Lipoproteins 1 Flashcards
What is a apolipoprotein?
Enzyme activator involved in lipid metabolism, act has a ligand for various tissues (at least 10 exist)
What types of lipoproteins are Exogenous?
Chylomicrons
What types of lipoproteins are Endogenous?
VLDLs, LDLs, IDLs, HDLs
What is the main source of fat in the North American diet?
Triglycerides (95%) - 100-150 grams/day
Why is pure rapeseed oil not good to use?
Very rich in erucic acid (omega 9) which is considered toxic
The non-GMO strain of rapeseed (00) is called what? Why is it safe?
Canola oil, greatly reduced in erucic acid
What type of fats increase cholesterol?
Trans and saturated
What do lipoprotein lipases do?
Chop us fatty acids (FAs) off Triacylglycerides (TAGs)
What are chylomicrons?
Large, least dense lipoproteins that takes lipids from the intestine and takes TAGs to deliver them to the blood vessel wall
Takes the rest towards the liver
What are micelles composed of?
Bile salts and phopholipids - much smaller than fat globules
What does it mean when fatty acids and micelles are partitioned across the water layer?
Passively diffused uptake based oh concentration of FA in cell
Why is cholesterol harder to absorb into the cell?
It is esterified - harder to make into micelles
Where are chylomicrons assembled in the enterocyte?
ER
Fatty acids are reassembled in the ____ into ____ by ___.
ER, TAGs, apoproteins
Which apoprotein activates Lipoprotein lipase (LPL)?
APO-CII
How do LPLs do with chylomicrons? What is the process called?
LPLs hydrolyze them, then release free FAs (by digesting TAGs) into cells
Exogenous transport system
What is done with the left over chylomicrons?
They are taken up by endocytosis into the liver
The chylomicrons also take some cholesterol esters with them
Also carry lipid soluble vitamins (A, D, E, K)
What does the liver do when there its more fat uptake than it need? What is the process?
Excess FA is converted into TAGs and packaged into VLDLs which are secreted via the Endogenous transport system
APO-CII activates LPL which hydrolyzes TAGs to release free FAs for cell uptake - makes fuel, milk or is stored
What happens to leftover VLDLs?
They still have apoE so 50% are taken up by the liver
How are LDLs formed?
By the other half of non-absorbed VLDLs with their TAGs removed by hepatic lipase
LDLs are higher in:
Cholesterol and cholesterol esters
60% of LDLs bind to apoB-100 and taken to the liver. What happens to the rest?
Goes to cells (adrenocortical/gonadal) to make steroid hormones
Also needed for membrane fluidly and vit D synth
What are 3 ways HDLs can be made?
De novo synthesized by liver and intestine (ER)
Generated from chylomircon and VLDL remnants
Apoprotein Al will acquire phospholipids and cholesterol
How does HDL prevent cholesterol from flipping HDL into the outter leaf of a cell membrane so that cholesterol can’t be picked up?
It uses Lecithin: Cholesterol acyltransferase (LCAT)
What is the main action of LDL?
Its the main cholesterol transporter delivering cholesterol to blood vessel wall and liver
What is the main action of HDL?
Removed cholesterol from blood vessel wall and transport cholesterol ester to LDLs
What is the main action of VLDL?
Transport triglycerides and cholesterol from liver and deliver them to blood vessel walls
