lecture 11 - GI absorption Flashcards
What is the rate of GI absorption directly porportional to?
Surface area of the gut lumen
What is GI absorption?
Net passage of substance from lumen of gut, across epithelium, and into the interstitial fluid
Which motility pattern aids in GI absorption?
Segmentation
What are the 5 key factors that affect absorption in the GI tract?
Surface area, motility, adequate digestion, penetration, removal of substances from interstitial space
Why is it important for GI absorption to remove substances from the interstitial space?
Ensures a concentration gradient can be maintained so that substances can be moved from epithelial cells
What substances are absorbed in the stomach?
Ethanol, aspirin - nil nutritional absorption
What substances are absorbed in the colon?
Water, sodium, vitamins, short chain fatty acids, etc.
Is GI uptake of sodium selective or non-selective?
Non-selective, all sodium is taken up (if transporters are available) and kidneys maintain the balance in the flood by removing excess
Where are carbohydrates absorbed in the GI tract?
Duodenum, jejunum of the small intestine
What enzyme breaks polysaccharides into disaccharides?
Amylase
What converts disaccharides to monosaccharides in the GI tract?
Enzymes on the brush border of the small intestine
What transport mechanism is mostly used to absorb carbohydrates in the GI tract?
Na co-transport
What enzymes are used to to break down proteins in the GI tract?
Proteases (pepsin, trypsin, chymotrypsin), peptidases
What is the function of brush-border peptidases in the small intestine?
Break peptides down into single amino acid for absorption
How are amino acids absorbed in the GI tract?
Via co-transport with sodium
