PNB 2250 Lecture Notes - Lecture 25: Urea Cycle, Ornithine, Guanine
31 Oct 2016
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Document Summary
Metabolism: produces nitrogenous wastes, co2, and acid, four main forms. Pathway: amino acid- keto acids- uric acid- allantoin. Amino acids to keto acid to ammonia: arginase. Deaminase: ubiquitous (all animals) have in liver or kidney, nucleic acids are also deaminated giving rise to ammonia, xanthine and hypoxanthine. Bird and reptiles: there is no phylogenic relationship between groups and types of secretions. Different choices: represents environment, water- ammonia. Limited concentration in urine: terrestrial- urea. High concentration in urine: acid- uric acid. Mode of secretion: environmentally based (water, air, etc. , coupled to water balance. The nature of n-excretion is a direct indication of the type of environment that an animal lives in. Requires expression of the enzymatic pathway needed for a particular type of n-excretion. Uric acid secretion requires 15 enzymatic steps. Ammonia: produced by amino acid metabolism (deamination, secreted directly into water (toxic) Leads to fish tank odor: small, highly soluble in water, rapidly diffuses.
