry or fluorescence microscopy. This is usually done after staining with a fluoresceinated lectin such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46.

A. Correct. Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells. These cells are called spermatogonial stem cells.
B. Incorrect. The mitotic division of these produces two types of cells. Type A cells replenish the stem cells, and type B cells differentiate into spermatocytes.
C. Incorrect. The primary spermatocyte divides meiotically (Meiosis I) into two secondary spermatocytes; each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II.
D. Incorrect. The spermatids are transformed into spermatozoa(sperm) by the process of spermiogenesis. These develop into mature spermatozoa, also known as sperm cells.
E. Incorrect. The spermatids are transformed into mature sperms.

Description:

Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are called spermatogonial stem cells. The mitotic division of these produces two types of cells. Type A cells replenish the stem cells, and type B cells differentiate into spermatocytes. The primary spermatocyte divides meiotically (Meiosis I) into two secondary spermatocytes; each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II. The spermatids are transformed into spermatozoa(sperm) by the process of spermiogenesis. These develop into mature spermatozoa, also known as sperm cells. Thus, the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa and four haploid cells.
Spermatozoa are the mature male gametes in many sexually reproducing organisms. Thus, spermatogenesis is the male version of gametogenesis, of which the female equivalent is oogenesis. In mammals it occurs in the seminiferous tubules of the male testes in a stepwise fashion. Spermatogenesis is highly dependent upon optimal conditions for the process to occur correctly, and is essential for sexual reproduction. DNA methylation and histone modification have been implicated in the regulation of this process. It starts at puberty and usually continues uninterrupted until death, although a slight decrease can be discerned in the quantity of produced sperm with increase in age (see Male infertility).

A. Incorrect. Secrete hormones affecting pituitary gland control of spermatogenesis, particularly the polypeptide hormone, inhibin
B. Incorrect. Secrete substances initiating meiosis
C. Correct. Secrete androgen-binding protein (ABP), which concentrates testosterone in close proximity to the developing gametes
D. Incorrect. Secrete supporting testicular fluid
E. Incorrect. Secretion of anti-Müllerian hormone causes deterioration of the Müllerian duct

Description:

At all stages of differentiation, the spermatogenic cells are in close contact with Sertoli cells which are thought to provide structural and metabolic support to the developing sperm cells. A single Sertoli cell extends from the basement membrane to the lumen of the seminiferous tubule, although the cytoplasmic processes are difficult to distinguish at the light microscopic level.
Sertoli cells serve a number of functions during spermatogenesis, they support the developing gametes in the following ways:
Maintain the environment necessary for development and maturation, via the blood-testis barrier
Secrete substances initiating meiosis
Secrete supporting testicular fluid
Secrete androgen-binding protein (ABP), which concentrates testosterone in close proximity to the developing gametes
Testosterone is needed in very high quantities for maintenance of the reproductive tract, and ABP allows a much higher level of fertility
Secrete hormones affecting pituitary gland control of spermatogenesis, particularly the polypeptide hormone, inhibin
Phagocytose residual cytoplasm leftover from spermiogenesis
Secretion of anti-Müllerian hormone causes deterioration of the Müllerian duct
Protect spermatids from the immune system of the male, via the blood-testis barrier
The intercellular adhesion molecules ICAM-1 and soluble ICAM-1 have antagonistic effects on the tight junctions forming the blood-testis barrier. ICAM-2 molecules regulate spermatid adhesion on the apical side of the barrier (towards the lumen).

Labeled diagram of the organization of Sertoli cells (red) and spermatocytes (blue) in the testis. Spermatids which have not yet undergone spermiation are attached to the lumenal apex of the cell.

A. Incorrect. Hybrids may be partially sterile
B. Incorrect. Hybrids may be weak
C. Incorrect. Hybrids may be weak
D. Correct. Hybrids may be partially sterile
E. Incorrect. hybrids may be weak

Description:

Gene pool concept in crop breeding
Harlan and de Wet (1971) proposed classifying each crop and its related species by gene pools rather than by formal taxonomy.
Primary gene pool (GP-1): Members of this gene pool are probably in the same “species” (in conventional biological usage) and can intermate freely. Harlan and de Wet wrote, “Among forms of this gene pool, the crossing is easy; hybrids are generally fertile with good chromosome pairing; gene segregation is approximately normal and gene transfer is generally easy.”. They also advised subdividing each crop gene pool in two:
• Subspecies A: Cultivated races
• Subspecies B: Spontaneous races (wild or weedy)
Secondary gene pool (GP-2): Members of this pool are probably normally classified as different species than the crop species under consideration (the primary gene pool). However, these species are closely related and can cross and produce at least some fertile hybrids. As would be expected by members of different species, there are some reproductive barriers between members of the primary and secondary gene pools:
• hybrids may be weak
• hybrids may be partially sterile
• chromosomes may pair poorly or not at all
• recovery of desired phenotypes may be difficult in subsequent generations
• However, “The gene pool is available to be utilized, however, if the plant breeder or geneticist is willing to put out the effort required.”
Tertiary gene pool (GP-3): Members of this gene pool are more distantly related to the members of the primary gene pool. The primary and tertiary gene pools can be intermated, but gene transfer between them is impossible without the use of “rather extreme or radical measures” such as:
• embryo rescue (or embryo culture, a form of plant organ culture)
• induced polyploidy (chromosome doubling)
• bridging crosses (e.g., with members of the secondary gene pool).

