Biomolecules and Chemistry in Everyday Life - Result Question 33

34. A decapeptide (Molecular weight $796$) on complete hydrolysis gives glycine (Molecular weight $75$), 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

(2011)

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Answer:

Correct Answer: 34. $(6)$

Solution:

  1. A decapeptide has nine peptide (amide) linkage as

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Therefore, on hydrolysis, it will absorb nine water molecules.

Hence, total mass of hydrolysis product $=796+18 \times 9=958$

$\Rightarrow$ mass of glycine in hydrolysis product $=\dfrac{958 \times 47}{100}=450$

$\Rightarrow$ number of glycine molecule in one

molecule of decapeptide $=\dfrac{450}{75}=6$