Lipoprotein Transport Flashcards
Describe the transport of free fatty acids in blood.
Free fatty acids are transported in blood complexed to albumin (noncovalent)
How are TAGs and cholesteryl esters transported in blood
TAGs and cholesteryl esters are transported inside of the lipoproteins
How are dietary lipid-soluble vitamins and dietary essential fatty acids in TAGs transported to the liver?
Dietary lipid-soluble vitamins and dietary essential fatty acids in TAGs reach the
liver via chylomicron remnants.
Dietary essential fatty acids are also stored after a meal in TAGs in fat cells and
can reach the liver during fasting as free fatty acids via transport by albumin
Which lipoprotein has the highest percentage of proteins?
HDL has the highest percentage of proteins due to apolipoproteins.
Which lipoprotein has the highest percentage of cholesterol plus cholesteryl esters?
LDL has the highest percentage of cholesterol plus cholesteryl esters
Which two lipoproteins are TAG-rich?
Chylomicrons and VLDL are TAG-rich lipoproteins
Which lipoprotein contains dietary lipids?
Chylomicrons are the lipoproteins that contain dietary lipids, mostly TAGs (~90%)
What is the role of Lipoprotein Lipase?
Cleaves TAGs in lipoproteins
What does Lipoprotein lipase need for activation?
Apo C-II
Where is Apo C-II found?
Membrane of TAG-rich lipoproteins, CMs, and VLDL
What functions as a storage for Apo C-II?
HDL
What is LCAT and what is its role?
Lecithin:Cholesterol acyltransferase;
An enzyme that cleaves a fatty acid out of phosphatidyl choline of the HDL membrane and esterifies it to free cholesterol and forms cholesteryl esters in the blood.
What does LCAT need for activation?
Apo A-1
From what does Lipoprotein lipase obtain apo C-II for activation?
HDL
What is Apo A-1? What is it needed for?
Apo A-1 is the main apolipoprotein in the membrane of HDL and is needed for
the reverse cholesterol transport performed by HDL.
Where in the human body is lipoprotein lipase (LPL) synthesized and which hormone favors synthesis and release from fat cells?
Lipoprotein lipase is mainly synthesized in myocardial cells, fat cells and skeletal muscle cells. Synthesis and release are favored by insulin in fat cells.
How is LPL anchored to the capillary walls?
LPL is anchored via a proteoglycan (heparan sulfate) to the endothelial surface of these cells. LPL does not travel within the blood stream.
What is the advantage of anchoring LPL to the walls of capillaries of specific tissues?
The fixed location of extracellular LPL ensures that the released fatty acids from
TAGs are directly available to the heart, skeletal muscle and fat cells.
The LPL isoform of the __________has a higher affinity for TAGs than the isozyme found in _________.
heart;
adipose tissue
Uptake of glucose into fat cells is performed by?
insulin-dependent GLUT-4
Where in the human body is LCAT synthesized and where is its site of action?
- LCAT is synthesized in liver; released as free enzyme into the blood.
- site of action: in blood close to cells that need to get rid of free cholesterol from their plasma membranes.
Which enzyme is needed to fill HDL with cholesteryl esters and needs apo A-1 for enzyme activation and for the recognition of HDL?
LCAT
Which apoprotein is needed for the release of chylomicrons from intestinal cells into the lymph?
The release of chylomicrons into the lymph needs apo B-48
Which two apoproteins are found in the membrane of chylomicron remnants before uptake into the liver?
Chylomicron remnants contain apo E and apo B-48