MEH - Lipid Transport Flashcards
How are lipids transported n the body?
98% bound in lipoprotein particles 2% albumin
What do lipoprotein particles consist of (5)?
TAGS, phospholipid, cholesterol, cholesterol esters, proteins
Above what level of cholesterol is a risk?
> 5mM/L
How are different phospholipids classified?
According to their different polar head groups
How much cholesterol do we require a day? What happens if we don’t get that from the diet?
Minimal or none. The liver can synthesise cholesterol directly (most is actually done this way)
3 uses of lipids in the body?
- Bile salts
- Steroid hormones
- Membranes
What is cholesterol transported around the body as? What enzyme catalyses the formation of these?
Cholesterol esters - LCAT
What are apolipoproteins? Which one is associated with bad cholesterol (LDL) , which with good (HDL)?
Specific proteins associated with lipoprotein particles - have functional and structural roles. Groups ABCDEH
ApoB- bad
ApoA1 - good
There are 5 distinct classes of lipoproteins - what are they? What varies in them? Which has the most of each
Chylomicrons, VLDL, LDL, IDL, HDL
They vary in fat content, cholesterol ester, apolipoprotein and cholesterol.
VDLD has most lipid in least protein
HDL has high protein and cholesterol ester content
Why is HDL the smallest in size and VLDL the largest?
Because particle diameter is inversely proportional to density
What are the structural (1) and functional (2) roles of apolipoproteins?
1) Packaging water insoluble lipid
1) cofactors for enzymes
2) ligands for cell surface receptors
What apolipoproteins are added to chylomicrons during their metabolism (3) ?
First ApoB-48 - then they enter lymphatic system
Once enter thoracic duct Apo C and E are added.
Apo C binds to LPL (lipoprotein lipase) on adipocytes and muscle - depletes lipoprotein content
Which receptor binds to ApoC and which to ApoE and where?
LPL - lipoprotein lipase binds to ApoC in skeletal muscle and adipose tissue so the chylomicron depletes it’s contents - when contents depleted to 20% it becomes a chylomicron remnant and ApoC dissociates
LDL - low density lipoprotein receptor in liver - binds to ApoE and the chylomicron remnant is taken up by hepatocytes by endocytosis - lysosomes then contain enzymes for remaining metabolism.
What is the role of lipoprotein lipase?
It is an enzyme that hydrolyses TAGS in lipoproteins - requires apoC as a cofactor - in endothelial cells in capillaries –> FA can then be taken in by skeletal muscle and adipose for use/storage.
What is the different roles of VLDL, LDL, IDL, and HDL?
VLDL - made by liver to transport TAG to other tissues
LDL - provide cholesterol from liver to other tissues
HDL - can remove cholesterol from laden cells and return it to the liver.