Textbook and Required Readings (Midterm) Flashcards
What are the three principal lipid components of bile?
Bile salts, pancreatic lipase, and sterols
What is bile?
The emulsifying fluid produced by the liver
Which fatty acids are resistant to hydrolysis by lipase?
FAs linked at the sn-2 position of MGs, PLs, and CEs
Under what form is cholesterol present in bile?
Unesterified form
How does phospholipase differ from pancreatic lipase?
Phospholipase cleaves FAs at the sn-2 position of PLs
Where is biliary cholesterol absorbed?
At a site more proximal than diet-derived cholesterol within the small intestine
What is the function of ABCG5 and ABCG8? Where are they found?
CH efflux proteins on the apical surface of the intestinal enterocyte
What do mutations in ABCG5 and ABCG8 cause?
- Phytosterolemia
- Hyperabsorption of plant sterols and premature atherosclerosis
What explains the low absorption efficiency of phytosterols?
1) Apical ABCG5 and ABCG8 transporters possess high affinity for phytosterols and preferentially excrete them back into the intestinal lumen
2) Inadequate esterification of phytosterols as ACAT dependent esterification of CH exceeds that of B-sitosterol
What are the functions of apolipoproteins?
- Increase particle solubility
- Increase recognition by enzymes and receptors located at the outer surface of lipoproteins
What are the hydrophilic components in lipoproteins?
Phospholipid polar head groups and cholesterol hydroxyl groups
What forms the core of lipoprotein molecules?
Hydrophobic cholesterol esters and triglycerides
What does the exogenous transport system transfer?
Transfers lipids of intestinal origin to peripheral and hepatic tissues
What is the relation between MTP and Apo-B?
MTP transfers lipids onto nascent Apo-B particles to create chylomicrons
What kind of lipids do not require chylomicron incorporation?
FAs less than 14 carbons in length undergo direct internal transport via the portal circulation (direct delivery to the liver)
What do chylomicron TG-depleted remnant particles take up? Where are they taken?
- Take up CE from HDLs
- Rapidly taken up by the liver
What is the function of ABCA1?
Mediate the efflux of cellular cholesterol and phospholipids to lipid-poor HDL
Where is Apo E synthesized? Where is it present?
- In the liver
- On all forms of lipoproteins
Why is Apo E important?
In the hepatic clearance of TG-depleted chylomicron remnants
Where is LDL cleared from the plasma?
- Liver
- Adipocytes
- Smooth muscle cells
- Fibroblasts
- All contain the LDLR
As HDL becomes enriched with CE, ______ and ______ are picked up from other proteins to form spherical HDL.
Apo-C-II and Apo-C-III
What does CETP exchange?
- CE from HDL2 to VLDL and CM
- TG from VLDL and CM to HDL2
As a result of CETP’s action, what does HDL2 convert to?
Reconverts to HDL3
What is the consequence of manipulating ER calcium?
- Causes the re-distribution of a portion of intracellular UC to a pool that is NOT available to the SCAP-SREBP complex
- Not directly accessible to the components of the cholesterol-sensing mechanism
What is the consequence of a reduction in ER luminal calcium?
- Increased abundance of nSREBP
- Increase in LDLR, FASN, HMGR
What kind of nuclear receptors are steroid receptors?
Homodimers
What kind of nuclear receptors are RXR receptors?
Heterodimer