GI Physiology: Bile

Question 1

How are bile salts reabsorbed?

Answer 1

They are reabsorbed by an Na+/bile salt cotransporter in the ileum

Question 2

What enzyme is responsible for bile acid synthesis?

Answer 2

7-alpha Hydroxylase (inhibited by bile salts)

Question 3

What is the composition of bile?

Answer 3

Bile salts (50%)
Phospholipids (40%)
Cholesterol (4%)
Bilirubin (2%)
H2O and ions

Question 4

What are the primary bile acids?

Answer 4

Cholic acid

chenodeoxycholic acid

Question 5

What are the secondary bile acids?

Answer 5

Deoxycholic acid
Lithocholic acid

Created from primary bile acids by intestinal bacteria

Question 6

How are bile acids converted to bile salts?

Answer 6

The bile acids are conjugated to amino acids
glycine - deoxycholic acid
Taurine - Lithocholic acid

Question 7

What is the pathway of Heme degradation?

Answer 7

RBCs –> Hemeglobin –> bilirubin-albumin –> Liver –> Bilirubin glucaronide –> Bilirubin (bacteria) –> urobilogen –> Stercobilin or urobilin

Question 8

What electrolytes does the liver secrete while forming bile acids?

Answer 8

Ca, K+, Cl-, Na+

Question 9

How does the bile duct alter bile?

Answer 9

Secretes Na+, HCO3-, H2O

Absorbs Cl-