Module 6: Amino Acids and Proteins Obj. 4

Question 1

process of protein digestion

Answer 1

proteins broken down by hydrolytic enzymes in digestive juices into AMINO ACIDS before they can be absorbed across intestinal mucosal cells into the renal-portal circulation

Question 2

source and action of gastrin

Answer 2

proteins from ingested food stimulate secretion of gastrin by astral mucosal cells and by J-cells of pancreatic islet of Langerhans

Gastrin induces release of Hal, secretion of pepsinogen and pancreatic fluid

Question 3

source and action of HCl

Answer 3

Parietal cells of stomach
Causes protein denaturation, conversion of pepsinogen to pepsin, provides acidic environment for pepsin action to destroy bacteria

Question 4

source and action of pepsinogen

Answer 4

secreted from chief cells of stomach

Question 5

endopeptidases

Answer 5

pepsin, trypsin, chymotrypsin

act on large polypeptides after action of Hal
Catalyze hydrolysis of peptide bonds around the middle portion of the chains

Action continues until peptides formed are too small for further action

Question 6

exopeptidases

Answer 6

catalyze hydrolysis of the terminal peptide bonds in small peptides
Carboxypeptidases (if they act at the carboxyl end of the peptide)
Amino peptidases (if they act at amino end)

Action results in release of individual amino acids by action of the enzyme dipeptidase