Which amino acid required in infants and not in adults?

Ans. is 'a' i.e., Histidine* Histidine and Arginine are partially or semiessential aminoacids. They are synthesized by metabolic pathways but the rate of synthesis is low, that the endogenous synthesis is not sufficient to meet the requirements during periods of increased demand like during growth* Glycine is a non-essential aminoacid as it can be synthesized from serine, threonine and reversal of glycine cleavage system* Isoleucine and Valine are essential aminoacids.