Cholesterol and bile

Question 1

How is cholesterol packaged?

Answer 1

In VLDLs in the liver with TAGs

Question 2

Mevalonate

Answer 2

Important intermediate in cholesterol synthesis, which is a product of the rate-limiting enzyme HMG-coA reductase

Question 3

HMG-CoA reductase

Answer 3

Enzyme that catalyzes the conversion of HMG-CoA into mevalonate in the rate-limiting step in cholesterol production

Question 4

What are the intermediates from mevalonate to the final formation of cholesterol?

Answer 4

4 Mevalonate -> 2 farnesyl pyrophosphate -> squalene -> lanosterol -> cholesterol

Question 5

The activity of HMG-CoA reductase is regulated by __

Answer 5

the concentration of AMP, mevalonate, cholesterol, and sterols.

Question 6

How do sterols regulate the amount of HMG-CoA reductase?

Answer 6

By binding to the sterol response element (SRE) in the DNA, inhibiting mRNA production

Question 7

What happens to HMG-CoA reductase in the presence of high concentrations of mevalonate and cholesterol?

Answer 7

It is rapidly degraded

Question 8

HMG-CoA reductase phosphorylation

Answer 8

Phosphorylated by an AMP-activated kinase, so cholesterol will not be synthesized when ATP is low

Question 9

Rate-limiting enzyme in bile acid synthesis

Answer 9

7-alpha-hydroxylase

Question 10

Cholesterol excess leads to what changes in enzyme activity?

Answer 10

Increase in ACAT activity
Increase in 7-alpha-hydroxylase activity
Decrease in HMG-CoA reductase

Question 11

Cholesterol deprivation leads to what changes in enzyme activity?

Answer 11

Decrease in ACAT activity
Decrease in 7-alpha-hydroxylase activity
Increase in HMG-CoA reductase