Protein Digestion

Question 1

What are proteins hydrolysed by?

Answer 1

A group of peptidase enzymes
1. Endopeptidases
2. Exopeptidases
3. Dipeptidases

Question 2

What do endopeptidases do?
Give examples

Answer 2

• hydrolyse peptide bonds in the central region of a protein molecules forming a series of peptide molecules

eg
1. trypsin and chymotrypsin (secreted by pancreas and small intestine)
2. pepsin (produced by cells lining the stomach, only works in acidic conditions, hence the release of HCL acid in the stomach)

Question 3

What do exopeptidases do?

Answer 3

• hydrolyse peptide bonds at the ends of a peptide molecule formed by endopeptidases and release dipeptides and amino acids
• as a result of endopeptidases, exopeptidases will have more ends to hydrolyse peptide bonds and hence protein digestion will be faster

eg aminopeptidases and carboxypeptidases

Question 4

What do dipeptidases do?

Answer 4

• complete protein digestion by hydrolysing the peptide bonds in a dipeptide to release amino acids
• they are membrane bound so part of the cell surface membrane of the epithelial cells lining the ileum