TEST BANK FOR Campbell Biology 9th Edition Glossary A+GRADED 2023

TEST BANK FOR Campbell Biology 9th Edition Glossary A+GRADED 2023. 5′ cap - A modified form of guanine nucleotide added onto the 5′ end of a pre-mRNA molecule. A site - One of a ribosome's three binding sites for tRNA during translation. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.) ABC hypothesis - A model of flower formation identifying three classes of organ identity genes that direct formation of the four types of floral organs. abiotic - Nonliving; referring to the physical and chemical properties of an environment. abortion - The termination of a pregnancy in progress. abscisic acid (ABA) - A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance. absorption - The third stage of food processing in animals: the uptake of small nutrient molecules by an organism's body. absorption spectrum - The range of a pigment's ability to absorb various wavelengths of light; also a graph of such a range. abyssal zone - The part of the ocean's benthic zone between 2,000 and 6,000 m deep. acanthodian - Any of a group of ancient jawed aquatic vertebrates from the Silurian and Devonian periods. accessory fruit - A fruit, or assemblage of fruits, in which the fleshy parts are derived largely or entirely from tissues other than the ovary. acclimatization - Physiological adjustment to a change in an environmental factor. acetyl coenzyme A (acetyl CoA) - The entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme. acetylcholine - One of the most common neurotransmitters; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane.