Biochemistry of Bile FC Flashcards

1
Q

Questions

A

Answers

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2
Q

What are the 4 components of bile? (From most to least)

A

Bile Acids
Phospholipids
Cholesterol
Bile Pigments

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3
Q

What is the enzyme for the rate limiting step in bile synthesis? What does it add? What 4 things does it require?

A

7alpha-hydroxylase
Add hydroxyl group to cholesterol
Requires NADPH, O2, Vitamin C, and Cytochrome P450

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4
Q

What enzyme is used in the second step of bile acid synthesis? What 3 things are required at this step? What two things are changed at this step?

A

12alpha-hydrozylase
NADPH, O2, and CoA
B-ring saturated and Propionyl-CoA obtained (where acid now is)

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5
Q

What two bile salts/acids are initially obtained before conjugation? Which one predominates in humans?

A
Cholic acid (predominates in humans, extra OH)
Chenodeoxycholic acid
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6
Q

What two molecules are used to conjugate cholic/chenodeozycholic acid?

A

Taurine or glycine

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7
Q

What are the 4 primary bile salts?

A

Taurocholic acid
Glycocholic acid
Taurochenodeoxycholic acid
Clycochenodeoxycholic acid

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8
Q

What is the pH of bile?

A

Alkaline 7.6-8.4

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9
Q

How are secondary bile acids formed? What are the two major ones?

A

By intestinal bacteria

Deoxycholic acid and Lithocholic acid

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10
Q

Where are both primary and secondary acids reabsorbed? Which one can not be reabsorbed?

A
Ileum
Lithocholic acid (cannot be reabsorbed due to limited solubility)
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11
Q

What does heme oxygenase do?

A

Converts heme to biliverdin

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12
Q

What does biliverdin reductase do?

A

Converts bilverdin to bilirubin

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13
Q

During what step of heme catabolism is carbon monoxide produced?

A

Heme oxygenase (heme to biliverdin)

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14
Q

What is readily reused after being oxidized at the heme oxygenase step?

A

Fe3+

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15
Q

How is bilirubin transported to the liver? Bound to what?

A

Blood

Bound to albumin

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16
Q

What is bilrubin conjugated to in the liver?

A

Diglucuronide

17
Q

Where is diglucuronide converted to urobilinogen? By what?

A

Colon

Intestinal bacteria

18
Q

Metabolized urobiliogen, stercohilinogen, is excreted how?

A

Feces

19
Q

Absorbed urobiliogen is excreted how? Its oxidized to form what?

A

Urine

Uribilin - yellow color to urine

20
Q

Is unconjugated bilirubin insoluble or soluble? Conjugated?

A

Unconjugated - poorly soluble

Conjugated - soluble