Session 2 Flashcards
(29 cards)
How are fatty acids carried in the blood ?
Bound to albumin
What is the ideal level of a fasted TAG blood test?
<2mmol/L
What is the idea level of cholesterol in the blood?
<5mmol/L
What is the ideal level of NON HDL cholesterol in the blood?
<4mmol/L
What is the ideal level of LDL cholesterol in the blood?
<3mmol/L
What is the ideal total cholesterol:HDL cholesterol in the blood?
Less than 6
Above 6 = high risk
What 2 enzymes convert cholesterol to a cholesterol Ester?
LCAT (lecithin cholesterol acyl transferase)
Acyl Coenzyme A
What is the function of chylomicrons ?
When are they found in the blood?
Carry dietary fat to tissues
Present in blood 4-6 hours after a meal
Describe the metabolism of chylomicrons
- Loaded in small intestine, apoB-48 added
- Enter lymphatics
- Enter thoracic duct to left subclavian vein
- Enter blood, ApoC and ApoE added
- ApoC binds to LPL on adipocytes/muscle
- Fatty acids enter cells
- Triglyceride lowers to 20%, dissociates from LPL and becomes chylomicrons remnant
- Travels back to liver
- LDL receptor binds to ApoE, receptor mediated endocytosis
- Lysosomes release remaining contents for metabolism.
What is the cofactor for LPL?
What is the fate of FA?
What is the fate of glycerol?
ApoC - II
Energy/TAG stores
To liver for metabolism
What is the function of VLDL?
Carries TAG synthesised in liver to adipose tissues
Describe VLDL metabolism up until it reaches LPL
- ApoB100 added during for formation
- ApoC and ApoE added from HDL in blood
- Binds to LPL
Describe how IDL forms from VLDL
At around 30% TAG, a short lives IDL forms.
1. Goes back to LPL to deplete TAG
or
2. Take up by liver for metabolism
Describe how LDL forms from IDL
At 10% of TAG, IDL loses ApoC and ApoE and becomes LDL
What is the function of LDL?
Transport of cholesterol synthesised in the liver to tissues
How to peripheral tissues take up LDL
Have LDL receptors, of which the ligand is ApoB-100.
Expression of LDL receptors controlled by cholesterol concentration in the cell.
Receptor mediated endocytosis and lysosomes degrade contents.
Why is LDL not cleared by the liver?
No ApoC or ApoE.
Liver LDL has high ApoE affinity.
What is the problem of LDL?
It has a long half life which increases the change of oxidative damage.
Oxidised LDL taken up by macrophages that become foam cells. This causes atherosclerotic plaques.
What is the function of HDL
Transport of excess cholesterol from cells to liver.
How does HDL form?
Nascent form from liver and intestine.
Budding off from chylomicrons/VLDL at LPL
Free ApoA-I aquires cholesterol and phospholipid.
How does HDL mature?
Accumulates phospholipid and cholesterol from cells lining blood vessels.
Fills and becomes more globular,
No enzymes.
How does HBL metabolise?
Removal of cholesterol which is taken to the liver.
Reduces foam cells and therefore reduced risk of atherosclerotic plaques.
How does cholesterol enter the HDL from the cell?
ABCA1 protein, LCAT makes it an Ester
What are the 3 fates of mature HDL?
- Taken up by liver and forms bile salts
- Scavenger receptor (SR-B1) on cells needing cholesterol for steroid hormones.
- Cholesterol exchange transfer protein (CETP) allows TAG from VLDL to swap for cholesterol Ester in HDL.
