Digestion and absorption Flashcards
What is the site of B12 absorption?
Ileum
What are the cells that produce intrinsic factor?
Parietal cells of the stomach
Are oligosaccharide or polysaccharides absorbed directly?
No–digested to monosaccharides first
Where is the first primary site of polysaccharide digestion? What is the enzyme utilized here?
Lumen of the intestine
alpha-amylase
What stimulates the release of alpha-amylase? Where does the enzyme come from?
Ach and CCK
Pancreas
Where are the lactase, maltase, and isomaltase enzymes found?
On the brush border of the intestines
What are the glucose transporters utilized in the intestine?
Luminal side: SLGT1, GLUT5
Intracellular side: GLUT2
SGLT1 can move what across the membrane?
Na, Glu, Glc.
What is the substrate for GLUT5?
Fructose
Where does protein digestion begin? What is the enzyme utilized here? Where does this enzyme from from?
Stomach
Pepsin from chief cells
What is the function of gastrin?
Promotes acid secretion, and delays gastric emptying
What are the enzymes in the intestines that digest peptides? Where do these come from? What causes their release?
Trypsin–pancreas in response to CCK
Brush border peptidases
Are oligopeptide able to be absorbed, or do they need to be broken down fully to amino acids?
Can absorb oligopeptides
What is the transporter that can move small oligopeptides across the apical membrane? What is cotransported?
PEP1, uses H ions co transport
What is the transporter that can move amino acids across the apical membrane? What is cotransported?
B transporter
Na
Where do lipids begin to be digested? What are the enzymes utilized here?
Lumen of the stomach
Lingual lipase
Gastric lipase
Emulsification
What are the enzymes that digest lipids in the lumen of the duodenum?
Pancreatic lipase
Co-lipase
Emulsification
(Bile)
What inactivates gastric lipases?
pancreatic proteases and alkaline conditions
What is the primary site of lipid digestion?
Lumen of the duodenum
What is the cell types that responds to FAs in the duodenum? What does it release?
I cells, CCK
What is the function of colipase?
Regulatory protein that anchors lipase to fatty droplets—IT HAS NO ENZYMATIC ACTIVITY
What are the fat soluble vitamins? A defect in what leads to a deficiency?
A, D, E, K
Reduce bile synthesis or secretion
What is the transporter for cholesterol and FAs?
NPC1L1
What are chylomicrons?
MIxture of lipids in intestinal epithelial cells
What do chylomicrons combine with to be transported through the blood?
Lipoproteins
Where is the intrinsic factor receptor expressed?
Ileum
What is the protein that transports B12 in the body?
transcobalamin
Where is B12 stored? Secreted?
Liver and secreted in the bile
What happens to parietal cells as we age? Problem with this?
Less of them = less IF = less B12
What is the cause of pernicious anemia?
Several important pathologies are related to either an actual or a
functional vitamin B12 deficiency. Actual deficiency refers to a lack of vitamin B12 in
the diet whereas functional deficiency refers to an inability to absorb or otherwise
metabolize the vitamin.
What regulates the expression of the Ca transporter in the intestines?
Vit D
Lactose intolerance is due to what? What are the symptoms that this causes?
Lactase deficiency in the lumen of the intestines
Osmotic diarrhea–bacterial gas production
Lactose = what two monomers?
Glucose + galactose
Why does gastroparesis lead to poor glycemic control?
Irregular dumping of food into the intestines, causing inefficient absorption. This can change the amount of medication absorbed.
What is the role of folic acid?
Needed for DNA synthesis–thus will be upregulated if there is less B12, but no good
What transporter is utilized to transport glu, glc, and fructose across the basolateral cell membrane, into the interstitium?
GLUT-2
What is the transporter that absorbs cholesterol?
Neimann Pick C1-like1 (NPC1L1)
What is the importance of folic acid and B12? What is the primary symptom of a folate deficiency?
Used in DNA synthesis and cell division
Anemia d/t loss of RBC production
Colbalamin = ?
Vit B12
Why is ferric ion not absorbed from the intestines?
It precipitates out at pHs above 3
What is the vitamin that reduces Fe 3+ to Fe2+?
C
What is the protein carrier of Fe?
Transferrin
What is the transporter that absorbs Fe from the intestines?
divalent cation transporter 1 (DCT-1)
