Cholesterol

Question 1

How many carbon atoms?

Answer 1

27

Question 2

2 facts about the structure?

Answer 2

• Cyclic rings with a hydrophobic tail

- Apart from the hydroxyl group at position 3, the molecule is very hydrophobic

Question 3

Key Property?

Answer 3

Can increase or decrease membrane stifness

Question 4

3 main parts of cholesterol synthesis?

Answer 4

1. Synthesis of isopentenyl pyrophosphate, an activated isoprene
2. Condensation of six molecules of isopentenyl pryophosphate to form squalene
3. Cyclisation and demthylation of squalene by monooxygenases to give cholesterol in the ER

Question 5

What do isoprene units confer to biomolecules?

Answer 5

Lipophilicty

Question 6

All physiological requirements for cholesterol are supplied by the liver through de novo synthesis of cholesterol from acetyl-CoA. In which cellular locations is cholesterol made?

Answer 6

ER and cytoplasm ( all downstream reactions of HMG-CoA- reduction)

Question 7

How is HMG-CoA reductase controlled?

Answer 7

Negative feedback from mevalonate and bile salts

Question 8

Main bile salt and other?

Answer 8

Glycocholate and taurocholate

Question 9

Precursor and enzyme for synthesis of steroid hormones?

Answer 9

Pregnenolone and desmolase

Question 10

What is vitamin D?

Answer 10

Collective group of steroids which are vital for the intestinal absorption of ions needed for bone development like calcium, phosphate and magnesium

Question 11

How is most vitamin D acquired in the West?

Answer 11

UV light catalyses formation of calcitriol

Question 12

What is calcitriol?

Answer 12

Steroid hormone that binds to vitamin D response elements (VDREs) in target genes involved in bone metabolism. Deficiency of Vitamin D3 leads to rickets.

Question 13

Familial Hypercholesterolaemia?

Answer 13

Monogenic dominant trait in which cholesterol transportation is defective

Question 14

Symptoms of FH?

Answer 14

Atherosclerosis and coronary infarction due to high levels of cholesterol

Question 15

Mechanism of FH?

Answer 15

Mutations in LDL receptors can affect receptor expression, LDL binding or LDLR endocytosis and recycling which leads to FH

Question 16

How do resins or sequestrants work?

Answer 16

These bind or sequester bile acid-cholesterol complexes preventing their reabsorption by the intestine. They can lower LDL (“bad” cholesterol) by 15 -30% and raise HDL (“good” cholesterol) by 3 - 5%.



Question 17

How does the drug lovastatin inhibit cholesterol synthesis?

Answer 17

It is a competitive inhibitor of the enzyme HMG-CoA-reductase