A panmictic population is one where all individuals are potential partners. This assumes that there are no mating restrictions, neither genetic nor behavioral, upon the population, and that therefore all recombination is possible. The Wahlund effect assumes that the overall population is panmictic.

Description:

A panmictic population is one where all individuals are potential partners. This assumes that there are no mating restrictions, neither genetic nor behavioral, upon the population, and that therefore all recombination is possible. The Wahlund effect assumes that the overall population is panmictic.
In genetics, random mating involves the mating of individuals regardless of any physical, genetic, or social preference. In other words, the mating between two organisms is not influenced by any environmental, hereditary, or social interaction. Hence, potential mates have an equal chance of being selected. Random mating is a factor assumed in the Hardy-Weinberg principle and is distinct from lack of natural selection: in viability selection, for instance, selection occurs before mating.
In a panmictic species, all of the individuals of a single species are potential partners, and the species gives no mating restrictions throughout the population. Panmixia can also be referred to as random mating, referring to a population that randomly chooses their mate, rather than sorting between the adults of the population.
Panmixia allows for species to reach genetic diversity through gene flow more efficiently than monandry species. However, outside population factors, like drought and limited food sources, can affect the way any species will mate. When scientist examines species mating to understand their mating style, they look at factors like genetic markers, genetic differentiation, and gene pool.

Encephalization quotient (EQ), encephalization level (EL) or just encephalization is a relative brain size measure that is defined as the ratio between observed to predicted brain mass for an animal of a given size, based on nonlinear regression on a range of reference species. It has been used as a proxy for intelligence and thus as a possible way of comparing the intelligence of different species. For this purpose, it is a more refined measurement than the raw brain-to-body mass ratio, as it takes into account allometric effects. The relationship, expressed as a formula, has been developed for mammals, and may not yield relevant results when applied outside this group.

Incorrect. Adaptation is the dynamic evolutionary process that fits organisms to their environment, enhancing their evolutionary fitness.
Incorrect. Flexibility deals with the relative capacity of an organism to maintain itself in different habitats
Incorrect. Acclimatization occurs in a short period of time (hours to weeks), and within the organism’s lifetime (compared to adaptation, which is a development that takes place over many generations).
Incorrect. Learning is the process of acquiring new or modifying existing, knowledge, behaviors, skills, values, or preferences.
Correct. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats.

Description:

What adaptation is
Adaptation is primarily a process rather than a physical form or part of a body. [ An internal parasite (such as a liver fluke) can illustrate the distinction: such a parasite may have a very simple bodily structure, but nevertheless the organism is highly adapted to its specific environment. From this we see that adaptation is not just a matter of visible traits: in such parasites, critical adaptations take place in the life cycle, which is often quite complex. However, as a practical term, “adaptation” often refers to a product: those features of a species which result from the process. Many aspects of an animal or plant can be correctly called adaptations, though there are always some features whose function remains in doubt. By using the term adaptation for the evolutionary process, and adaptive trait for the bodily part or function (the product), one may distinguish the two different senses of the word.
Adaptation is one of the two main processes that explain the observed diversity of species, such as the different species of Darwin’s finches. The other process is speciation, in which new species arise, typically through reproductive isolation. A favorite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African lakes, where the question of reproductive isolation is complex.
Adaptation is not always a simple matter where the ideal phenotype evolves for a given external environment. An organism must be viable at all stages of its development and at all stages of its evolution. This places constraints on the evolution of development, behavior, and structure of organisms. The main constraint, over which there has been much debate, is the requirement that each genetic and phenotypic change during evolution should be relatively small because developmental systems are so complex and interlinked. However, it is not clear what “relatively small” should mean, for example, polyploidy in plants is a reasonably common large genetic change. The origin of eukaryotic endosymbiosis is a more dramatic example.
All adaptations help organisms survive in their ecological niches. The adaptive traits may be structural, behavioral or physiological. Structural adaptations are physical features of an organism, such as shape, body covering, armament, and internal organization. Behavioral adaptations are inherited systems of behavior, whether inherited in detail as instincts, or as a neuropsychological capacity for learning. Examples include searching for food, mating, and vocalizations. Physiological adaptations permit the organism to perform special functions such as making venom, secreting slime, and phototropism), but also involve more general functions such as growth and development, temperature regulation, ionic balance and other aspects of homeostasis. Adaptation affects all aspects of the life of an organism.
The following definitions are given by the evolutionary biologist Theodosius Dobzhansky:
1. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats.
2. Adaptedness is the state of being adapted: the degree to which an organism is able to live and reproduce in a given set of habitats.
3. An adaptive trait is an aspect of the developmental pattern of the organism which enables or enhances the probability of that organism surviving and reproducing.
What adaptation is not
Adaptation differs from flexibility, acclimatization, and learning. Flexibility deals with the relative capacity of an organism to maintain itself in different habitats: its degree of specialization. Acclimatization describes automatic physiological adjustments during life; learning means an improvement in behavioral performance during life. These terms are preferred to adapt for changes during life that are not inherited by the next generation.

