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

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Solution

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

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