CHEM 153C Study Guide - Final Guide: Ammonia, Carbamoyl Phosphate, Pyridoxal Phosphate
23 Jun 2016
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_essential amino acids must be obtained from the diet. Degrade no longer needed or abnormal proteins or nucleic acids. Degrade proteins (especially muscle) during periods of extreme nutritional stress. _ubiquinin-coo- + enz-sh + atp ------- ubiquinin-co-s-enz + amp +ppi. _ coupling of ubiquitin and condemned protein requires energy. Formation of thioester captures the energy of phosphoanhydride bond cleavage to be used in bond formation. _ thioester of ubiquitin-e1 is cleaved as amide link between ubiquitin and condemned protein is formed. The thermodynamic favorability of thioester cleavage makes possible the formation of the amide link. Various organisms store amino acids to provide nitrogen during times of nutrient (nitrogen) limitation. To avoid the osmotic stress which would normally occur upon accumulation or storage of amino acids, organisms polymerize amino acids and store them as polypeptides. Amino acid + fad + h2o > -keto acid + nh3 + fadh2.
