A protease cleaves a polypeptide that it recognizes at a pen

A protease cleaves a polypeptide that it recognizes at a pentapeptide segment. Assuming that a hydrogen bond is worth 2 kJ/mol, how much energy can it release by perfectly binding the backbone within the pentapeptide (that is, the four paptides within the five amino-acid segment)? Only count H-bonds for this problem and only one H-bond per C=O group.

A) 4 kJ/mol

B) 8 kJ/mol

C) 16kJ/mol

D) 24 kJ/mol

E) 32 kJ/mol

Solution

Answer: (C) 16kJ/mol

Considering the 4 peptides in the pentapeptide segment, hydrogen bond forms between the peptide bond nitrogen of one partner with the carboxy group of the other interacting partner and vice versa. Since hydrogen bonding is in 2:2 ratio and the number of C=0 to be considered is 4, the release of energy can be calculated as under:

Energy release = (4 * 2) * 2 kJ/mol = 16 kJ/mol