Lipid Metab -1b

Question 0

Cholesterol is the precursor of:

Answer 0

vit D (skin)
Bile acids (liver)
Steroid hormones (adrenals and glands)

Question 1

Important component of membranes and outer layer of lipoproteins

Answer 1

Cholesterol

Question 2

Protects gallbladder membrane from harmful effects of bile salts

Answer 2

Cholesterol

Question 3

Organ that have the greatest capacity to synthesize cholesterol

Answer 3

Iiver
Intestine
Adrenal cortex
Gonads 
Placenta

Question 4

All carbon atoms of cholesterol are derived from

Answer 4

Acetyl-CoA

Question 5

Cholesterol synthesis takes place in the ——–

Answer 5

Cytosol and ER

700mg/day

Question 6

How many ATPs do you need to synthesize cholesterol?

Answer 6

18 ATP/cholesterol

Question 7

Five steps in the synthesis of cholesterol

Answer 7

1. Biosynthesis of mevalonate (rate-limiting)
2. Formation of isoprenoid units/ isopentenyl pyrophosphate
3. Formation of squalene
4. Cyclization of squalene to lanosterol
5. Conversion of lanosterol to cholesterol

Question 8

Rate limiting step in the synthesis of cholesterol

Answer 8

1. Biosynthesis/formation of MEVALONATE

Question 9

Committed enzyme in the rate limiting step in synthesis of cholesterol

Answer 9

HMG-CoA reductase

Question 10

An intrinsic membrane protein of the ER and its active site extnds to the cytosol

Answer 10

HMG-CoA reductase

Question 11

Hormone that Stimulates HMG-CoA reductase

Answer 11

Insulin

Question 12

Hormone that Inhibits HMG-CoA reductase

Answer 12

Glucagon

Question 13

Cholesterol inhibits HMG-CoA reductase by what mechanism?

Answer 13

Feedback inhibition

Question 14

Drugs that inhibit HMG-CoA reductase

Answer 14

“Statins”

Question 15

Sequential phosphorylation of mevalonate by kinases utilizing ATP;
Takes place several times; most expensive

Answer 15

Step 2 of cholesterol synthesis

Formation of isoprenoid units/isopentenyl phosphate

Question 16

How many isoprenoid units does it take to make 1 cholesterol?

Answer 16

6 isoprenoid units

Question 17

1 mevalonate to 1 isop unit = ? ATP

Answer 17

3 ATPs

Question 18

6 isoprenoid units to 1 cholesterol = ? ATP

Answer 18

18 ATPs

Question 19

Involves initial ismoerization & then condensation of isopentenyl pyrophosphate (c-5)

Answer 19

Step 3 of cholesterol synthesis

Formation of squalene

Question 20

(2) two isopentenyl-PP condenses to form

Answer 20

Geranyl pyrophosphate (c-10)

Question 21

(1) one gernayl pyrophosphate condenses wt (1) one IPP to form

Answer 21

Farnesyl pyrophosphate (c-15)

Question 22

(2) two farnesyl PP condenses to form

Answer 22

Squalene (c-30)

Question 23

Enzyme responsible for the cyclization of squalene to lanosterol

Answer 23

ER-bound squalene oxidocyclase

Question 24

2 enzymatic activities of squalene oxidocyclase

Answer 24

• epoxidase (monooxygenase)

- cyclase (oxidosqualene : lanosterol cyclase)

Question 25

Major route from lanosterol to cholesterol

Answer 25

Lanosterol -> 7-dehydrocholesterol -> cholesterol

Question 26

Alt route from lanosterol to cholesterol

Answer 26

Lanosterol -> zymosterol -> desmosterol -> cholesterol

Question 27

Hydrolysis of stored TAG in adipose tissue; mobilization of fatty accids from TAG stored in adipose tissue

Answer 27

Lipolysis

Question 28

Key enzyme involved in lipolysis

Answer 28

Hormone-sensitive TAG lipase

Question 29

Covalently modulated regulatory enzyme

Answer 29

Hormone-sensitive TAG lipase

Question 30

Hormone-sensitive TAG lipase is regulated by ——–

Answer 30

Hormones acting thru cAMP

Question 31

Hormone-sensitive TAG lipase is activated thru ——-

Answer 31

Phosphorylation reaction catalyzed by protein kinase

Question 32

Principal means by whc FAs are oxidized to generate enery (ATP)

Answer 32

Beta oxidation

Question 33

Where does beta oxidation take place?

Answer 33

Mitochondria

Question 34

Involves removal of 2 carbon atoms at a time starting from the carboxyl end of the fatty acid

Answer 34

Beta oxidation

Question 35

Major end product of beta-oxidation

Answer 35

Acetyl-CoA