Question

A decapeptide $\left(Mol.wt.796\right)$ on complete hydrolysis gives glycine $\left(Mol.wt.75\right)$, alanine and phenylalanine. Glycine contributes $47.0\%$ to the total weight of the hydrolysed products. Calculate the number of glycine units present in the decapeptide.

Answer 1

Answer: 6

Molecular weight of decapeptide $=796g/mol$
Total bonds to be hydrolysed $=\left(10-1\right)=9$ per molecule
Total weight of $H_{2}O$ added $=9\times 18=162g/mol$
Total weight of hydrolysis products $=796+162=958g$
Total weight $\%$ of glycine (given) $=47\%$
Total weight of glycine in product
$=\frac{958\times 47}{100}g=450g$
Molecular weight of glycine $=75g/mol$
Number of glycine molecules $=\frac{450}{75}=6$