| 释义 |
urea cycle
urea cycle n (Biochemistry) the sequence of metabolic reactions leading in vertebrates to the synthesis of urea EncyclopediaSeecycleurea cycle
cycle [si´k'l] a succession or recurring series of events.cardiac cycle a complete cardiac movement, or heart beat, including systole, diastole, and the intervening pause. Cardiac cycle. From Applegate, 2000.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. Central pathways of metabolism: How the body produces energy from the energy-containing nutrients using the tricarboxylic acid cycle. From Davis and Sherer, 1994.urea cycle a cyclic series of reactions that produce urea" >urea; it is a major route for removal of the ammonia produced in the metabolism of amino acids in the liver and kidney.u·re·a cy·clethe sequence of chemical reactions, occurring primarily in the liver, that results in the production of urea; the key reaction is the hydrolysis of l-arginine by arginase to l-ornithine and urea; l-ornithine is then converted to l-citrulline by a carbamoylation reaction, then to l-argininosuccinate by an amination reaction involving l-aspartic acid; finally, a lyase-dependent step generates arginine and fumarate. Synonym(s): Krebs-Henseleit cycle, Krebs ornithine cycle, Krebs urea cycle, ornithine cycleurea cyclen. The sequence of chemical reactions occurring in the liver that results in the production of urea. The key reaction is the hydrolysis of arginine by arginase to ornithine and urea.urea cycle see ORNITHINE CYCLE.Krebs, Sir Hans Adolph, German biochemist in England and Nobel laureate, 1900-1981. Krebs cycle - together with oxidative phosphorylation, the main source of energy in the mammalian body and the end toward which carbohydrate, fat, and protein metabolism are directed. Synonym(s): tricarboxylic acid cycleKrebs-Henseleit cycle - the sequence of chemical reactions, occurring primarily in the liver, that results in the production of urea. Synonym(s): urea cycleKrebs-Ringer solution - a modification of Ringer solution.FinancialSeeCycle |