Tyrosine enters at which level in citric acid cycle-

Ans. is 'b' i.e., Fumarate o All major members of the citric acid cycle from citrate to oxaloacetate are glucogenic and therefore, are involved in gluconeogenesis. Some glucogenic aminoacids enters the TCA cycle after transamination e.g.:a) Histidine, proline, glutamine and arginine are converted to glutamate which is then transaminated to a- ketoglutarate.b) Isoleucine, methionine and valine enter by conversion into succinyl CoA. Propionate (a short chain fatty acid)also enter at this level.c) Tyrosine, and phenylalanine enter by conversion into fumarate.d) Tryptophan is converted to alanine which is then transaminated to pyruvate.e) Hydroxyproline, serine, cysteine, threonine and glycine enter by conversion into pyruvate.