Protein Digestion

Question 1

What are endopeptidases?

Answer 1

In the stomach, the protease enzyme hydrolyses internal bonds of a polypeptide chain producing shorter polypeptide chains to increase the surface area for faster and more efficient digestion. They have acidic optimum pH so don’t denature in stomach acid

Question 2

What are exopeptidases?

Answer 2

A protease enzyme in the pancreas (+exopeptidases) that hydrolyses terminal ends of polypeptide chains producing dipeptides and single amino acids. They are specific, one group complementary to the N (NH2) terminal end and another complementary to the C (COOH) terminal end

Question 3

What are dipeptidases?

Answer 3

Protease enzymes embedded in the cell surface membrane of the epithelial cells in small intestines which hydrolyses the single peptide bonds in the dipeptide to produce single amino acids, able to be absorbed via co-transport

Question 4

Process of amino acid absorption

Answer 4

1) Na+ ions are actively transported out of the epithelial cell into the blood by sodium-potassium pump
2) This creates a concentration gradient of Na+ between lumen of ileum and the epithelial cell
3) Na+ and amino acids enter by facilitated diffusion using a complementary co-transporter protein that has two binding sites, specific to each molecule
4) Na+ moves into cell down a concentration gradient
Amino acids move into cell against a concentration gradient
5) Amino acids move into blood by facilitated diffusion via a carrier protein