LE 4: Nitrogen Metabolism

mouth

• no digestion

• mechanical breaking of food into smaller particles

STOMACH

entry of dietary proteins stimulates the gastric mucosa to secrete the hormone gastrin that stimulates the secretion of:

• HCl – denatures proteins

• pepsinogen – zymogen of pepsin; activated by HCl

gastrin

hormone that stimulates the secretion of:

• HCl – denatures proteins

• pepsinogen – zymogen of pepsin; activated by HCl

HCl

strong acid that denatures proteins in the stomach

pepsinogen

• stomach enzyme
  - zymogen of pepsin; activated by HCl

SMALL INTESTINE

entry of chyme into the duodenum

stimulates the secretion of

• secretin – triggers the release of HCO3 in the small intestine making the pH neutral

• cholecystokinin – stimulates the secretion of different proteases by thepancreas which are active at pH 7-8

proteases

different ____ act on oligopeptides to yield amino acids

• aa: trypsin, chymotrypsin, thermolysin, carboxypeptidase, aminopeptidase

epithelial cells

free amino acids are then transported to _____in the lining of small intestine where they can enter the bloodstream an be transported to the liver

ACUTE PANCREATITIS

occurs when zymogens are prematurely

activated in the pancreas and they target the

pancreas itself

protein turnover

• the process of degradation and re-synthesis of proteins in the body

• constantly occurring in the cell because proteins have different half

lives

• non-functional or misfolded proteins are targeted for degradation in

order to use the amino acid products for synthesis of other proteins