For the transformation to take place, the recipient bacteria must be in a state of competence, which might occur in nature as a time-limited response to environmental conditions such as starvation and cell density, and may also be induced in a laboratory.

Description:

In microbiology, genetics, cell biology, and molecular biology, competence is the ability of a cell to alter its genetics by taking up extracellular (“naked”) DNA from its environment in the process called transformation. Competence may be differentiated between natural competence, a genetically specified ability of bacteria which is thought to occur under natural conditions as well as in the laboratory and induced or artificial competence, which arises when cells in laboratory cultures are treated to make them transiently permeable to DNA. Competence allows for rapid adaptation and DNA repair of the cell. This article primarily deals with natural competence in bacteria, although information about artificial competence is also provided.

A. Incorrect. Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector.
B. Incorrect. that isn’t usually a genetic term!
C. Incorrect. transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings
D. Incorrect. Blood transfusion is the process of transferring blood or blood products into one’s circulation intravenously.
E. Correct. Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. This takes place through a pilus.

Description:

Bacterial conjugation is a mechanism of horizontal gene transfer as are transformation and transduction although these two other mechanisms do not involve cell-to-cell contact.
Bacterial conjugation is often regarded as the bacterial equivalent of sexual reproduction or mating since it involves the exchange of genetic material. However, it is not sexual reproduction, since no exchange of gamete occurs, and indeed no generation of a new organism: instead an existing organism is transformed. During conjugation, the donor cell provides a conjugative or mobilizable genetic element that is most often a plasmid or transposon. Most conjugative plasmids have systems ensuring that the recipient cell does not already contain a similar element.
The genetic information transferred is often beneficial to the recipient. Benefits may include antibiotic resistance, xenobiotic tolerance or the ability to use new metabolites. Such beneficial plasmids may be considered bacterial endosymbionts. Other elements, however, may be viewed as bacterial parasites and conjugation as a mechanism evolved by them to allow for their spread.

A bacteriophage, also known informally as a phage, is a virus that infects and replicates within bacteria and archaea.

Description:

A bacteriophage is a virus that infects and replicates within bacteria and archaea.”. Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome and may have relatively simple or elaborate structures. Their genomes may encode as few as four genes and as many as hundreds of genes. Phages replicate within the bacterium following the injection of their genome into its cytoplasm. Bacteriophages are among the most common and diverse entities in the biosphere. Bacteriophages are ubiquitous viruses, found wherever bacteria exist. It is estimated there are more than 1031 bacteriophages on the planet, more than every other organism on Earth, including bacteria, combined.
Phages are widely distributed in locations populated by bacterial hosts, such as soil or the intestines of animals. One of the densest natural sources for phages and other viruses is seawater, where up to 9×108 virions per milliliter have been found in microbial mats at the surface, and up to 70% of marine bacteria may be infected by phages. They have been used for over 90 years as an alternative to antibiotics in the former Soviet Union and Central Europe as well as in France. They are seen as a possible therapy against multi-drug-resistant strains of many bacteria (see phage therapy). Nevertheless, phages of Inoviridae have been shown to complicate biofilms involved in pneumonia and cystic fibrosis and shelter the bacteria from drugs meant to eradicate disease, thus promote persistent infection.
Phage therapy
Phages were discovered to be antibacterial agents and were used in the former Soviet Republic of Georgia (pioneered there by Giorgi Eliava with help from the co-discoverer of bacteriophages, Félix d’Herelle) during the 1920s and 1930s for treating bacterial infections. They had widespread use, including the treatment of soldiers in the Red Army. However, they were abandoned for general use in the West for several reasons:
Antibiotics were discovered and marketed widely. They were easier to make, store and prescribe.
Medical trials of phages were carried out, but a basic lack of understanding raised questions about the validity of these trials.
Publication of research in the Soviet Union was mainly in the Russian or Georgian languages and was not followed internationally for many years.
The use of phages has continued since the end of the Cold War in Georgia and elsewhere in Central and Eastern Europe. The first regulated, randomized, double-blind clinical trial was reported in the Journal of Wound Care in June 2009, which evaluated the safety and efficacy of a bacteriophage cocktail to treat infected venous ulcers of the leg in human patients. The FDA approved the study as a Phase I clinical trial. The study’s results demonstrated the safety of the therapeutic application of bacteriophages but did not show efficacy. The authors explain that the use of certain chemicals that are part of standard wound care (e.g. lactoferrin or silver) may have interfered with bacteriophage viability. Another controlled clinical trial in Western Europe (treatment of ear infections caused by Pseudomonas aeruginosa) was reported shortly after this in the journal Clinical Otolaryngology in August 2009. The study concludes that bacteriophage preparations were safe and effective for the treatment of chronic ear infections in humans. Additionally, there have been numerous animal and other experimental clinical trials evaluating the efficacy of bacteriophages for various diseases, such as infected burns and wounds, and cystic fibrosis-associated lung infections, among others. Meanwhile, bacteriophage researchers are developing engineered viruses to overcome antibiotic resistance, and engineering the phage genes responsible for coding enzymes which degrade the biofilm matrix, phage structural proteins and also the enzymes responsible for lysis of the bacterial cell wall. There have been results showing that T4 phages that are small in size and short-tailed can be helpful in detecting E.coli in the human body.

