A protein 'X' with molecular weight of 70,000 u, on hydrolysis gives amino acids. One of these amino acid is

A protein is a long‐chain polypeptide. Each peptide bond is formed by the condensation of the α-carboxyl group of one α-amino acid with the α-amino group of the next. Accordingly, when any protein is hydrolysed—whether by boiling with dilute mineral acid, by alkali or by proteolytic enzymes—the only small molecules that appear in the reaction mixture are α-amino acids (or their side-chain derivatives).

An α-amino acid has the general skeleton
$$HOOC\!-\!CH(NH_2)\!-\!R$$
i.e. both the amino (-NH2) and carboxyl (-COOH) groups are bonded to the same (α) carbon atom.

To answer the question, we scan the four structures given in the options and look for the one that possesses:

(i) a ‑COOH group,

(ii) a ‑NH2 group,

(iii) both groups attached to the same carbon.

Among the four alternatives, only the compound shown in Option B satisfies all three conditions, making it a genuine α-amino acid. The remaining choices either lack one of the two functional groups or have them bonded to different carbon atoms, so they cannot arise from protein hydrolysis.

Therefore, one of the amino acids obtained from the hydrolysis of protein ‘X’ is the compound in Option B.

Final answer: Option B which is: the α-amino acid depicted in the option.