Question

The synthesis of proteins requires 20 standard amino acids in the living systems. However, some organisms use selenocysteine as an additional amino acid for synthesizing proteins. Selenocysteine is biosynthesized from

• A. Cysteine
• B. Serine
• C. Threonine
• D. Proline

Answer 1

The correct option is A Cysteine

Selenocysteine is also known as the 21st amino acid, which is unique among the proteinogenic amino acids. This is a naturally occurring amino acid in eukaryotes and prokaryotes.

Selenocysteine is biosynthesized from the amino acid cysteine. where the sulfide is replaced by the selenium.

So the answer is 'Cysteine'.