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46 Cards in this Set
- Front
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ABO blood group |
A set of four phenotypes produced by different combinations of three alleles at a single locus; blood types are A, B, AB, and O, depending on which alleles are expressed as antigens on the red blood cell surface. |
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Abscission |
In vascular plants, the dropping of leaves, flowers, fruits, or stems at the end of the growing season, as the result of the formation of a layer of specialized cells (the abscission zone) and the action of a hormone (ethylene) |
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Absorption spectrum |
The relationship of absorbance vs. wavelength for a pigment molecule. This indicates which wavelength are absorbed maximally by a pigment. For example, chlorophyll a absorbs most strongly in the violet-blue and red regions of the visible light spectrum. |
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Acceptor stem |
The 3' end of a tRNA molecule; the portion that amino acids become attached to during the tRNA charging reaction. |
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Accessory pigment |
A secondary light-absorbing pigment used in photosynthesis, including chlorophyll b and the carotenoids, that complement the absorption spectrum of chlorophyll a. |
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Accolomate |
An animal, such as a flatworm, having a body plan that has no body cavity; the space between mesoderm and endoderm is filled with cells and organic material. |
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Acetyl-CoA |
The product of the transition reaction between glycolysis and the Krebs cycle. Pyruvate is oxidized to acetyl-CoA by NAD, also producing CO2 and NADH. |
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Achiasmate segregation |
The lining up and subsequent separation of homologues during meiosis I without the formation of chiasmata between homologues; found in Drosophila males and some other species. |
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Acid |
Any substance that dissociates in water to increase the hydrogen ion concentration and thus lower the pH. |
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Actin |
One of the two major proteins that make up vertebrate muscle; the other is myosin. |
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Action potential |
A transient, all-or-none reversal of the electric potential across a membrane; in neurons, an action potential initiates transmission of a nerve impulse. |
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Action spectrum |
A measure of the efficiency of different wavelengths of light for photosynthesis. In plants it corresponds to the absorption spectrum of chlorophylls. |
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Activation energy |
The energy that must be processed by a molecule in order for it to undergo a specific chemical reaction. |
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Active site |
The region of an enzyme surface to which a specific set of substrates binds, lowering the activation energy required for a particular chemical reaction and so facilitating it. |
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Active transport |
The pumping of individual ions or other molecules across a cellular membrane from a region of lower concentration to one of higher concentration (i.e., against a concentration gradient), this transport process requires energy, which is typically supplied by the expenditure of ATP. |
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Adaptation |
A peculiarity of structure, physiology, or behavior that promotes the likelihood of an organism's survival and reproduction in a particular environment. |
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Adapter protein |
Any of a class of proteins that acts as a link between a receptor and other proteins to initiate signal transduction. |
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Adaptive radiation |
The evolution of several divergent forms from a primitive and unspecialized ancestor. |
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Adenosine triphosphate (ATP) |
The nucleotide consisting of adenine, ribose sugar, and three phosphate groups; the energy currency of cellular metabolism in all organisms. |
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Adherins junction |
An anchoring junction that connects the actin filaments of one cell with those of adjacent cells or with the extracellular matrix. |
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ATP synthase |
The enzyme responsible for producing ATP in oxidative phosphorylation; it uses the energy from a proton gradient to catalyze the reaction ADP+P to ATP. |
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Adenylyl cylase |
An enzyme that produces large amounts of cAMP from ATP; the cAMP acts as a second messenger in a target cell. |
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Adhesion |
The tendency of water to cling to other polar compounds due to hydrogen bonding |
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Adipose cells |
Fat cells, found in loose connective tissue, usually in large groups that form adipose tissue. Each cell can store a droplet of fat (triglyceride) |
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Adventitious |
Referring to a structure arising from an unusual place, such as stems from roots or roots from stems |
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Aerenchyma |
In plants. loose parenchymal tissue with large air spaces in it; often found in plants that grow in water |
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Aerobic |
Requiring free oxygen; any biological process that can occur in the presence or gaseous oxygen |
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Aerobic respiration |
The process that results in the complete oxidation of glucose using oxygen as the final electron acceptor. Oxygen acts as the final electron acceptor for an electron transport chain that produces a proton gradient for the chemiosmotic synthesis of ATP |
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Aleurone |
In plants, the outer layer of the endosperm in a seed; on germination, produces a-amylase that breaks down the carbohydrates of the endosperm to nourish the embryo |
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Alga / Algae |
A unicellular or simple multicellular photosynthetic organism lacking multicellular sex organs |
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Allantois |
A membrane of the amniotic egg that functions in respiration and excretion in birds and reptiles and plays an important role in the development of the placenta in most mammals |
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Allele |
One of two or more alternative states of a gene |
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Allele frequency |
A measure of the occurrence of an allele in a population, expressed as proportion of the entire population, for example, an occurrence of 0.84 (84%) |
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Allometric growth |
A pattern of growth in which different components grow at different rates |
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Allelopathy |
The release of a substance from the roots of one plant that block the germination of nearby seeds or inhibits the growth of a neighboring plant |
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Allopatric speciation |
The differentiation of geographically isolated populations into distinct species |
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Allopolyploid |
A polyploid organism that contains the genomes of two or more different species |
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Allosteric activator |
A substance that binds to an enzyme's allosteric site and keeps the enzyme in its active configuration |
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Allosteric inhibitor |
A noncompetitive inhibitor that binds to an enzyme's allosteric site and prevents the enzyme from changing to its active configuration |
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Allosteric site |
A part of an enzyme, away from its active site, that serves as an on/off switch for the function of the enzyme |
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Alpha (a) helix |
A form of secondary structure in proteins where the polypeptide chain is wound into a spiral due to interactions between amino and corboxyl groups in the peptide backbone |
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Alternation of generations |
A reproductive cycle in which the haploid (n) phase (the gametophyte), gives rise to gametes, which, after fusion to form a zygote, germinate to produce a diploid (2n) phase (the sporophyte). Spores produced be meiotic division from the sporophyte give rise to new gametophytes, completing the cycle |
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Alternative splicing |
In eukaryotes, the production of different mRNAs from a single primary transcript be including different sets of exons |
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Altruism |
Self-sacrifice for the benefit of others; in formal terms, the behavior that increases the fitness of the recipient while reducing the fitness of the altruistic individual |
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Alveolus / Alveoli |
One of many small, thin-walled air sacs within the lungs in which the bronchioles terminate |
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Amino acid |
The subunit structure from which proteins are produced, consisting of a central carbon atom with a carboxyl group (-COOH), an amino group (-NH2), a hydrogen, and a side group (R group); only the side group differs from one amino acid to another |
