Cholesterol Metabolism

Question 1

Enzyme for the rate-limiting step in cholesterol metabolism

Answer 1

HMG CoA reductase

Question 2

Acetoacetyl CoA + acetyl CoA = ___

Answer 2

3-hydroxy-3-methylglutaryl (HMG) CoA

Question 3

the action of HMG CoA reductase turns HMG CoA into ___

Answer 3

mevalonate

Question 4

Mevalonate + 2 transfers of phosphate groups from ATP

Answer 4

5-pyrophosphomevalonate

Question 5

Sequence the formation of these compounds after 5-pyrophosphomevalonate

A.farnesyl pyrophosphate
B.isopentyl pyrophosphate
C.3,3-dimethylallyl pyrophosphate
D.geranyl pyrophosphate

Answer 5

B then C then D then A

B.isopentyl phosphate [5-Carbon] C.3,3-dimethylallyl pyrophosphate [5C]—(transferase)–>D. geranyl pyrophosphate [10C]–(transferase)–> A. farnesyl pyrophosphate [15C]

Question 6

The combination of two farnesyl phosphate molecules yields ___, a compound with ___ Carbon atoms via the action of the enzyme __

Answer 6

squalene
30
squalene synthase

Question 7

Squalene converted (througH molecular oxygen, NADPH and the enzyme ____) to ___, a 27C compound

Answer 7

squalene monoxygenase

lanosterol

Question 8

True or False: Lanosterol has more carbon atoms than cholesterol

Answer 8

false; cholesterol and lanosterol both have 27 carbon atoms

Question 9

Rate limiting step @ bile acid synthesis: introduction of ____ of the steroid nucleus by the enzyme ____

Answer 9

hydroxyl group at C7

cholesterol-7-alpha-hydroxylase

Question 10

Bile salts: bile acids conjugated to ___ or ___ by an ___ bond between the carboxyl group of the bile acid and amino group of the added compound

Answer 10

glycine
taurine
amide

Question 11

As lipoproteins transport lipids to the different organs, there is no gradual deposition of lipids in the peripheral tissues. True or false?

Answer 11

false; there is gradual deposition of lipids :)

Question 12

False about chylomicrons

a. assembled in the liver
b. start with apo-B-48 synthesis in the RER
c. have lower density than low-density lipoprotein
d. none of the above

Answer 12

a. assembled in the liver

intestinal mucosal cells dapat

Question 13

apo B-48 loaded with lipid by _____ = chylomicron

Answer 13

microsomal triacylglycerol transfer protein

Question 14

The chylomicrons released by intestinal mucosa are functionally complete, true or false?

Answer 14

False. They need to be rapidly modified in the plasma by apo E and apo C(from circulating HDL) to achieve full functionality.

Question 15

Remnant chylomicron is processed in what organ?

a. small intestine
b. pancreas
c. liver
d. all of the above

Answer 15

c. liver

Question 16

False about VLDL
A. high TAG content
B.more dense than CM
C. synthesized in the plasma

Answer 16

c. synthesized in the plasma

yung totoo: VLDL is synthesised in the liver from triacylglycerol packaged with cholesterol, apo B-100 and phospholipids

Question 17

As VLDL is circulated, it VLDL decreases in size and becomes denser + exchanges materials with HDL (process catalysed by ____)

Answer 17

cholesteryl ester transfer protein

Question 18

LDL delivers cholesterol to the peripheral tissues (or return it to the liver) by binding to cell surface membrane LDL receptors that recognize apo B-48. True or false?

Answer 18

False. apo B-100, not apo B-48

Question 19

LDL receptors (negatively charged glycoproteins) are in pits whose shapes are stabilised by ___

Answer 19

clathrin

Question 20

high cholesterol (stimulates, inhibits) HMG CoA reductase

Answer 20

inhibits

Question 21

lipoprotein with highest protein content

Answer 21

HDL

Question 22

HDL is a circulating reservoir of apolipoproteins: ___ and ___

Answer 22

apo C-II

apo E

Question 23

main functions of HDL: uptake of ____ from ____ and return to ____ as _____

Answer 23

uptake of unesterified cholesterol from non-hepatic tissues and return to the liver as cholesteryl esters

Question 24

Which lipoprotein is termed as “good cholesterol”?

a. VLDL
b. HDL
c. LDL
d. chylomicrons
e. all of them are termed as such

Answer 24

b. HDL

Question 25

Which lipoprotein is termed as “bad cholesterol”?

a. VLDL
b. HDL
c. LDL
d. chylomicrons
e. all of them are termed as such

Answer 25

c. LDL