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17 Cards in this Set
- Front
- Back
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Where did I pull this crap from?
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Costanzo's Phys 4ed, pg 365 - 369
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What is the process by which B12 is absorbed?
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1. B12 is released from foods by pepsin in the stomach
2. free B12 binds to R proteins from salivary juices 3. in the duodenum, pancreatic proteases move B12 from R proteins over to intrinsic factor 4. B12:IF is safe from proteases and moves into ileum 5. B12:IF moves into the lleal cells by receptor mediated endocytosis 6. B12 binds transcobalamin II and appears in the blood as B12:transcobalamin II |
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What's so great about intrinsic factor?
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comes from the parietal cells and allows B12 to be taken into the intestinal epithelium. if IF is not around, you need a boat load (> 1mg/day) of B12 to avoid pernicious anemia.
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What happens if there is not enough intrinsic factor or if it's not absorbed properly?
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no IF => pernicious anemia.
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What 3 types of lipids are digested?
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3 kinds of lipids (triglycerides, cholesterol esters, phospholipids) go down in similar ways
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What's the path of triglyceride digestion?
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1. lingual, gastric lipases get the show started
2. CCK slows gastric emptying when lipids hit the stomach to allow enough time to process 3. bile salts in the small bowel emulsify the lipids 4. pancreatic lipase does most of the triglyceride breakdown work, but the bile salts inactivate it. colipase (secreted as procolipase and activated by trypsin) displaces bile salts and allows pancreatic lipase to do the deed 5. now these suckas are broken down into monoglycerides and 2 FAs |
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What's the path of fat absorption?
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1. all the products of fat digestion (monoglyceride, FAs, cholesterol, lysolecithin) are emulsified by bile salts into micelles
2. micelles diffuse into brush-border of intestinal epithelial cells and diffuse down concentration gradient 3. sER stitches lipid products back together by reesterification 4. constituents are packaged into chylomicrons, where Chol E and TG sit in the middle of the cell and are surrounded by Apo B and PLs 5. chylomicrons get packed into vesicles by Golgi and exocytosis ensues. 6. welcome to the lymphatics |
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What's the difference between micelles, pre-chylomicrons, chylomicrons, and VLDLs?
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Yeah, ok...
1. micelles - bile salt emulsified fat digested constituents made to allow absorption across the apical intestinal epithelium 2. pre-chylomicrons - the chylomicrons before they are packaged by the Golgi and released into lymph 3. chylomicrons - reassembled (reesterified) fats with a TG/Chol E core and a PL/Apo B cover that get assembled in the sER, packaged by the Golgi and properly travel into the lymphatics 4. VLDLs - similar to chylomicrons, but made when fat content is reduced and they are more dense |
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What's the path of cholesterol ester digestion?
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cholesterol ester hydrolase breaks down cholesterol esters into cholesterol and FAs
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What's the path of phospholipid digestion?
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phospholipase A2 is secreted as a proenzyme and is activated by trypsin. it breaks down phospholipids into lysolecithin and FAs
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What's abetalipoproteinemia?
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Apoproteins are those things that comprise about 10% of the (pre-)chylomicron surface along with PLs. if you can't make Apo B, then you can't absorb chylomicrons and you can't absorb dietary lipids
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What's the general causes of lipid malabsorption?
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1. pancreatic insufficiency
2. \/ duodenal pH causing denaturing of pancreatic juices like in ZES 3. bile salt deficiency 4. bacterial overgrowh => \/ pH \/ intestinal cells (like tropical sprue or celiac dz) 5. abetalipoproteinemia |
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What two mechanisms allow bile acid absorption?
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1. for conjugated -OH'ed bile acids - secondary active transport by Na gradient
2. for unconjugated bile acids - simple diffusion both occur in the terminal ileum to be recycled |
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How do bile acids work?
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Bile salts are bile acids compounded with a cation, usually sodium. So bile acids work the same way... they're basically the same thing.
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This may be too detailed, but what are these: MVM-FABP, I-FABP, L-FABP, SCP-1 and -2?
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1. MVM-FABP - protein on plasma membraen using energy from Na gradient to move long-chain FAs and lysoPLs across the brush border
2. I-FABP - binds LCFAs 3. L-FABP - binds monoglycerides, lysophosphatides, cholesterold, and LCFAs 4. SCP-1, -2 - bind cholesterol and other sterols |
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What does glycerol ester hydrolase do to TGs?
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breaks 'em down into 2 FAs and a monoglyceride. i was just a little more general with the "lingual, gastric lipase" term used earlier.
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What's the critical micelle concentration?
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the amount of bile acids needed at minimal concentration to form micelles in the duodenum
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