Biochemistry - Fatty Acid Transport and Catabolism Flashcards
In which organs are HDL synthesized?
Liver and intestine - released as a “nascent HDL disc”
Which apoprotein is present on VLDL?
B100
What is the composition of TAGs vs. CEs in VLDL?
TAGs»_space; CEs
What does HDL transfer to VLDL upon entering the bloodstream?
Apo CII and E
What receptor does VLDL bind to on cells that need FFAs?
LPL
When a VLDL transitions to become an IDL, what two things happen?
- TAGs = CEs
2. Loss of Apo CII
After VLDL becomes an IDL, what two things can happen to it in a liver cell?
- If body cells have enough FAs, IDL will bind to LDL-R, get entocytosed, and reused for synthesis or more VLDLs.
- Bind to hepatocyte TAG lipase (HTGL) receptor, TAGs go into liver cell for hydrolysis, IDL loses Apo-E and becomes a LDL.
What is the defect in people with familial hypercholesterolemia?
Defective or too few LDL-receptors - unable to take in cholesterol from LDL. LDL gets oxidized, invades blood vessel endothelium.
What macrophage receptors bind oxidized LDL in the intima of blood vessels? What does this result in?
Scavenger receptors bind, macrophage eats LDL, which eventually results in a foam cell. Foam cells stimulate metalloproteases for angiogenesis and they also release growth factors and cytokines.
What HDL apoprotein activates lecitin cholesterol acyl transferase (LCAT)?
Apo A-I
What does LCAT do?
Allows HDL to take cholesterol from cells that have too much:
Transfers a FA from lecithin to the excess cholesterol to make a cholesterol ester, which is then transferred to HDL, which travels back to the liver for endocytosis and degradation.
Which enzyme is used to transfer CEs from HDL to IDL and TAGs from IDL to HDL? Why is this done?
Cholesterol ester transfer protein. It generates LDL that can deliver cholesterol to cells that need it.
What is the half life of VLDL?
~3 hours
What is considered a normal cholesterol level?
~200 mg/dl
What are normal HDL and LDL cholesterol levels?
HDL: 40 mg/dl, LDL: 120 mg/dl
