<prompt> Which of the following is a Semi-essential aminoacid-TyrosineHistidineAlanineIsoleucine  <response>: Ans. is b i.e., Histidine Histidine is a semiessential aminoacid, as this aminoacid can be synthesized by metabolic pathways in human. But the synthetic rate is not sufficient enough to meet the increased demands during growth spurts. Tyrosine and Alanine are non essential aminoacids Isoleucine is an essential aminoacid 