CVR 9

Question 1

Overview of cholesterol

Answer 1

1 of 3 vital components of membrane.
Minor component - 10%
least soluble in water
more rigid than the others
inserts between FA preventing crystallisation

Question 2

Describe the structure of cholesterol?

Answer 2

Branches group, methyl group, steroid group, hydroxyl

4 ring structure with low H20 soluability

Storage esterfied

Question 3

Stages of Cholesterol Synth

Answer 3

isopentenyl pyrophosphate - building block

condesnssation of 6 molecules forming squalene

squalene cycilzes and tetracyclic product is converted to choleserol

Question 4

What and with which enzyme forms isopentenyl pyrophosphate 1

Answer 4

HMG CoA

HMG CoA reuctase

Question 5

ISopentenyl pyrophosphate 2 is formed in 3 stages name them

Answer 5

mevalonate to 5 phosphomelavonate to 5 pyrophosphate mevalonate to 3 isopentenylpyrophosphate

Question 6

How is cholesterol regulated

Answer 6

negative feedback mechanism by changing activity of 3 hydroxy 3 methylglutaryl CoA reductase HMG CoA reductase which is inhibited by Statins

Question 7

How can we control HMG CoA

Answer 7

Rate of reductase mRNA SREBP

Rate of translation of mRNA from nonsterol metabolies derived from mevalonate and dietary cholesterol

Degradatioon of reductase - proeolysis in response to cholestero

phosphorylation decreases the activity of reductase with low ATP

Question 8

Role of LDL and HDL in transport

Answer 8

The role of LDL is to transport cholesterol to peripheral tissue and regulate de novo cholesterol synthesis at these sites
High density lipoproteins (HDL) picks up cholesterol released back into the plasma from dying cells. Acyltransferase in HDL esterifies the cholesterol and then shuttles it back to LDLP or returns it to the liver

Question 9

What drugs regulate cholesterol?

Answer 9

Inhibition of de novo synthesis of cholesterol in the liver – HMG- CoA inhibitors (e.g. statins)

Sequestering bile acids in the intestine (e.g. cholestyramine, colestipol). Reduces the absorption of exogenous cholesterol and increases the metabolism of endogenous cholesterol into bile acids

Altering the relative levels of different lipoproteins: decreasing VLDL production, increasing the activity of lipoprotein lipase and enhancing the clearance of LDL by the liver (e.g. fibrates)

Question 10

What are the derivatives of cholesterol?

Answer 10

Bile salts
Steroid Hormones
Vitamin D

Question 11

Bile relation to cholesteriol

Answer 11

we cannot metabolize cholestero to C02 so we make bile