Incorrect. In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U).
Incorrect. In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U).
Correct. There are many naturally occurring purines. They include the nucleobases adenine and guanine.
Incorrect. In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U).
Incorrect. In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U).

Description:

Purines and pyrimidines make up the two groups of nitrogenous bases, including the two groups of nucleotide bases. Two of the four deoxyribonucleotides (deoxyadenosine and deoxyguanosine) and two of the four ribonucleotides (adenosine, or AMP, and guanosine, or GMP), the respective building blocks of DNA and RNA, are purines. In order to form DNA and RNA, both purines and pyrimidines are needed by the cell in approximately equal quantities. Both purine and pyrimidine are self-inhibiting and activating. When purines are formed, they inhibit the enzymes required for more purine formation. This self-inhibition occurs as they also activate the enzymes needed for pyrimidine formation. Pyrimidine simultaneously self-inhibits and activates purine in a similar manner. Because of this, there is nearly an equal amount of both substances in the cell at all times.
There are many naturally occurring purines. They include the nucleobases adenine (2) and guanine (3). In DNA, these bases form hydrogen bonds with their complementary pyrimidines, thymine, and cytosine, respectively. This is called complementary base pairing. In RNA, the complement of adenine is uracil instead of thymine.
Other notable purines are hypoxanthine (4), xanthine (5), theobromine (6), caffeine (7), uric acid (8) and isoguanine (9).
Aside from the crucial roles of purines (adenine and guanine) in DNA and RNA, purines are also significant components in a number of other important biomolecules, such as ATP, GTP, cyclic AMP, NADH, and coenzyme A. Purine (1) itself, has not been found in nature, but it can be produced by organic synthesis.
They may also function directly as neurotransmitters, acting upon purinergic receptors.

purine-pyrimidine pairs are called base complements.

Description:

DNA and RNA base-pair complementarity
Complementarity is achieved by distinct interactions between nucleobases: adenine, thymine (uracil in RNA), guanine and cytosine. Adenine and guanine are purines, while thymine, cytosine, and uracil are pyrimidines. Purines are larger than pyrimidines. Both types of molecules complement each other and can only base pair with the opposing type of nucleobase. In nucleic acid, nucleobases are held together by hydrogen bonding, which only works efficiently between adenine and thymine and between guanine and cytosine. The base complement A=T shares two hydrogen bonds, while the base pair G≡C has three hydrogen bonds. All other configurations between nucleobases would hinder double helix formation. DNA strands are oriented in opposite directions, they are said to be antiparallel.
A complementary strand of DNA or RNA may be constructed based on nucleobase complementarity. Each base pair, A=T vs. G≡C, takes up roughly the same space, thereby enabling a twisted DNA double helix formation without any spatial distortions. Hydrogen bonding between the nucleobases also stabilizes the DNA double helix.
The complementarity of DNA strands in a double helix makes it possible to use one strand as a template to construct the other. This principle plays an important role in DNA replication, setting the foundation of heredity by explaining how genetic information can be passed down to the next generation. Complementarity is also utilized in DNA transcription, which generates an RNA strand from a DNA template.
DNA repair mechanisms such as proofreading are complementarity based and allow for error correction during DNA replication by removing mismatched nucleobases.
Nucleic acid strands may also form hybrids in which single-stranded DNA may readily anneal with complementary DNA or RNA. This principle is the basis of commonly performed laboratory techniques such as the polymerase chain reaction, PCR.
Two strands of a complementary sequence are referred to as sense and anti-sense. The sense strand is, generally, the transcribed sequence of DNA or the RNA that was generated in transcription. While the anti-sense strand is the strand that is complementary to the sense sequence.

The genome size of organisms is shown below:

As shown, plants have the largest genome size on average.

A. Incorrect. A chromosome is a deoxyribonucleic acid (DNA) molecule with part or all of the genetic material (genome) of an organism.
B. Incorrect. An allele is a variant form of a given gene.
C. Incorrect. Ploidy is the number of complete sets of chromosomes in a cell
D. Incorrect. The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids
E. Correct. Dyad is a pair of sister chromatids

Description:

Chromatids maybe a sister or non-sister chromatids. A sister chromatid is either one of the two chromatids of the same chromosome joined together by a common centromere. A pair of sister chromatids is called a dyad. Once sister chromatids have separated (during the anaphase of mitosis or the anaphase II of meiosis during sexual reproduction), they are again called chromosomes. Although having the same genetic mass as the individual chromatids that made up its parent, the daughter “molecules” are called chromosomes in a similar way that one child of a pair of twins is not referred to as a single twin. The DNA sequence of two sister chromatids is completely identical (apart from very rare DNA copying errors).
Sister chromatid exchange (SCE) is the exchange of genetic information between two sister chromatids. SCEs can occur during mitosis or meiosis. SCEs appear to primarily reflect DNA recombinational repair processes responding to DNA damage (see articles Sister chromatids and Sister chromatid exchange).
Non-sister chromatids, on the other hand, refers to either of the two chromatids of paired homologous chromosomes, that is, the pairing of a paternal chromosome and a maternal chromosome. In chromosomal crossovers, non-sister (homologous) chromatids form chiasmata to exchange genetic material during the prophase I of meiosis (See Homologous recombination).

