Lecture #23 - Lipid stuff Flashcards
What is the backbone of triaclyglycerol?
What is cholesterol ester the procures to (3)
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Bile Acids (salts)
- Made from ____
- Synthesised in ____ and stored in ___ _____ as _____
- Secreted into small intestine in response to _______
So what do bile salts do to triacyleglyerols?
- They are powerful _____ with what surfaces?
- What do they form with triacylglycerols to increase the surface area of lipid at interface with the aq environment where enzymes can act on them
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How do bile salts and cholesterol differ/how are they similar and how does that allow bile salts to associate with lipids?
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What’re gall stones? What can they lead to?
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So lipid are emulsified by bile salts to form micelles. What does pancreatic lipase do once the micelle is formed?
Where are the hydrolysed lipids taken up?
Where does pancreatic lipase hydrolyse the fatty acids and leaves what behind? What else is in the micelles and what breaks those down? Then what forms (smaller m___) and then they’re absorbed across what?
It binds to lipid/aq interface of micelle and hydrolyses TAGs within them
Apart from the activity of a gastric lipase, which aids the digestion of milk lipids in the newborn, lipid digestion does not occur to any extent until the small intestine. Here, triacylglycerol molecules are cleaved by pancreatic lipase, which preferentially hydrolyses the fatty acids from positions 1 and 3 of the glycerol backbone. Also contained in the pancreatic juice are cholesterolesterase and phospholipase enzymes which hydrolyse cholesterol esters and phospholipids respectively, that are also contained in the micelles.
Once hydrolysed, the lipid components (free fatty acids, monoacylglycerol and cholesterol) are incorporated into smaller micelles, again aided by the bile acids. These micelles are then absorbed across the brush border of intestinal mucosal cells by the action of various fatty acid and cholesterol transporters.
So lipid are emulsified by bile salts to form micelles. What does pancreatic lipase do once the micelle is formed?
Where are the hydrolysed lipids taken up?
Where does pancreatic lipase hydrolyse the fatty acids and leaves what behind? What else is in the micelles and what breaks those down? Then what forms (smaller m___) and then they’re absorbed across what?
It binds to lipid/aq interface of micelle and hydrolyses TAGs within them
Apart from the activity of a gastric lipase, which aids the digestion of milk lipids in the newborn, lipid digestion does not occur to any extent until the small intestine. Here, triacylglycerol molecules are cleaved by pancreatic lipase, which preferentially hydrolyses the fatty acids from positions 1 and 3 of the glycerol backbone. Also contained in the pancreatic juice are cholesterolesterase and phospholipase enzymes which hydrolyse cholesterol esters and phospholipids respectively, that are also contained in the micelles.
Once hydrolysed, the lipid components (free fatty acids, monoacylglycerol and cholesterol) are incorporated into smaller micelles, again aided by the bile acids. These micelles are then absorbed across the brush border of intestinal mucosal cells by the action of various fatty acid and cholesterol transporters.
Fat malabsorption:
- Leads to what?
- Caused by what? Examples? (4 examples)
Examples: pancreatitis, gall bladder or liver disease and untreated CF
Xenical: potent i____ of pancreatic lipase
- what does it reduce?
- how does it work?
- additional benefit of it is? (to do with feces)
-amount of fat ingested
So what happens to absorbed FA and MAGs in the intestinal cell? What enzyme resynthesises? What if mutation in this enzyme?
Idk the name wither but I think it’s like CoA?
What three things form chylomicrons (it’s a type of lipoprotein) ? And where does this go? Blood? No? Then what?
On the reaction scheme it’s written that TAG and apoproteins and other lipids form it
What’s the delivery system of lipids?
What are the four classes? How are they named (two names)
Lipoproteins
Lipoproteins
- “___” lipids for transport in what to what?
- Provide a delivery system for shifting?
- Apoproteins have important functions - name three and their associated apoprotein)
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What are the two lipid transport pathways? Describe each and also describe the chylomicron assembly
About 50% of the VLDL remnants go back into the liver (using the ApoE receptor), where they’re broken down to glycerol backbones and individual free fatty acids. These are then used to build up TAGs again. These TAGs can be packaged into a liporpotein and put out into the blood stream again. The type of lipoprotein will depend on its protein and TAG proportion. When lipoproteins are circulating in the blood stream, lipoprotein lipase can act on them, releasing free fatty acids (and the glycerol back bone), which can be taken up by next door fat (adipose) or muscle cells (and used straight away or stored as TAGs to be used later). The free fatty acids can also bind to the transport protein albumin and be taken to other cells further away when/if needed. The glycerol, being soluble, don’t beed a transport protein. Once at the other location (a skeletal or adipose cell further away), the free fatty acids and glycerol back bone is used to resynthesise the TAG which is stored until it’s needed. The other 50% of the VLDL remnants will be further acted on by hepatic lipase. Hepatic lipase is made in the liver but acts in the blood. It breaks most of the remaining TAGs down, which are absorbed or transported as described above. As the TAG content decreases even further, the TAG vs protein proportions have changed so much that the resulting lipoprotein is now classified as LDL. LDL has a high proportion of cholestrol = bad. There is an LDL/ApoB100 receptor on the liver so the “bad content” of the LDL can be taken to the liver where is can be kept safely until it’s removed (poo it out). However, non-hepatocytes also have the LDL receptor, so the contents of LDLs can be taken up by other tissues as well, where it may be damaging.
Lipoprotein lipase
- Where is the enzyme found?
- What does it hydrolyse and into what?
- Where are the highest activities?
- Activated by what?
- Defects (by mutation) in either apoCII or lipoprotein lipase leads to what?
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