Protein digestion

Question 1

Describe how proteins are digested in the human gut.

Answer 1

Hydrolysis of peptide bonds;

2. Endopeptidases break polypeptides into smaller peptide chains;
3. Exopeptidases remove terminal amino acids;
4. Dipeptidases hydrolyse / break down dipeptides into amino acids.

Question 2

Describe the structure of proteins.

Answer 2

Polymer of amino acids;

2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding of polypeptide chain due to hydrogen bonding;

Accept alpha helix / pleated sheet

6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
7. Quaternary structure is two or more polypeptide chains

Question 3

Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own.

Answer 3

Endopeptidases hydrolyse internal (peptide bonds)

OR

Exopeptidases remove amino acids/hydrolyse (bonds) at end(s);

Accept: break for hydrolyse.

Accept: endopeptidases break (proteins) into shorter chains.

2. More ends or increase in surface area (for exopeptidases);

Question 4

Trypsin is a protease. It is produced in an inactive form inside some of the cells of the pancreas.

(a) Name the part of a pancreatic cell that produces the inactive form of trypsin.

Answer 4

Ribosome/rough endoplasmic reticulum;