12 - Intro to Cholesterol

Question 0

Cholesterol is the precursor for what 4 major types of compounds?

Answer 0

bile acids, vitamin D, corticosteroids, and sex hormones

Question 1

What compound is the source of all carbons in cholesterol?

Answer 1

Acetyl CoA

Question 2

What are the five stages of cholesterol biosynthesis that we discussed and their products?

Answer 2

1. Mevalonate Synthesis: Mevalonate + 2 NADP + CoASH
2. Isoprenoid Synthesis: Isopentyl-phyrophosphate + CO2 + Pi
3. Squalene Synthesis: Squalene + NAD+ + 2PP_i
4. Lanosterol Synethsis: Lanosterol
5. Synethsis of Cholesterol from Lanosterol: Cholesterol + NADP+

Question 3

What are the substrate, enzyme, and product, of the rate-limiting step of cholesterol synthesis

Answer 3

Substrate: HMG-CoA, 2 NADPH, + 2H+

Enzyme: HMG-CoA reductase

Products : Mevalonate + 2 NADP+ + CoASH

Question 4

What are the different means by which cholesterol Synthesis is controlled naturally?

Answer 4

Bi-Cylic Control Mechanism regulates the rate limiting step via phosphorylation/dephosphorylation based upon circulating glucagon vs. insulin levels

Genetic mechanisms

Question 5

What are the main dietary source of cholesterol? How does our body get rid of cholesterol?

Answer 5

Fatty meats: Liver

Get rid of: Feces

Question 6

What are bile salts and their use? What is the route of circulation for their re-absorption?

Answer 6

Biles salts are from cholic acid, which can react with amino acids to form amides.

They are released by the gall bladder (to solubilize dietary fats) and taken up by portal vein (enterohaptic circulation).

Question 7

In what two ways is pharmaceutical intervention used to lower patient cholesterol levels?

Answer 7

1) Drugs can reduce HMG -CoA reductase concentration to reduce mevalonate production (thus less cholesterol is produced)
2) Drugs can increase bile salt production, which decreases cholesterol level. This reduces amount of cholesterol available for HDL to return or LDL to deliver to tissues.