Lecture 68 Flashcards
(26 cards)
How do free fatty acids (such as those released from adipose stores during fasting) travel in the bloodstream?
Bound to Albumin
How many long chain FAs can bind to one albumin protein?
10
What happens to the majority of free FAs traveling in the bloodstream?
They are delivered to the liver where they are repackaged as triglyceride and incorporated into VLDL for delivery to other tissues.
What is the secondary structure of Apolipoproteins on the surface of lipoprotein particles?
Amphipathic alpha helices
Sizes of Lipoproteins:
Chylomicron: <0.95 g/ml VLDL: 0.95-1.01 g/ml IDL: 1.01-1.02 g/ml LDL: 1.02-1.06 g/ml HDL: 1.06-1.2 g/ml
Composition of Lipoproteins:
Chylomicron: 92% TG
VLDL: 50% TG
LDL: 36% CE and 10% Ch
HDL: 15% CE and 4% Ch
Chylomicrons (location, function, apolipoproteins)
Produced in intestinal enterocytes. Carrier of dietary fat (triglycerides) and cholesterol. Synthesized with ApoB-48; picks up ApoC-II and ApoE from HDL
VLDL (location, function, apolipoproteins)
Produced in the liver. Carrier of triglyceride and cholesterol to extra-hepatic tissues. Synthesized with ApoB-100; picks up ApoC-II and ApoE from HDL.
LDL (location, function, apolipoproteins)
Produced from VLDL after loss of triglyceride. Primary carrier of cholesterol and cholesterol esters to peripheral tissues or to liver for excretion.
HDL (location, function, apolipoprotines)
Active in reverse cholesterol transport. Produced in liver and intestine. Exchanges lipid and apolipoproteins between particles. Uses ApoA-I, ApoC-II and ApoE
What are the two major structural apolipoproteins and where are they found?
ApoB (VLDL, IDL, LDL, chylomicrons)
ApoA-I (HDL)
What are the variation in ApoB and where are they found?
ApoB-100: VLDL and LDL
ApoB-48: Chylomicrons
Which apolipoprotein activates lipoprotein lipase (LPL) on the surface of endothelial cells?
ApoC-II
How is the chylomicron remnant taken up by the liver?
via the ApoE receptor.
What happens to the glycerol released from the hydrolysis of triglycerides via LPL?
It is transported to the liver where it is
- used to make triglycerides for BLDL production
- Enters glycolytic or gluconeogenic pathways
Name 4 ways the liver can produce triglycerides
- de novo lipogenesis
2. repackaging of fatty acids that were taken up from adipose stores, chylomicron remnants or LDL
Describe the regulation of Lipoprotein Lipase (LPL)
During fasting:
- expression of LpL is down-regulated in adipose tissue
- expression of LpL is maintained in heart and other tissues
In the fed state:
-insulin and feeding stimulate LPL expression in adipose
Which apolipoprotein interacts with the LDL receptor?
ApoB-100
What happens to LDL after it is taken up by the LDL receptor?
It is delivered to the lysosome, where it is hydrolyzed to yield cholesterol, glycerol, fatty acids and AAs.
-LDL receptors are returned to the plasma membrane and re-used.
What is the leading cause of mortality worldwide?
Atherosclerosis of coronary and peripheral vasculature
Which enzyme exchanges cholesterol esters and triglycerides between HDL to LDL?
CETP (Cholesterol Ester Transfer Protein)
Which enzyme transfers cholesterol to the outer leaflet of the plasma membrane?
ATP-binding cassette protein (ABC-A1)
Which enzyme converts cholesterol to cholesterol esters in HDL? Why is this beneficial?
LCAT (Lecithin: cholesterol acyl transferase)
-Prevents reuptake of cholesterol by the cell and allows HDL to hold more cholesterol
What is Tangier disease?
Mutation in ABC-A1 transporter –> high intracellular cholesterol levels –> higher risk for coronary heart disease
