Bile acids and salts synthesis

Question 1

The function of bile

Answer 1

helps to emulsify and breakdown fats that we ingest

Question 2

Bile contains …………… and ……………… compounds

Answer 2

organic and inorganic

Question 3

What makes up the inorganic part of bile and what’s the percentage?

Answer 3

water, 95%

Question 4

The major organic component of bile is …….

Answer 4

bile salts

Question 5

The 5 organic compounds in bile salt are

Answer 5

bile acids
lecithin
bilirubin
fatty acids
cholesterol

Question 6

Difference between bile salts and bile acids?

Answer 6

bile salts are conjugated versions of bile acids

Question 7

Where is bile stored in between meals?

Answer 7

in the gall bladder

Question 8

What kind of compound is bile acids and what do they contain?

Answer 8

organic and contain
24C
hydroxyl group
methyl group
carbonyl group

Question 9

In what form do bile acids exist in physiological pH

Answer 9

partially dissociated

Question 10

Bile acids are amphipathic, this means

Answer 10

they have both hydrophobic and hydrophilic properties

Question 11

Bile acids are synthesized from

Answer 11

cholesterol

Question 12

What are the 2 major primary bile acids?

Answer 12

cholic acid

chenodeoxycholic acid

Question 13

The 3 main processes that convert cholesterol to bile acids

Answer 13

1. shortening of hydrocarbon chain by 3C atoms
2. Double bonds are reduced
3. hydroxyl groups with carbonyl groups are added

Question 14

Which enzyme catalyzes the rate-limiting step of bile synthesis and where is it found?

Answer 14

cholesterol 7α hydroxylase and it is an ER bound enzyme

Question 15

The function of cholesterol 7α hydroxylase

Answer 15

adds a hydroxyl group to C7

Question 16

The function of cholesterol 7α hydroxylase

Answer 16

adds a hydroxyl group to C7

Question 17

What activates the upregulation of cholesterol 7α hydroxylase?

Answer 17

high cellular levels of cholesterol

Question 17

What activates the upregulation of cholesterol 7α hydroxylase?

Answer 17

high cellular of cholesterol

Question 18

What activates the down regulation of cholesterol 7α hydroxylase?

Answer 18

high levels of primary bile acids

Question 19

By what mechanism does the down regulation of cholesterol 7α hydroxylase activity occur?

Answer 19

negative feedback

Question 20

cholesterol 7α hydroxylase is only found in

Answer 20

hepatocytes

Question 21

Liver cells can only release bile acids when

Answer 21

they have been conjugated to bile salts

Question 22

How can bile acids be transported?

Answer 22

via transport molecules like albumin to travel in the blood

Question 23

How are bile salts formed?

Answer 23

by the conjugation of bile acids with glycine or taurine at the carboxyl group

Question 24

What does conjugation of bile acids do to their pKa value and ionization?

Answer 24

lowers the pKa value and allows them to exist in their fully ionized form, making them able to dissolve in aqueous solution

Question 25

What makes bile salts better emulsifying agents than bile acids?

Answer 25

conjugation

Question 26

Where does conjugation of bile acids occur?

Answer 26

liver peroxisomes

Question 27

What are the products of conjugation of primary bile acids?

Answer 27

taurine + cholic/chenodeoxycholic acid = taurocholic/chenodeoxycholic acid

glycine + cholic/chenodeoxycholic acid = glycocholic/chenodeoxycholic acid

Question 28

The ratio of glycine to taurine in the body is

Answer 28

3:1

Question 29

What role do bile salts play in cholesterol excretion?

Answer 29

they provide the major method of cholesterol excretion

Question 30

What can bacteria in the duodenum do to bile salts?

Answer 30

they can convert bile salts back to primary bile acids by removing glycine or taurine
they can also convert primary bile acids to secondary bile acids

Question 31

By what methods are secondary bile acids formed by bacteria in the duodenum?

Answer 31

deconjugation and 7α dehydroxylation

Question 32

Name the 2 secondary bile acids and how they are formed?

Answer 32

Deoxycholic acid formed from glycocholic acid

Lithocholic acid formed from tauro-/glyco- chenodeoxycholic acid

Question 33

What happens to the mixture of bile salts, primary bile acids and secondary bile acids in the ileum?

Answer 33

95% of this mixture is actively reabsorbed into the liver

5% is excreted through faeces

Question 34

What do mediations like cholestyramine do to bile acids?

Answer 34

they bind and sequester (isolate) them and prevent their reabsorption

Question 35

What is the importance dietary fibers binding to bile acids?

Answer 35

to promote cholesterol excretion

Question 36

What is the importance dietary fibers binding to bile acids?

Answer 36

to promote cholesterol excretion

Question 37

What is the principal sterol in faeces and how is it formed?

Answer 37

coprostanol and it is formed from cholesterol by the bacteria in the lower intestine

Question 38

What prevents the precipitation of cholesterol in the gall bladder?

Answer 38

bile acids and phospholipids

Question 39

Bile acids facilitate the intestinal absorption of

Answer 39

fat-soluble vitamins

Question 40

What is enterohepatic circulation?

Answer 40

when 98-99% of primary and secondary bile acids are returned to the liver via portal circulation

Question 41

Litholic acid is not absorbed to a large extent because

Answer 41

of its insolubilty