14. Cholesterol

Question 1

What makes cholesterol?

Answer 1

Acetyl Coenzyme A

Question 2

What are the 3 steps in cholesterol production?

Answer 2

1. Synthesis of isopentyl pyrophosphate
2. Condensation of 6 molecules of isopentyl pyrophosphate to form squalene
3. Squaline cyclises and the tetracyclic product is converted to cholesterol

Question 3

What are the two ways cholesterol can be obtained?

Answer 3

Exogenously through meat and animal products in the diet

Endogenously made in the liver, intestine and reproductive tissues

Question 4

What is the rate of formation of cholesterol controlled by?

Answer 4

Negative feedback

Question 5

How can the natural production of cholesterol in the liver be inhibited?

Answer 5

HMG-Coenzyme A reductase inhibitors

Eg. Statins

Question 6

How can the absorption of exogenous cholesterol be reduced?

Answer 6

By isolating bile acids in the intestine

Eg. Cholestipol, cholestyramine

Question 7

Which lipoprotein levels are best to reduce the amount of cholesterol in the blood?

Answer 7

Low levels of VLDL production
Increased lipase action
These increase clearance of LDL by the liver
Eg. fibrates

Question 8

How much cholesterol is stored in an adult and where?

Answer 8

140g

Liver, gallbladder, fat cells

Question 9

How is cholesterol transported?

Answer 9

Exported in blood in the form of VLDLs
Converted to LDLs which carry cholesterol esters, especially linnoleate
LDLs transport cholesterol to peripheral tissue and regulate cholesterol production at these sites
HDLs pick up cholesterol released back into plasma by dying cells

Question 10

What are the functions of cholesterol in the body?

Answer 10

Precursor for steroid molecules
Bile acids and bile salts
Steroid hormones
Vitamin D