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Flashcards in Cholesterol Deck (14)
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1

What is mevalonate?

An intermediate in cholesterol synthesis

2

What is the enzyme that catalyzes the reaction forming mevalonate?

Formed in a reaction catalyzed by HMG- CoA reductase

3

What is the rate limiting enzyme in cholesterol biosynthesis?

HMG- CoA reductase

4

What is squalene?

It is converted to lanosterol which is then converted to cholesterol

5

What activates HMG- CoA reductase?

Insulin

6

What inhibits HMG- CoA reductase?

AMP
Glucagon
High cholesterol levels

7

How is HMG- CoA reductase regulated at the transcriptional level?

Inhibited by sterols like cholesterol

8

How is HMG- CoA reductase regulated at the translational level?

Inhibited by non sterol metabolites derived from mevalonate

9

How is HMG- CoA reductase regulated at the enzyme level?

Degradation is promoted by it s products, mevalonate and cholesterol

10

How is HMG- CoA reductase regulated at the activity level?

Phosphorylation inhibits like via AMP and glucagon

11

What is the rate limiting enzyme in bile acid synthesis?

7-α-hydroxylase

12

What is the function of acyl-CoA cholesterol acyl-transferase (ACAT)?

Converts cholesterol to cholesterol ester

13

What is the effect of increased levels of cholesterol on enzymes in the pathway?

- Inhibits HMG-CoA reductase (decreased cholesterol synthesis)
- Activates ACAT
(increased cholesterol storage/utilization)
- Activates 7-a-hydroxylase
(increased bile acid synthesis/utilization)

14

What is the effect of decreased levels of cholesterol on enzymes in the pathway?

- Activates: HMG-CoA reductase (increased cholesterol synthesis)
- Inhibits: ACAT
(decreased cholesterol storage/utilization)
- Inhibits: 7-a-hydroxylase
(decreased bile acid synthesis/utilization)

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