Digestion and Absorption GI Tract Flashcards
what are the layers solutes have to move through from lumen to blood
1) unstirred layer
2) glycocalyx
3) apical membrane
4) cytoplasm of cell
5) basolateral membrane
6) basement membrane
7) wall of blood capillary/ wall of lymphatic vessel
what does terminal ileum resection abolish?
bile salt and vit B12 absorption
what enzymes digest carbs?
1) salivary amylase
2) pancreatic amylase
3) brush border enterocytes (maltase, lactase, sucrase)
what test would you use to check for carb absorption and what do results mean
D-xylose test
less than 4 g in urine= problem with absorption
lactose intolerance
- brush border lactase enzyme deficient or absent
- causes osmotic diarrhea
what enzymes digest proteins?
1) pepsin (in stomach)- not essentail
2) trypsin/chymotrypsin (pancreas)
3) carboxypeptidase (pancreas)
4) aminopolypeptidase, dipeptidase, carboxypeptidase, endopeptidase (small intestine)
what activates pancreatic enzymes?
- trypsin
- enterokinase
what transporters, transport amino acids/peptides into epithelial cell of small intestine
1) Na cotransporter
2) H di or tripeptide cotransporter
* separate one for each a.a type
what transports amino acids from epithelial cell into blood?
- facilitated diffusion
- separate mech for each a.a type
- Na/K+ ATPase establishes gradient
what emulsfies fats into micelles?
bile salts and lecithin
what enzymes digests fats in the stomach?
-lingual and gastric lipase act on TAG
what enzymes digest fasts in small intestine?
- bile salts
- pancreatic enzymes
where does digestion of most fats take place?
small intestine
what are the pancreatic enzymes that digest fats in S.I?
- pancreatic lipase (activated by colipase)
- cholesterol ester hydrolase
- phospholipase A2
what transporters fats in circulation?
chylomicrons
*requires Apo B or wont get lipid absorption
