In liver ammonia is formed from which amino acid?
ANSWER: (B) GlutamineREF: Harper 29th Ed Page 521, 529, 530, Lehninger Biochemistry 4th ed page 523, 538,539Both Glutamine and Alanine (If provided in the options) should be the answer but since alanine is not in options Glutamine is the best possible answer. If Alanine is also provided in the options separately then also Glutamine is the best answer, since it is found in most tissue however glucose-alanine cycle/ cori cycle is for skeletal muscles only.Two mechanisms are available in humans for the transport of ammonia from the peripheral tissues to the liver for its ultimate conversion to urea.1. The first, found in most tissues, uses glutamine synthetase to combine ammonia with glutamate to form glutamine--a nontoxic transport form of ammonia. The glutamine is transported in the blood to the liver where it is cleaved by glutaminase to produce glutamate and free ammonia.2. The second transport mechanism, used primarily by muscle. involves transamination of pyruvate {the end product of aerobic glycolysis) to form alanine. Alanine is transported by the blood to the liver, where it is converted to pyruvate, again by transamination. In the liver, the pathway of gluconeogenesis can use the pyruvate to synthesize glucose, which can enter the blood and be used by muscle--a pathway called the glucose-alanine cycle or Cori cycle or Lactic acid cycleThe Glucose/ alanine cycle
Glycine
Glutamine
Isoleucine
Proline
Amino Acid Metabolism