Chapter 12: 12.2 Lipoproteins Flashcards
What is cholesterol important for?
Important for membranes, hormones, bile acids, and vitamin D3
What is cholesterol made from?
Acetyl-CoA
What is HMG-CoA reductase?
Produces mevalonate (major point of regulation in cholesterol production)
What can HMG-CoA reductase be inhibited by?
Phosphorylation
What are competitive inhibitors to HMG-CoA reductase?
Statins
What does HMG-CoA reductase need to for mevalonate?
2 NADPH
In the formation of cholesterol:
—— are used to form ——— units that join to form ——– (—)
- 3 ATPs
- Isoprene
- Squalene (C30)
In the formation of cholesterol:
Where is squalene cyclized to cholesterol?
ER
How many carbons are in cholesterol?
C27
What can be formed through modifications on the hydroxyl groups of cholesterol?
Cholesterol esters (CE)
* Acyl groups added
How is cholesterol transported and where is it transported?
Transported through the bloodstream via lipoprotein complexes
What results in heart attack or stroke?
Oxidized LDL found in arterial plaques
Exercise and diet can raise — and lower —
- Raise HDL
- Lower LDL
What is the purpose of lipoproteins?
- Transport lipids
- Travels through the bloodstream providing energy
What are lipoproteins made up of?
A monolayer of phospholipids, cholesterol, and apoproteins
Where are lipoproteins made?
In the intestine or liver
What happens to any leftover lipoproteins?
Recycled in the liver
What types of lipoproteins are there?
- Chylomicrons
- VLDL
- HDL
Describe:
Chylomicrons
Made in the small intestine
* Contain TAGs and apoprotein 48
Describe:
VLDL
Made in liver
* Contains ApoB100
* Lipoprotein lipase hydrolizes TAGs to produce IDL and LDL
Describe:
HDL
Brings cholesterol and CEs back to the liver for breakdown
* The “good cholesterol” - picks up cholesterol esters via LCAT enzyme
LP uptake by Endocytosis:
What in liver cells bind lipoproteins?
LDL receptors
LP uptake by Endocytosis:
What does receptor-mediated endocytosis occur through?
Via clathrin-coated vesicles
LP uptake by Endocytosis:
What do the clathrin-coated vesicles get fused with?
Fused with lysosomes and get broken down
True or False:
In LP uptake by endocytosis, the receptors are not recycled
False, the receptors are then recycled
What can mutations in the process of recycling receptors result in?
Can increase cholesterol levels
