Digestion And Absorption Of Lipids

Question 1

What is the process of lipid digestion called?

Answer 1

Emulsification

Question 2

What is bile?

Answer 2

A shortened hydrocarbon chain synthesized in the liver

Question 3

How does cholic acid become glycocholic acid?

Answer 3

The acid is connected to the amino end of either glycine or taurine

Question 4

How are lipids degraded?

Answer 4

1. Colipase and lipase remove carbons 1 and 3 from TAG resulting in 2-monoglycerol and FFAs
2. Cholesteryl esters hydrolyzes into free cholesterol and FAs
3. Trypsin activates phospholipase-A2 to remove FA from carbon 2 of a phospholipid
4. Lysophospholipase removes remaining FAs from carbon 1

Question 5

How much cholesterol is esterified?

Answer 5

10-15%

Question 6

How is lipid digestion controlled?

Answer 6

1. CCK is released in response to lipids
2. Activates bile in the gallbladder and enzymes in the pancreas
3. Small intestine releases secretin in response to bile to neutralize pH

Question 7

How are lipids absorbed?

Answer 7

1. Micelles form as a cluster of degraded lipids
2. Micelles brush along the border of the intestinal membrane separated by unstirred water
3. Lipids are released from the micelle into the membrane

Question 8

How are lipids resynthesized?

Answer 8

1. All absorbed lipids travel to the endoplasmic reticulum
2. FAs convert to an active form by acetyl CoA synthetase
3. Acetyl CoA derivatives and 2-monoglycerol convert to TAGs by TAG synthase
4. Lysophospholipids form phosphates by acetyl CoA transferases
5. Cholesterol is esterified into FAs by cholesterol acyltransferase

Question 9

What happens if there is a pancreatic insufficiency?

Answer 9

Decrease in digestive enzymes and reduced nutrient absorption leading to polyphagia, weight loss, and loose stool.

Question 10

How is lipid digestion different in ruminants?

Answer 10

No emulsification or gastric lipase

Question 11

How are lipids digested in ruminants?

Answer 11

1. Microbial lipase hydrolyzes lipids and releases glycerol and FAs
2. Form propionic acid
3. Microbes convert unsaturated FAs to saturated FAs

Question 12

What is biohydrogenation?

Answer 12

Two groups of bacteria release linoleic and linolenic acid to alter the double bond positions and makes them more stable
Ex: stearic acid

Question 13

Is lipid absorption the same in non-ruminants and ruminants?

Answer 13

Yes