Question

Sulphur containing amino acid is
(a) Methionine
(b) Cystine
(c) Cysteine
(d) All of the above

Answer 1

Hint: Sulphur containing amino acids play a role as a fundamental metabolite. One of the sulfur-containing amino acids is a propanoic acid with an amino group at position 2 and a sulfanyl group at position 3. One amino acid which is a precursor for all other amino acids is found in meat, fish, and dairy products.

Complete step by step answer:
The building blocks that our bodies use to make proteins are amino acids. To form a protein, the amino acids are linked together by peptide bonds.
Methionine is the sulfur-containing amino acid. Their molecular formula is ${ C }_{ 5 }{ H }_{ 11 }{ NO }_{ 2 }S$. It helps in the initiation of protein synthesis.
Cystine is a dimer that is obtained by oxidation of cysteine. Their molecular formula is ${ C }_{ 6 }{ H }_{ 12 }{ { N }_{ 2 }O }_{ 4 }{ S }_{ 2 }$​.                
Cysteine is a semi-essential protein. Serine acts as a precursor and the sulfur is derived from methionine. The molecular formula is ${ C }_{ 3 }{ H }_{ 7 }{ { N }O }_{ 2 }{ S }$.
So, the correct answer is, ‘All of the above’.

Additional information:
The amino acids (cysteine and methionine) containing sulfur are commonly known to be nonpolar and hydrophobic. In fact, one of the most hydrophobic amino acids is methionine, which is almost always found within proteins. On the other hand, cysteine does ionize to yield the anion of thiolate. Even so, finding cysteine on the surface of a protein is rare.

Note: In 1921, methionine was isolated by John Howard Mueller. It comprises an alpha-amino group, a carboxyl group, and an S-methyl thioether side chain. It is classified as a nonpolar and aliphatic amino acid. In 1810, Cystine was found by William Hyde Wollaston. Human hair and skin have a mass of around 10-14 percent cystine. In order to produce wool, cysteine is needed by sheep.