Question

Which is not true about silk fibroin? Residues contain small sidechains (like alanine and glycine). O It is a form of tertiary structure O It contains parallel beta-sheets O The peptide strands are tightly packed to enhance tensile strength.

Answer 1

Answer: Silk fibroin is a protein produced by silk worms. The primary structure of this protein contain repeating units mainly made of alanine and glycine. It has simple tertiary structure where the heavy and light chains are linked by disulfide bonds. Silk fibroin contain high glycine content and hence the peptide is tightly packed, leading to increased tensile strength of the protein. Hence, options 1, 2 and 4 are true about silk fibroin and are incorrect answers.

The secondary structure of silk fibroin contains antiparallel beta-sheets but not parallel beta sheets. Hence, option 3 is not true about silk fibroin and is the correct answer.