A decapeptide(M. mass = 796) on complete hydrolysis gives glycine, alanine and phenylaline. Glycine contributes 47% to the total mass of hydrolysed products. Calculate the number of glycine units present in the decapeptide.

Explanation

Molecular mass of decapeptide = 796
Molar mass of glycine `(H_(2) NCH_(2)COOH) = 75`
The number of `H_(2)O` molecules that will be required for the hydrolysis of the decapeptide must be 9.
Decapeptide `+9H_(2)O rarr` Glycine + Alanine + Phenylalanine
Now, total mass of all the amino acids obtained after addition of 9 molecules of `H_(2)O 796 + (9 xx 18) = 958`
`:.` Total mass of glycine in the hydrolysed products `= (958 xx 37)/(100) ~~ 450`
But molecular mass of glycine = 75
`:.` No. of glycine units in the decapeptide `= (450)/(75) = 6`