A. Incorrect. Canavan disease is characterized by the degeneration of myelin in the phospholipid layer insulating the axon of a neuron and is associated with a gene located on human chromosome 17.
B. Incorrect. Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of the third copy of chromosome 21.
C. Correct. Klinefelter syndrome (KS) also known as 47, XXY or XXY, is the set of symptoms that result from two or more X chromosomes in males.
D. Incorrect. Cri du chat is a rare genetic disorder due to chromosome deletion on chromosome 5.
E. Incorrect. The most common cause of CMT (70–80% of the cases) is the duplication of a large region on the short arm of chromosome 17 that includes the gene PMP22.

Description:

Klinefelter syndrome (KS) also known as 47, XXY or XXY, is the set of symptoms that result from two or more X chromosomes in males. The primary features are infertility and small testicles. Often, symptoms may be subtle and many people do not realize they are affected. Sometimes, symptoms are more prominent and may include weaker muscles, greater height, poor coordination, less body hair, breast growth, and less interest in sex. Often it is only at puberty that these symptoms are noticed. Intelligence is usually normal; however, reading difficulties and problems with speech are more common. Symptoms are typically more severe if three or more X chromosomes are present (XXXY syndrome or 49, XXXXY).
Klinefelter syndrome usually occurs randomly. An older mother may have a slightly increased risk of a child with KS. The condition is not typically inherited from one’s parents. The underlying mechanisms involve at least one extra X chromosome in addition to a Y chromosome such that the total chromosome number is 47 or more rather than the usual 46. KS is diagnosed by the genetic test known as a karyotype.
While no cure is known, a number of treatments may help. Physical therapy, speech and language therapy, counseling, and adjustments of teaching methods may be useful. Testosterone replacement may be used in those who have significantly lower levels. Enlarged breasts may be removed by surgery. About half of affected males have a chance of fathering children with the help of assisted reproductive technology, but this is expensive and not risk-free. Males appear to have a higher risk of breast cancer than typical, but still lower than that of females. People with the condition have a nearly normal life expectancy.
Klinefelter syndrome is one of the most common chromosomal disorders, occurring in one to two per 1,000 live male births. It is named after Harry Klinefelter, who identified the condition in the 1940s. In 1956, identification of the extra X chromosome was first noticed. Mice can also have XXY syndrome, making them a useful research model.

A. Incorrect. In anatomy, the G cell or gastrin cell is a type of cell in the stomach and duodenum that secretes gastrin. It works in conjunction with gastric chief cells and parietal cells.
B. Correct. The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B12.
C. Incorrect. A gastric chief cell is a type of cell in the stomach that releases pepsinogen and gastric lipase and is the cell responsible for the secretion of chymosin in ruminants.
D. Incorrect. The pylorus is one component of the gastrointestinal system. Food from the stomach, as chyme, passes through the pylorus to the duodenum. The pylorus, through the pyloric sphincter, regulates the entry of food from the stomach into the duodenum.
E. Incorrect. cardia is the last part of the esophagus.

Description:

Intrinsic factor (IF), also known as a gastric intrinsic factor (GIF), is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B12 later on in the ileum of the small intestine. In humans, the gastric intrinsic factor protein is encoded by the GIF gene.
Haptocorrin (also known as HC, R protein, and transcobalamin I, TCN1) is another glycoprotein secreted by the salivary glands which bind to vitamin B12. Vitamin B12 is acid sensitive and in binding to transcobalamin I it can safely pass through the acidic stomach to the duodenum. In the less acidic environment of the small intestine, pancreatic enzymes digest the glycoprotein carrier and vitamin B12 can then bind to intrinsic factor. This new complex is then absorbed by the epithelial cells (enterocytes) of the ileum. Inside the cells, B12 dissociates once again and binds to another protein, transcobalamin II (TCN2); the new complex can then exit the epithelial cells to be carried to the liver.
Site of secretion
The intrinsic factor is secreted by the stomach, and so is present in the gastric juice as well as in the gastric mucous membrane. The optimum pH for its action is approximately 7. Its concentration does not correlate with the amount of HCl or pepsin in the gastric juice, e.g., an intrinsic factor may be present even when pepsin is largely absent. The site of formation of the intrinsic factor varies in different species. In pigs it is obtained from the pylorus and beginning of the duodenum; in human beings, it is present in the fundus and body of the stomach.
The limited amount of normal human gastric intrinsic factor limits normal efficient absorption of B12 to about 2 μg per meal, a nominally adequate intake of B12.

A. Correct. The fundus is formed in the upper curved part.
B. Incorrect. The body is the main, central region of the stomach.
C. Incorrect. The angular incisure (or angular notch) is a small notch on the stomach. It is located on the lesser curvature of the stomach near the pyloric end. Its location varies depending on how distended the stomach is.
D. Incorrect. The pylorus is the lower section of the stomach that empties contents into the duodenum.
E. Incorrect. The pylorus is the lower section of the stomach that empties contents into the duodenum.

