PHY 503: CHO, PROTEIN, AND LIPID ABSORPTION: TEST
QUESTIONS WITH COMPLETE SOLUTIONS
What are M cells of Peyer's patches of the lymphoid follicles in the lamina propria? --
Answer ✔✔ package ingested whole proteins in clathrin-coated vesicles that are then
secreted across the basolateral membrane into the lamina propria, where
immunocompetent cells process the protein antigens to initiate immune responses
What are the three locations for digestion of proteins to amino acids? -- Answer ✔✔ 1)
GI lumen by way of pepsin in the stomach and endo/exopeptidases from the small
intestine
2) brush border to break down oligopeptides and dipeptides
3) in the cytoplasm of intestinal mucosal cells to break down remaining peptides into
individual amino acids
What is the function of trypsin? -- Answer ✔✔ activates other pancreatic protease
zymogens and trypsinogen proteins after being activated itself
What is enterokinase (enteropeptidase)? -- Answer ✔✔ a serine protease in the brush
border (mainly duodenum) that activates trypsinogen
, What do endopeptidases do? -- Answer ✔✔ cleave internal peptide bonds (60-70% of
luminal amino nitrogen is converted to oligopeptides this way)
What are the three endopeptidases and what do they do? -- Answer ✔✔ trypsin cleaves
at basic residues, chymotrypsin cleaves at aromatic residues, and elastase cleaves at
neutral residues
What do exopeptidases do? -- Answer ✔✔ cleave C-terminal peptide bonds, resulting in
individual amino acids (30-40% of ingested protein is cleaved this way)
What are the two exopeptidase and what do they do? -- Answer ✔✔ carboxypeptidase
A cleaves at aromatic and neutral aliphatic amino acids, and carboxypeptidase B cleaves
at basic amino acids
What is PepT1? -- Answer ✔✔ the oligopeptide transporter that allows for di- and
tripeptides to be taken up by enterocytes
What happens to di- and tripeptides after uptake by PepT1? -- Answer ✔✔ most are
hydrolyzed to single amino acids, but some show up in the portal vein (especially those
containing proline because they are more resistant to hydrolysis)
What drives the process of oligopeptide uptake? -- Answer ✔✔ a proton gradient that
is fueled by an Na+ gradient
QUESTIONS WITH COMPLETE SOLUTIONS
What are M cells of Peyer's patches of the lymphoid follicles in the lamina propria? --
Answer ✔✔ package ingested whole proteins in clathrin-coated vesicles that are then
secreted across the basolateral membrane into the lamina propria, where
immunocompetent cells process the protein antigens to initiate immune responses
What are the three locations for digestion of proteins to amino acids? -- Answer ✔✔ 1)
GI lumen by way of pepsin in the stomach and endo/exopeptidases from the small
intestine
2) brush border to break down oligopeptides and dipeptides
3) in the cytoplasm of intestinal mucosal cells to break down remaining peptides into
individual amino acids
What is the function of trypsin? -- Answer ✔✔ activates other pancreatic protease
zymogens and trypsinogen proteins after being activated itself
What is enterokinase (enteropeptidase)? -- Answer ✔✔ a serine protease in the brush
border (mainly duodenum) that activates trypsinogen
, What do endopeptidases do? -- Answer ✔✔ cleave internal peptide bonds (60-70% of
luminal amino nitrogen is converted to oligopeptides this way)
What are the three endopeptidases and what do they do? -- Answer ✔✔ trypsin cleaves
at basic residues, chymotrypsin cleaves at aromatic residues, and elastase cleaves at
neutral residues
What do exopeptidases do? -- Answer ✔✔ cleave C-terminal peptide bonds, resulting in
individual amino acids (30-40% of ingested protein is cleaved this way)
What are the two exopeptidase and what do they do? -- Answer ✔✔ carboxypeptidase
A cleaves at aromatic and neutral aliphatic amino acids, and carboxypeptidase B cleaves
at basic amino acids
What is PepT1? -- Answer ✔✔ the oligopeptide transporter that allows for di- and
tripeptides to be taken up by enterocytes
What happens to di- and tripeptides after uptake by PepT1? -- Answer ✔✔ most are
hydrolyzed to single amino acids, but some show up in the portal vein (especially those
containing proline because they are more resistant to hydrolysis)
What drives the process of oligopeptide uptake? -- Answer ✔✔ a proton gradient that
is fueled by an Na+ gradient
