Curbing Cholesterol Flashcards
Some cholesterol is obtained from diet, but where does the majority come from?
Synthesised in the LIVER
What roles does cholesterol play in the body?
Plasma membrane component
Precursor for steroid hormones
Precursor of bile acids
In what form is cholesterol transported around the body?
Cholesterol ester (Cholesterol linked to fatty acid)
Within lipoproteins
What are the 5 distinct classes of lipoproteins? (MEH 4.2)
Chylomicrons
VLDL
IDL
LDL
HDL
98% of lipids are carried as what? Are these molecules or particles?
Lipoprotein particles
Particles
Lipoprotein particles are made up of what components?
Peripheral apolipoproteins (ApoC, ApoE)
Integral apolipoproteins (ApoA, ApoB)
Phospholipid monolayer
Cargo- TAG, cholesterol ester, fat soluble vitamins
Particle diameter of lipoproteins is inversely proportional to what?
Density
The larger the diameter of lipoprotein, the ________ its density
Lower
Apolipoproteins have two roles in lipid transport, what are they?
Structural: packaging water insoluble molecules
Functional: co-factor for enzymes +ligands for cell surface receptors
How is dietary fat transported once it reaches the small intestine?
In chylomicrons + ApoB
Via lymphatics to thoracic duct which drains into the LEFT SUBCLAVIAN VEIN
Then acquires ApoC and ApoE once in blood
ApoC binds LPL- released fatty acids enter cells
Chylomicron remnants return to the liver, taken up after recognition of ApoE
Where are very low density lipoproteins formed, for what purpose?
Formed in the liver
To transport TAG to other tissues
Muscle: fatty acids used for energy
Adipose: fatty acids coverted back to TAG and stored
As the TAG content of VLDL decreases at the tissues, what happens to the VLDL particles?
Some of them dissociate from the LPL enzyme and return to the liver
(Depleted to 30%:) Some of them become intermediate density lipoproteins (IDLs)
(Depleted to 10%:) Some of them become LOW density lipoproteins (LDLs)
What is a key difference between HDLs and LDLs that prevent them from being efficienty cleared by the liver?
Lack ApoC and ApoE which liver LDL receptors have a high affinity for
This means they have a much longer half life making them more susceptible to oxidative damage
Oxidised LDL is taken up by macrophages and transform to foam cells
Contribute to atherosclerotic plaques
How does LDL enter cells?
Receptor mediated endocytosis
What is the main role of HDLs and how does this have a protective effect on individuals?
Remove excess cholesterol from cells with high levels of cholesterol and return it back to the liver
Disposes as bile salts and to cells requiring additional cholesterol
Reduce likelihood of foam cell and atherosclerotic plaque formation
