Lecture 40

Question 1

the 27 Carbons of Cholesterol are all derived from ____

Answer 1

ACETATE

Question 2

The C-3 _____ group can be esterified.

Answer 2

HYDROXYL

Question 3

The C-17 side chain can be modified with a ______carbon tail.

Answer 3

HYDROcarbon tail

Question 4

Cholesterol is mostly reabsorbed in the intestines, but it can be converted into ____ salts and acids and a small % can be excreted in the ____.

Answer 4

Can be converted into BILE salts and acids and a small % can be excreted in the FECES

Question 5

The major form cholesterol is transported throughout the body is the ______ form. It is ______ with a fatty acid.

Answer 5

ESTERIFIED form. It is ESTERIFIED with a Fatty acid

Question 6

In the first part of Cholesterol synth, 2 acetyl CoA molecules are converted to _____CoA.

Answer 6

HMG CoA

Question 7

The rate limiting step of Cholesterol Synthesis is the conversion of HMG CoA to _____ acid via the enzyme _____ reductase (requires NADPH.) This occurs in the _____ reticulum.

Answer 7

Conversion of HMG CoA to MEVALONIC acid via the enzyme HMG CoA reductase (requires NADPH.) This occurs in the ENDOPLASMIC reticulum.

Question 8

How many ATP and NADPH are required to synthesize Cholesterol?

Answer 8

18 ATP and 14 NADPH

Question 9

When intracellular Cholesterol levels are high, transcription of cholesterol synthesis enzymes is ______. The transcription factor responsible for this regulation is ____.

Answer 9

With high intracellular cholesterol levels, transcription of Cholesterol synth genes are INHIBITED by the transcription factor SREBP.

Question 10

When ER sterols are low, ____-SREBP moves to the golgi where two ____ cleave ____ from SREBP, making it soluble so it can translocate to the nucleus.

Answer 10

SCAP_SREBP move to the golgi where two PROTEASES cleave SCAP from SREBP, making it soluble.

Question 11

Regulation of Cholesterol synth can also be mediated by degradation of HMG CoA Reductase (HMGR.) When ER cholesterol levels are low, the HMGR is properly ______. When levels are high, HMGR is mis_____ and degraded.

Answer 11

Low cholesterol levels –> HMGR is properly FOLDED. High levels –> MISFOLDED and degraded.

Question 12

When HMGR is ______, it is inactive. This process is mediated by AMP-activated Kinase

Answer 12

PHOSPHORYLATED

Question 13

Statins act as ______ inhibitors of HMGR by mimicking Melvadyl-CoA

Answer 13

COMPETITIVE inhibitors

Question 14

7-alpha-hydroxylase is involved in the rate limiting step of bile acid synthesis from Cholesterol. It is inhibited by ____ acid and stimulated by _____.

Answer 14

Inhibited by CHOLIC acid, and stimulated by CHOLESTEROL