Description:

In humans, the stomach lies between the oesophagus and the duodenum (the first part of the small intestine). It is in the left upper part of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying behind the stomach is the pancreas. A large double fold of visceral peritoneum called the greater omentum hangs down from the greater curvature of the stomach. Two sphincters keep the contents of the stomach contained; the lower oesophageal sphincter (found in the cardiac region), at the junction of the oesophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum.
The stomach is surrounded by parasympathetic (a stimulant) and sympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.
In adult humans, the stomach has a relaxed, near the empty volume of about 75 millilitres. Because it is a distensible organ, it normally expands to hold about one litre of food. The stomach of a newborn human baby will only be able to retain about 30 millilitres.
Sections
In classical anatomy the human stomach is divided into four sections, beginning at the cardia, each of which has different cells and functions.
The cardia is where the contents of the oesophagus empty into the stomach.
The fundus is formed in the upper curved part.
The body is the main, central region of the stomach.
The pylorus is the lower section of the stomach that empties contents into the duodenum.
The cardia is defined as the region following the “z-line” of the gastroesophageal junction, the point at which the epithelium changes from stratified squamous to columnar. Near the cardia is the lower oesophageal sphincter. Recent research has shown that the cardia is not an anatomically distinct region of the stomach but a region of the oesophageal lining damaged by reflux.

Gastrin releases in response to certain stimuli. Such as:
stomach antrum distension
vagal stimulation (mediated by the neurocrine bombesin, or GRP in humans)
the presence of partially digested proteins, especially amino acids, in the stomach. Aromatic amino acids are particularly powerful stimuli for gastrin release.
hypercalcemia (via calcium-sensing receptors)
Gastrin release is inhibited by:
the presence of acid (primarily the secreted HCl) in the stomach (a case of negative feedback)
somatostatin also inhibits the release of gastrin, along with secretin, GIP (gastroinhibitory peptide), VIP (vasoactive intestinal peptide), glucagon and calcitonin

A. Incorrect. Among people with diabetes, prevention is by matching the foods eaten with the amount of exercise and the medications used. When people feel their blood sugar is low, testing with a glucose monitor is recommended. Some people have few initial symptoms of low blood sugar, and frequent routine testing in this group is recommended. Treatment of hypoglycemia is by eating foods high in simple sugars or taking dextrose. If a person is not able to take food by mouth, an injection of glucagon may help.
B. Incorrect. Adrenaline, also known as adrenalin or epinephrine, is a hormone, neurotransmitter, and medication. Epinephrine is normally produced by both the adrenal glands and certain neurons. It plays an important role in the fight-or-flight response by increasing blood flow to muscles, the output of the heart, pupil dilation response, and blood sugar level.
C. Correct. Secretion of glucagon is inhibited by:
Somatostatin
Insulin (via GABA)
PPARγ/retinoid X receptor heterodimer.
Increased free fatty acids and keto acids into the blood.
Increased urea production
Glucagon-like peptide-1
D. Incorrect. Arginine, also known as L-arginine, is an α-amino acid that is used in the biosynthesis of proteins.
E. Incorrect. often from muscle-derived pyruvate/glutamate transamination

Description:

The hormone is synthesized and secreted from alpha cells (α-cells) of the islets of Langerhans, which are located in the endocrine portion of the pancreas. Production, which is otherwise freerunning, is suppressed/regulated by insulin from the adjacent beta cells. (Actually, GABA is the interlock signal chemical that prevents simultaneous insulin and glucagon production in the pancreas. It is produced by the pancreatic ß cells at the same time insulin is being produced. It prevents the α cells from being switched on.)
When blood sugar drops, insulin production drops and more glucagon is produced In rodents, the alpha cells are located in the outer rim of the islet. The human islet structure is much less segregated, and alpha cells are distributed throughout the islet in close proximity to beta cells. Glucagon is also produced by alpha cells in the stomach.
Recent research has demonstrated that glucagon production may also take place outside the pancreas, with the gut being the most likely site of extrapancreatic glucagon synthesis.
Regulation
Secretion of glucagon is stimulated by:
Hypoglycemia
Epinephrine (via β2, α2, and α1 adrenergic receptors)
Arginine
Alanine
Acetylcholine
Cholecystokinin
Gastric inhibitory polypeptide
Secretion of glucagon is inhibited by:

Somatostatin
Insulin (via GABA)
PPARγ/retinoid X receptor heterodimer.
Increased free fatty acids and keto acids into the blood.
Increased urea production
Glucagon-like peptide-1
Structure
Glucagon is a 29-amino acid polypeptide. Its primary structure in humans is NH2-His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Ser-Arg-Arg-Ala-Gln-Asp-Phe-Val-Gln-Trp-Leu-Met-Asn-Thr-COOH.
The polypeptide has a molecular weight of 3485 daltons. Glucagon is a peptide (nonsteroid) hormone.
Glucagon is generated from the cleavage of proglucagon by proprotein convertase 2 in pancreatic islet α cells. In intestinal L cells, proglucagon is cleaved to the alternate products glicentin, GLP-1 (an incretin), IP-2, and GLP-2 (promotes intestinal growth).

