Also found in: Dictionary, Thesaurus, Legal, Financial, Encyclopedia, Wikipedia.
a succession or recurring series of events.
cardiac cycle a complete cardiac movement, or heart beat, including systole, diastole, and the intervening pause.
cell cycle the cycle of biochemical and morphological events occurring in a reproducing cell population; it consists of the S phase, occurring toward the end of interphase, in which DNA is synthesized; the G2 phase, a relatively quiescent period; the M phase, consisting of the four phases of mitosis; and the G1 phase of interphase, which lasts until the S phase of the next cycle.
citric acid cycle tricarboxylic acid cycle.
estrous cycle the recurring periods of estrus in adult females of most mammalian species and the correlated changes in the reproductive tract from one period to another.
hair cycle the successive phases of the production and then loss of hair, consisting of anagen, catagen, and telogen.
Krebs cycle tricarboxylic acid cycle.
menstrual cycle see menstrual cycle.
ovarian cycle the sequence of physiologic changes in the ovary involved in ovulation; see also ovulation and reproduction.
reproductive cycle the cycle of physiologic changes in the reproductive organs, from the time of fertilization of the ovum through gestation and childbirth; see also reproduction.
sex cycle (sexual cycle)
1. the physiologic changes that recur regularly in the reproductive organs of nonpregnant female mammals.
2. the period of sexual reproduction in an organism that also reproduces asexually.
TCA cycle tricarboxylic acid cycle.
tricarboxylic acid cycle the cyclic metabolic mechanism by which the complete oxidation of the acetyl portion of acetyl-coenzyme A is effected; the process is the chief source of mammalian energy, during which carbon chains of sugars, fatty acids, and amino acids are metabolized to yield carbon dioxide, water, and high-energy phosphate bonds. Called also citric acid cycle, Krebs cycle, and TCA cycle.
urea cycle a cyclic series of reactions that produce urea; it is a major route for removal of the ammonia produced in the metabolism of amino acids in the liver and kidney.
ox·a·lo·a·ce·tic ac·id(ok'să-lō-ă-sē'tik as'id),
A ketodicarboxylic acid (HOOCCH2COCOOH) and important intermediate in the tricarboxylic acid cycle; the product formed when l-aspartate acts as an amine donor in transamination reactions.
oxaloacetic acid/ox·a·lo·ace·tic ac·id/ (ok″sah-lo-ah-sēt´ik) a metabolic intermediate in the tricarboxylic acid cycle; it is convertible to aspartic acid by aspartate transaminase.
oxaloacetic acid(ŏk′sə-lō-ə-sē′tĭk, ŏk-săl′ō-) or
oxalacetic acid(ŏk-săl′ə-sē′tĭk, ŏk′sə-lə-)
A colorless crystalline dicarboxylic acid, C4H4O5, that is formed by oxidation of malic acid in the Krebs cycle and by transamination from aspartic acid. It is important as an intermediate in the metabolism of carbohydrates and a precursor in the synthesis of amino acids.
ox·a·lo·a·ce·tic ac·id(ok'să-lō-ă-sē'tik as'id)
A ketodicarboxylic acid and important intermediate in the tricarboxylic acid cycle.
oxaloacetic acida dicarboxylic acid that condenses with acetlycoenzyme A, forming citric acid (citrate) and CoA, thus initiating the KREBS CYCLE.
a metabolic intermediate in the tricarboxylic acid cycle, which is also a substrate of aspartate aminotransferase.