Cholesterol and Bile Salts

Question 1

Bile Salts

1. primary bile salts ?
2. secondary bile salts ?

Answer 1

1. Cholic acid and chenodeoxycholic acid
2. Deoxycholic and Lithocholic

Question 2

bile acids contain how many carbons ?

what is the rate limiting step in bile-acid synthesis ?

where are hydroxyl groups inserted in bile acids

what part of the ring is reduced ?

what type of vitamin does this need?

the side chain is shortened by how many carbons ?

Answer 2

24

introduction of the hydroxyl group at C7 by hydroxylase

in specific positions of the steroid

the B ring

Vitamin C

three carbons

Question 3

Degradation of cholesterol

1. cholesterol is metabolized and degraded by ?
2. how is it removed
3. how else is cholesterol removed

Answer 3

1. removed from the body by converting it to bile acids and bile salts
2. from the intestine and eliminates in feces
3. by bacteria

Question 4

Synthesis of cholesterol

1. Main places (tissues) that produce cholesterol ?
2. where does cholesterol synthesis happen/occur ?
3. what is the rate limiting/ regulating enzyme for cholesterol synthesis ?
4. Define what HMG-CoA synthase is ?

Answer 4

1. Liver, intestine, adrenal cortex and reproductive tissues
2. cytosol and ER
3. HMG-CoA reductase
4. an enzyme that is used for ketone body synthesis

Question 5

The conversion of LANOSTEROL to CHOLESTEROL

1. involves the shortening of how many carbons ?
2. involves the removal of a methyl group in what carbon number ?
3. migration of the double from C-8 to where ?
4. what happens in Carbon -24 and Carbon -25

Answer 5

1. 30 to 27 carbons
2. carbon 4
3. C - 5
4. reduction of the double bond

Question 6

Cholesterol Traits

Answer 6

Precursor of bile acids

steroid

hormones

vitamin D

Question 7

Aspirin

Answer 7

inhibits thromboxane A2

the synthesis of arachidonic acid from platelets.

lowers the risk of stroke and heart attack by decreasing formation of blood clot

Question 8

Function of Eicosanoids

1. Causes contraction of smooth muscle ? (child birth)
2. PGA , PGE and PG12
3. promotes constriction and formation of clots ?
4. decreases the secretion of gastric HCI ?
5. what else do eisosanoids do ?

Answer 8

1. prostaglandins
2. vasodilation
3. TXA2
4. prostaglandins
5. retain water and sodium ions

Question 9

Regulation of Cholesterol

phosphorylated form indicates INACTIVE form of HMG-CoA

Answer 9

• Sterol- Dependent
• Expression of HMG-CoA reductase
• Phosphorylation and dephosphorylation of HMG-Coa Reducatase
• INSULIN - causes increase in HMG-CoA synthesis (anabolic)
• Glucagon - opposite of insulin (catabolic)