Description:

epinephrine acts on nearly all body tissues. Its actions vary by tissue type and tissue expression of adrenergic receptors. For example, high levels of epinephrine cause smooth muscle relaxation in the airways but cause contraction of the smooth muscle that lines most arterioles.
Epinephrine acts by binding to a variety of adrenergic receptors. Epinephrine is a nonselective agonist of all adrenergic receptors, including the major subtypes α1, α2, β1, β2, and β3. Epinephrine’s binding to these receptors triggers a number of metabolic changes. Binding to α-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis in the liver and muscle, and stimulates glycolysis and inhibits insulin-mediated glycogenesis in muscle. β adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue. Together, these effects lead to increased blood glucose and fatty acids, providing substrates for energy production within cells throughout the body.

Its actions are to increase peripheral resistance via α1 receptor-dependent vasoconstriction and to increase cardiac output via its binding to β1 receptors. The goal of reducing peripheral circulation is to increase coronary and cerebral perfusion pressures and therefore increase oxygen exchange at the cellular level. While epinephrine does increase aortic, cerebral, and carotid circulation pressure, it lowers carotid blood flow and end-tidal CO2 or ETCO2 levels. It appears that epinephrine may be improving macrocirculation at the expense of the capillary beds where actual perfusion is taking place.

α1 antagonists can be used for treating:
hypertension – decrease blood pressure by decreasing peripheral vasoconstriction
benign prostate hyperplasia – relax smooth muscles within the prostate thus easing urinationSENTIALS

Description:

α receptors
α receptors have actions in common, but also individual effects. Common (or still receptor unspecified) actions include:

vasoconstriction
decreased motility of smooth muscle in the gastrointestinal tract
Subtype unspecific α agonists (see actions above) can be used to treat rhinitis (they decrease mucus secretion). Subtype unspecific α antagonists can be used to treat pheochromocytoma (they decrease vasoconstriction caused by norepinephrine).

α1 receptor
Main article: Alpha-1 adrenergic receptor
α1-adrenoreceptors are members of the Gq protein-coupled receptor superfamily. Upon activation, a heterotrimeric G protein, Gq, activates phospholipase C (PLC). The PLC cleaves phosphatidylinositol 4,5-bisphosphate (PIP2), which in turn causes an increase in inositol triphosphate (IP3) and diacylglycerol (DAG). The former interacts with calcium channels of the endoplasmic and sarcoplasmic reticulum, thus changing the calcium content in a cell. This triggers all other effects, including a prominent slow after depolarizing current (sADP) in neurons.

Actions of the α1 receptor mainly involve smooth muscle contraction. It causes vasoconstriction in many blood vessels, including those of the skin, gastrointestinal system, kidney (renal artery) and brain. Other areas of smooth muscle contraction are:

ureter
vas deferens
hair (arrector pili muscles)
uterus (when pregnant)
urethral sphincter
urothelium and lamina propria
bronchioles (although minor relative to the relaxing effect of β2 receptor on bronchioles)
blood vessels of the ciliary body (stimulation causes mydriasis)
Actions also include glycogenolysis and gluconeogenesis from adipose tissue and liver; secretion from sweat glands and Na+ reabsorption from the kidney.

α1 antagonists can be used to treat:
hypertension – decrease blood pressure by decreasing peripheral vasoconstriction
benign prostate hyperplasia – relax smooth muscles within the prostate thus easing urination
α2 receptor
Main article: Alpha-2 adrenergic receptor
The α2 receptor couples to the Gi/o protein. It is a presynaptic receptor, causing negative feedback on, for example, norepinephrine (NE). When NE is released into the synapse, it feeds back on the α2 receptor, causing less NE release from the presynaptic neuron. This decreases the effect of NE. There are also α2 receptors on the nerve terminal membrane of the post-synaptic adrenergic neuron.

Actions of the α2 receptor include:
decreased insulin release from the pancreas
increased glucagon release from the pancreas
contraction of sphincters of the GI-tract
negative feedback in the neuronal synapses – presynaptic inhibition of norepinephrine release in CNS
increased platelet aggregation (increased blood clotting tendency)
decreases peripheral vascular resistance
α2 agonists (see actions above) can be used to treat:

hypertension – decrease blood pressure raising actions of the sympathetic nervous system
α2 antagonists can be used to treat:

impotence – relax penile smooth muscles and ease blood flow
depression – enhance mood by increasing norepinephrine secretion
β receptors
Subtype unspecific β agonists can be used to treat:

heart failure – increase cardiac output acutely in an emergency
circulatory shock – increase cardiac output thus redistributing blood volume
anaphylaxis – bronchodilation
Subtype unspecific β antagonists (beta-blockers) can be used to treat:

heart arrhythmia – decrease the output of sinus node thus stabilizing heart function
coronary artery disease – reduce heart rate and hence increasing oxygen supply
heart failure – prevent sudden death related to this condition, which is often caused by ischemias or arrhythmias
hyperthyroidism – reduce peripheral sympathetic hyperresponsiveness
migraine – reduce the number of attacks
stage fright – reduce tachycardia and tremor
glaucoma – reduce intraocular pressure.

