A tetrapeptide has -COOH group on alanine. This produces glycine (Gly), Valine (Val), Phenyl alanine (Phe) and Alanine (Ala) on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with -NH 2 group attached to a chiral center is

Step-by-step solution

Following combinations are possible for tetrapeptide: Val - Phe - Gly - Ala Val - Gly - Phe - Ala Phe - Gly - Val - Gly Phe - Val - Gly - Ala In all above sequences, C-terminal is alanine. Glycine is optically inactive amino acid, it can not be N-terminal. Hence, only above combinations are possible.