Quiz 3 Cholesterol Synthesis

Question 1

Nearly all tissues can synthesize cholesterol from what?

Answer 1

Acetyl CoA

Question 2

20% of cholesterol synthesis happens where?

Answer 2

In the liver

Question 3

Extrahepatic sites cholesterol can be synthesized?

Answer 3

Intestine, adrenal cortex, reproductive tissues

Question 4

Chylomicron remnants go to where and converted to bile salts?

Answer 4

liver

Question 5

Free cholesterol is an essential component of what?

Answer 5

cell membranes (this regulates the fluidty, gives strength to the membrane)

Question 6

Free cholesterol is precursor to?

Answer 6

bile salts and steroid hormones

Question 7

Type of cholesterol not located in membranes and is MORE hydrophobic?

Answer 7

esterfied cholesterol

Question 8

What are two outcomes of excess cholesterol?

Answer 8

Gallstones and Atherosclerosis (cholesterol deposited at the linings of blood vessels)

Question 9

30% of circulating cholesterol is this form?

Answer 9

Free cholesterol

Question 10

Cholesterol Synthesis occurs where in the cell?

Answer 10

Cytosol

Question 11

Reducing power of cholesterol synthesis?

Answer 11

NADPH

Question 12

What things are required in cholesterol synthesis?

Answer 12

ATP, molecular O2, Acetyl CoA

Question 13

What are the 3 stages of cholesterol synthesis?

Answer 13

Stage 1: 3 Acetyl CoA → HMG-COA
Stage 2: HMG-CoA → Mevalonic Acid (mevalonate) → Squalene
Stage 3: Squalene → Cholesterol

Question 14

What is the rate-limiting, key regulatory step of cholesterol synthesis?

Answer 14

HMG-CoA reductase (remember this occurs in the cytosol)

Question 15

Product of HMG-CoA Reductase?

Answer 15

Mevalonate (mevalonic acid)

Question 16

Is HMG CoA reductase reversible or irreversible?

Answer 16

IRREVERSIBLE

Question 17

As cholesterol concentration increases, what does this do to HMG CoA reductase?

Answer 17

Inhibits it (low cholesterol levels stimulate this enzyme)

Question 18

HMG CoA reductase is active or inactive (inhibited) when phosphorylated by AMP-activated protein kinase?

Answer 18

Inhibited when phosphorylated (stimulated when non-phosphorylated)

Question 19

Competitive inhibitors of HMG CoA reductase which block endogenous synthesis of cholesterol?

Answer 19

Statins

Question 20

What type of bile salts are made in the liver and then secreted into the duodenum?

Answer 20

Primary bile salts

Question 21

Which type of bile salts are made in the intestine?

Answer 21

Secondary bile salts

Question 22

All bile salts end in?

Answer 22

Cholic acid or cholate

Question 23

Difference in polar and non polar bile salts?

Answer 23

Number and position of hydroxyl groups

Question 24

What is the precursor for all steroid hormones?

Answer 24

Pregnenolone

Question 25

Cholesterol synthesis an energy requiring pathway?

Answer 25

YES!! Lots of energy required

Question 26

What are the ingredients again for Cholesterol synthesis?

Answer 26

Acetyl CoA, NADPH. O2, and ATP

Question 27

What is the first unique compound in cholesterol synthesis?

Answer 27

Mevalonate

Question 28

Cholesterol is a precursor for?

Answer 28

Bile Salts and steroid hormones

Question 29

Can cholesterol be degregaded? If not how is it excreted?

Answer 29

No, excreted in bile

Question 30

Glucose, fructose, insulin, thyroxine stimulate or inhibit cholesterol synthesis?

Answer 30

Stimulate

Question 31

Glucagon, epinephrine, and statins inhibit or stimulate cholesterol synthesis?

Answer 31

Inhibit