The endogenous production of insulin affected in all of the following:
At transcription from the insulin gene
In mRNA stability
At the mRNA translation
In the posttranslational modifications

Description:

Insulin is produced in the pancreas and the Brockmann body (in some fish), and released when any of several stimuli are detected. These stimuli include ingested protein and glucose in the blood produced from digested food. Carbohydrates can be polymers of simple sugars or the simple sugars themselves. If the carbohydrates include glucose, then that glucose will be absorbed into the bloodstream and blood glucose level will begin to rise. In target cells, insulin initiates signal transduction, which has the effect of increasing glucose uptake and storage. Finally, insulin is degraded, terminating the response.
Insulin undergoes extensive posttranslational modification along the production pathway. Production and secretion are largely independent; prepared insulin is stored awaiting secretion. Both C-peptide and mature insulin are biologically active. Cell components and proteins in this image are not to scale.
In mammals, insulin is synthesized in the pancreas within the beta cells. One million to three million pancreatic islets form the endocrine part of the pancreas, which is primarily an exocrine gland. The endocrine portion accounts for only 2% of the total mass of the pancreas. Within the pancreatic islets, beta cells constitute 65–80% of all the cells.
Insulin consists of two polypeptide chains, the A- and B- chains, linked together by disulfide bonds. It is however first synthesized as a single polypeptide called preproinsulin in beta cells. Preproinsulin contains a 24-residue signal peptide which directs the nascent polypeptide chain to the rough endoplasmic reticulum (RER). The signal peptide is cleaved as the polypeptide is translocated into the lumen of the RER, forming proinsulin. In the RER the proinsulin folds into the correct conformation and 3 disulfide bonds are formed. About 5–10 min after its assembly in the endoplasmic reticulum, proinsulin is transported to the trans-Golgi network (TGN) where immature granules are formed. Transport to the TGN may take about 30 min.
Proinsulin undergoes maturation into active insulin through the action of cellular endopeptidases known as prohormone convertases (PC1 and PC2), as well as the exoprotease carboxypeptidase E. The endopeptidases cleave at 2 positions, releasing a fragment called the C-peptide, and leaving 2 peptide chains, the B- and A- chains, linked by 2 disulfide bonds. The cleavage sites are each located after a pair of basic residues (lysine-64 and arginine-65, and arginine-31 and −32). After cleavage of the C-peptide, these 2 pairs of basic residues are removed by the carboxypeptidase. The C-peptide is the central portion of proinsulin, and the primary sequence of proinsulin goes in the order “B-C-A” (the B and A chains were identified on the basis of mass and the C-peptide was discovered later).
The resulting mature insulin is packaged inside mature granules waiting for metabolic signals (such as leucine, arginine, glucose, and mannose) and vagal nerve stimulation to be exocytosed from the cell into the circulation.
The endogenous production of insulin is regulated in:
At transcription from the insulin gene
In mRNA stability
At the mRNA translation
In the posttranslational modifications
Insulin and its related proteins have been shown to be produced inside the brain, and reduced levels of these proteins are linked to Alzheimer’s disease.
Insulin release is stimulated also by beta-2 receptor stimulation and inhibited by alpha-1 receptor stimulation. In addition, cortisol, glucagon and growth hormone antagonize the actions of insulin during times of stress. Insulin also inhibits fatty acid release by hormone-sensitive lipase in adipose tissue.

α alpha cells secrete glucagon (increase glucose in the blood), β beta cells secrete insulin (decrease glucose in the blood), δ delta cells secrete somatostatin (regulates/stops α and β cells) and PP cells, or γ (gamma) cells, secrete pancreatic polypeptide.

Description:

Approximately 3 million cell clusters called pancreatic islets are present in the pancreas. Within these islets are four main types of cells that are involved in the regulation of blood glucose levels. Each type of cell secretes a different type of hormone: α alpha cells secrete glucagon (increase glucose in the blood), β beta cells secrete insulin (decrease glucose in the blood), δ delta cells secrete somatostatin (regulates/stops α and β cells) and PP cells, or γ (gamma) cells, secrete pancreatic polypeptide. These act to control blood glucose through secreting glucagon to increase the levels of glucose, and insulin to decrease it.
The islets are crisscrossed by a dense network of capillaries. The capillaries of the islets are lined by layers of islet cells, and most endocrine cells are in direct contact with blood vessels, either by cytoplasmic processes or by direct apposition. The islets function independently from the digestive role played by the majority of pancreatic cells.
The activity of the cells in the islets is affected by the autonomic nervous system:
Sympathetic (adrenergic)
α2: decreases secretion from beta cells, increases secretion from alpha cells, β2: increases secretion from beta cells
Parasympathetic (muscarinic)
M3: increases stimulation of alpha cells and beta cells

Systems biology is the computational and mathematical analysis and modeling of complex biological systems. The science that could cover all of these fields is bioinformatics which is a mixture of mathematical, computational and biological methods.