Bile Metabolism

Question 1

Are Lipids (by themselves) are readily absorbed in the small intestine?

Answer 1

FALSE

They are hydrophobic and CANNOT cross the Unstirred Water Layer

Question 2

The unstirred water layer results solely from laminar flow?

Answer 2

FALSE

It comes from Laminar Flow, Mucus, and HCO3

Question 3

Bile forms the structure of the micelle?

Answer 3

TRUE

A Micelle has a Bile protective layer around digested Lipids and Pancreatic Lipase

Question 4

Micelles taxi the digested lipids to the enterocytes?

Answer 4

TRUE

They taxi the digested Lipids across the Unstirred Water Layer and drop them off so they can diffuse across

Question 5

Bile is synthesized in hepatocytes?

Answer 5

TRUE

Hepatocytes secrete Bile into Bile Canaliculi where it can be secreted into Bile Ducts

Question 6

Primary bile acids are synthesized from a cholesterol backbone and they are only hydrophilic?

Answer 6

FALSE

Primary bile acids are synthesized from a cholesterol backbone (non-polar) and they are AMPHIPATHIC due to the conjugated Taurine or Glycine (polar)

Question 7

Only 50% of primary bile is conjugated with glycine or taurine?

Answer 7

FALSE

100% of Primary Bile is conjugated with Glycine or Taurine

Question 8

Bile secretions are near isoosmotic to plasma?

Answer 8

TRUE

Bile osmolarity is basically the same as that of the Plasma, so this allows for “Solvent Drag.” Bile is en effective Buffer because due to Solvent Drag when Bile is secreted Water follows and Solutes (Na+, Cl-, HCO3-) follow Water.

Question 9

Do Bile secretions make a good buffer?

Answer 9

TRUE

Due to Solvent Drag. Bile is near isoosmotic to plasma so when Bile is secreted water follows the Bile and Solutes Solutes (Na+, Cl-, HCO3-) follow the water making Bile secretion an effective buffer

Question 10

Bile secretions are near isoosmotic to plasma?

Answer 10

TRUE

Bile osmolarity is basically the same as that of the Plasma, so this allows for “Solvent Drag.” Bile is an effective Buffer because due to Solvent Drag when Bile is secreted Water follows and Solutes (Na+, Cl-, HCO3-) follow Water.

Question 11

Bile recycling occurs throughout the small intestine?

Answer 11

FALSE

Bile recycling only occurs in the Terminal Ileum

Question 12

The excretion of bile in feces removes some of the cholesterol, bilirubin and random waste products from the body?

Answer 12

TRUE

Around 10% of Bile is excreted and lost to Feces during each cycle

Question 13

Gastrin leads to an increase in what?

Answer 13

1. HCl production by Parietal Cells

2. Lower GI Motility

Question 14

What do Bile Salts do to Lipid Droplets in the Intestines?

Answer 14

Bile Salts surround the Lipids and start to emulsify them to increase their Surface Area

Question 15

How does Pancreatic Lipase begin to digest Lipid droplets?

Answer 15

1. CCK causes the release of Pancreatic Enzymes (Proteases, Lipase, Amylase) into the Duodenum
2. Trypsinogen (a Protease secreted by the Pancreas in its inactive zymogen form) is activated into Trypsin by the Enterokinase (EK) the Duodenum
3. Trypsin activates other inactive zymogen Proteases that was secreted by the Pancreas
4. Pre-Colipase is activated into Colipase
5. Colipase (polar) binds to the polar portion of the Bile protective layer and opens a “door” for the Lipase (non-polar) to enter
6. Pancreatic Lipase begins to hydrolyze the Lipids into Monoglycerides, Free Fatty Acids, and Cholesterol
7. This structure is officially a Micelle

Question 16

What is the function of Micelles?

Answer 16

To “Taxi” the lipid across the Unstirred Water Layer so that the lipids (now Monoglycerides, Phospholipids, and Free Fatty Acids) can diffuse into the Cytosol of the Enterocytes

Question 17

What happens after the removal of the Gallbladder (Cholecystectomy)?

Answer 17

1. NO Bile Storage
2. Increased Bile Production by the Liver
3. Decreased Bile Recycling (lack of storage means more sitting in the ducts so less is reabsorbed)
4. More Bile in the Feces (looser stools and possibly diarrhea)
5. Possibly Upper Right Quadrant pain

Question 18

What happens after Ileal resection?

Answer 18

1. NO Bile Recycling
2. Increased Bile Production by the Liver
3. Severe Diarrhea (Bile draws water and Solutes into the GI tract that cannot be reabsorbed)

Question 19

How can you treat the diarrhea developed due to Cholecystectomy (Gallbladder removal)?

Answer 19

Cholestyramine (binds to Bile and makes it less osmotic)

Question 20

How does Bile contribute to Bilirubin excretion?

Answer 20

1. Colonic Bacteria removes the Glucuronic Acid from Bilirubin that is in Bile and converts it to Urobilinogen
2. Most of the Urobilinogen is oxidized into Stercobilin (brown) and excreted as feces
3. 10-20% of Urobilinogen is recycled into the Portal System and the Liver puts it into the blood where it is filtered and converted to Urobilin (yellow) and excreted in the Urine

Question 21

What makes Feces brown? How is it formed?

Answer 21

1. Stercobilin
2. Colonic Bacteria removes acid from Bilirubin converting it into Urobilinogen. Most of the Urobilinogen is oxidized into Stercobilin

Question 22

What makes Urine yellow? How is it formed?

Answer 22

1. Urobilin
2. Colonic Bacteria removes acid from Bilirubin converting it into Urobilinogen. Some of the Urobilinogen is recycled into the Portal System and the Liver puts it into the Systemic System where the blood filters and converts it into Urobilin