Question

Molecular mass of the glycine is 75 g/mol, methionine is 149 g/mol, alanine is 89 g/mol, valine is 117 g/mol and phenylalanine is 165 g/mol.

Then what would be the molecular mass of protein with sequence
Gly – Ala – Phe – Val – Met – Gly

• A. 595 g/mol
• B. 523 g/mol
• C. 670 g/mol
• D. 580 g/mol

Answer 1

The correct option is D 580 g/mol

This protein has 5 peptide bonds, and during formation of each peptide bond 1 molecule of water having molecular mass of 18 g/mol is removed. So molecular mass of this protein would be

= (2 × Gly + Ala + Phe + Val + Met) – (5 × Water)
= (2 × 75 + 89 + 165 + 117 + 149) - (5 × 18)
= 670 - 90
= 580 g/mol