Cholesterol and Cholesterol Esters

Question 1

Key Regulators of cholesterol synthesis

Answer 1

mevalonate

HMG-CoA reductase

7 alpha hydroxylase

ACAT (acyl-CoA cholesterol acyl tranferase)

Question 2

What is the predominant form of cholesterol in cells

Answer 2

cholesterol ester

Question 3

What are the steroid hormones derived from cholesterol

Answer 3

progesterone

estradiol

testosterone

dehydroepiandrosterone

cortisol

aldosterone

1,25 dihydroxy vitamine D3 (vitamin)

Question 4

What is the rate limiting enzyme in cholesterol synthesis

Answer 4

HMG-CoA reductase

converts HMG-CoA to mevalonate

Question 5

Regulation of HMG-CoA reductase

Answer 5

promotors: insulin
inhibitors: sterols, non sterol metabolites derived from mevalonate, cholesterol, mevalonate, AMP, low ATP

Question 6

Rate limiting enzyme of bile acid synthesis

Answer 6

7-alpha-hydroxylase

Question 7

What effect does excess cholesterol have on enzyme activity?

Answer 7

decreases HMG-CoA reductase activity. therefore decreases cholesterol synthesis

increases ACAT which caises increased cholesterol storage/utilization

increases 7-alpha-hydroxylase which causes increased bile acid synthesis/utilization

Question 8

What are the effects of decreased cholesterol on enzyme activity

Answer 8

increased HMG-CoA reductase activity which causes increased cholesterol synthesis

decreased ACAT activity which causes decreased cholesterol stoage and utilization

decreased 7-alpha-hydroxylase which causes decreased bile acid synthesis/utilization

Question 9

Squalene

Answer 9

hydrocarbon and triterpene

converted to lanosterol and then to cholesterol, and vitamine D

squaline must go through cyclization by the enzyme cyclase.