Lipid Transport

Question 1

Where are lipids transported to?

Answer 1

Gut -> Liver -> non hepatic tissue (inc. adipocytes) -> Liver

Question 2

What is the composition of fats and lipids in circulation?

Answer 2

Triacylglycerides - 45%
Cholesterol esters - 15%
Phospholipids - 35%
Free Fatty acids - 5%

Question 3

What are fatty acids made of?

Answer 3

Triglycerides

Question 4

Which factor alters the plasma composition?

Answer 4

Nutritional state

Question 5

What are the components of a lipoproteins?

Answer 5

• Phospholipids
• Cholesterol
• Cholesterol esters
• Triacylglycerides

Question 6

What is an apolipoprotein?

Answer 6

A protein that binds a lipid prosthetic group to form lipoproteins

Question 7

Fatty acids also help regulate thermogenesis, explain how?

Answer 7

Increase expression of UCP-2 and UCP-3 in mitochondria => increases thermogenesis

Question 8

Why can fatty acids not circulate the body unbound?

Answer 8

They would act as a detergent

Question 9

What is an apoprotein?

Answer 9

A protein that binds a prosthetic group to form a hormone or enzyme

Question 10

When does fatty acid saturation occur?

Answer 10

At about 2mM fatty acid molecules

Question 11

How are fatty acids stored?

Answer 11

In adipose tissues

Question 12

Why are different components significant?

Answer 12

Each component has a different function

Question 13

How are Lipoproteins transported?

Answer 13

Via blood as plasma lipoproteins

Question 14

How do fatty acids circulate the body?

Answer 14

Bound to a protein (albumin) as a Na+ salt

Question 15

What role do Fatty acids play energy metabolism?

Answer 15

Fatty acids (esp. polyunsaturated FA) are ligands for TFs involved in 
energy metabolism e.g. insulin metabolism regulation

Question 16

What is the role of Apolipoproteins?

Answer 16

Transport lipids through lymphatic and circulatory system

Question 17

How do dietary lipids enter circulation?

Answer 17

1. Triglycerides hydrolysed by lipases => FA + monoacylglycerides
2. Monoacylglycerides + FA transported across lumen membrane into
   Mucosal cell
3. Converted to triacylglycerides
4. Triacylglyceride -> chylomicrons + lipids + proteins
5. Chylomicrons enter lymphatic system

Question 18

List the apoproteins associated with the different Lipoproteins

Answer 18

• Chylomicrons: B48, APO C2, C3 and E
• VLDL: B100, apo C1, C2, C3 and E
• IDL: B100, APO E
• LDL: B100
• HDL: APO A1, A2, C1, C3, D and E

Question 19

How do Fatty acids regulate insulin metabolism?

Answer 19

• Upregulate lipid oxidation in liver and muscle

- Down regulate lippogenesis genes in liver and adipose tissues

Question 20

What is a common factor between the constsituents of the plasma?

Answer 20

They are all insoluble in water

Question 21

List the 5 types of lipoproteins

Answer 21

1. Chylomicrons
2. Very Low Density Lipoproteins (VLDL)
3. Intermediate Density Lipoproteins (IDL)
   - 4.Low Density LIpoproteins (LDL)
4. HIgh Density Lipoproteins (HDL)”

Question 22

What is the intracelluar concentration of fatty acids normally?

Answer 22

Conc. kept low

Question 23

What are the functions of apoproteins?

Answer 23

• Structure
• Solubilise lipids
• act as enzymes / cofactors
• tissue targetting

Question 24

How does VLDL acquire APO C and E?

Answer 24

VLDL made with only APO B100 apoprotein so acquires C and E from HDL as it circulates

Question 25

How do fatty acids enter cells?

Answer 25

By simple diffusion

Question 26

Where are the apoproteins added?

Answer 26

In the smooth endoplasmic reticulum

Question 27

Why do dietary lipids have a low density?

Answer 27

High Triglyceride concentration

Question 28

How are the chylomicrons secreted into the lymphatics?

Answer 28

secreted By enzyme reverse pinocytosis