MP - Hu - 2/23 - Intestinal Transport II Flashcards
Pepsin from the stomach and the five pancreatic proteases hydrolyze proteins (both dietary and endogenous) to: ___, or ___
single amino acids, AA
oligopeptides, (AA)n
Where do pepsin from the stomach and the five pancreatic proteases hydrolyze proteins?
Lumen of stomach or small intestine
What do various peptidases at the brush borders of enterocytes progressively do?
Hydrolyze oligopeptides to amino acids
The enterocyte directly absorbs some of the small oligopeptides through the action of the ___ across the apical membrane
H+/oligopeptide cotransporter (PepT1)
What happens to small peptides once in the enterocyte?
They are digested to amino acids by peptidases in the cytoplasm of the enterocyte and then moved out of the cell across the basolateral membrane by Na+-independent amino acid transporters
Amino acid transport is __1__ with __2__ preferentially absorbed
- stereospecific
2. L-isomers (over D-isomers)
T/F: Most carriers transport amino acids against concentration gradient
True
T/F: The mechanism of transport for sugars—facilitated diffusion or sodium-coupled cotransport–is kinetically the same as for the transport of amino acids
True
___ is the Na+-coupled transporter that mediates the uptake of glucose or galactose from the lumen of the small intestine into the enterocyte
SGLT1
___ mediates the facilitated diffusion of fructose into the enterocyte
GLUT5
Once the monosaccharides are inside the enterocyte, ___ mediates their efflux across the basolateral membrane into the interstitial space
GLUT2
T/F Lipase is water soluble like all luminal enzymes of digestion
True
T/F Colipase anchors lipase to micelles and provides access to neutral triglycerides inside micelles
True
T/F Pancreatic lipase hydrolyzes only at 1 and 3 position of triglycerides
True
What are micelles?
Aggregates of amphipathic molecules including:
Long chain fatty acids
Fat soluble vitamines (A, D, E, K) Cholesterol
Monoglycerides
Phospholipids
Bile salts