Biochemistry

Oxalacetic acid can add ammonia to itself and again turn into aspartic acid or, undergoing decarboxylation, into pyruvic acid, and then into coenzyme A, which is used in various biosynthesis reactions or oxidized to CO 2 and H 2 O. The resulting arginine under the action of arginase is hydrolytically break down into ornithine and urea. Arginine nh 2 C=NH NHj CH, /NH 2 + H 2 O, arginase ch , ------------------- ; ------------ *■ + 6=0 x nh 2 CH CH 2 1 1 Сң H,N — CH — COOH 1 1 . COOH Ornithine Urea Released ornithine may again react with a new carbomoylphosphate molecule and the process will repeat. It is estimated that in a state of nitrogen equilibrium, the adult body consumes and accordingly releases 15 g of nitrogen; urea accounts is about 85% from the nitrogen excreted in urine, creatinine - 5, ammonium salts - 3, uric acid - 1, and its other forms - 6. 8.6 CHROMOPROTEIN METABOLISM Consider a chromoprotein metabolism on the example of hemoglobin metabolism, which is part of red blood cells. Red blood cells arise from bone marrow reticular cells. Each red blood cell has its own life cycle in the body, which ends with its destruction. Destroyed red blood cells number corresponds to the number of newly formed one and, thus, their mass in the blood does not change. 0.85% of the total mass of red blood cells is destroyed daily. The life spans of red blood cells are not the same in different animal species. In humans, this period is 126 days, in dogs - 107 days, in cats and rabbits - 68 days. 176