RRB Paramedical Staff Nurse Model Paper 2

An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized de novo(from scratch) by the organism, and thus must be supplied in its diet. The nine amino acids humans cannot synthesize are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.