Lipid Transport

Question 1

How are lipids transported in plasma?

Answer 1

As lipoproteins

Question 2

What does a lipoprotein consist of?

Answer 2

Lipid core + single surface layer of: amphipathic phospholipid, cholesterol, and apoprotein (protein moiety)

Question 3

How are lipoproteins separated into chemical classes? What are the 5 apoprotein names?

Answer 3

Ultracentrifugation; A, B48, B100, C, E

Question 4

What is the location + function of apoprotein A?

Answer 4

HDL; activator for enzyme LCAT (lecithin cholesterol acyl transferase)

Question 5

What is the location + function of apoprotein B48?

Answer 5

Chylomicron; ligand

Question 6

What is the location + function of apoprotein B100?

Answer 6

VLDL/LDL; ligand

Question 7

What is the location + function of apoprotein C?

Answer 7

HDL; structural

Question 8

What is the location + function of apoprotein E?

Answer 8

HDL, ligand

Question 9

What is the largest lipoprotein? What is it’s density? How is it transported?

Answer 9

Chylomicron, least dense, Dietary fats aka EXOGENOUS lipids

Question 10

Explain the clearance and reuptake of Chylomicrons

Answer 10

Clearance from blood is rapid
Liver reuptakes via receptor mediated endocytosis

Question 11

What is the 2nd largest lipoprotein? What is it’s density? How is it transported?

Answer 11

VLDL, ENDOGENOUS lipids made in liver - mainly TAG and some CEs (cholesterol esters)

Question 12

How do VLDL FAs enter tissue (especially adipose)?

Answer 12

Lipoprotein lipase in cell walls of capillaries allow FAs to enter tissues

Question 13

What is the 3rd largest lipoprotein? What is it’s density? How is it formed?

Answer 13

LDL, after the action of lipoprotein lipase on VLDL, LDL is formed - mainly CEs

Question 14

What moves into tissue when LDL binds to B100 receptors in what location?

Answer 14

CE, B100 receptors in arterial SmM cells, fibroblasts, and macrophages

Question 15

What is the smallest lipoprotein? What is it’s density? How is it transported? What is this transport called?

Answer 15

HDL; mainly protein carries cholesterol BACK to liver: Reverse Cholesterol transport

Question 16

In reverse cholesterol transport, where is nascent HDL (discoidal) synthesized?

Answer 16

Liver

Question 17

What is the 2nd step of reverse cholesterol transport? What enzyme is involved and what is the action of this enzyme? What happens to the products of this enzyme’s action?

Answer 17

DIscoidal HDL (hockey puck) uptakes + esterfies cholesterol from tissue, becoming HDL3 (baseball); LCAT converts free cholesterol into esters + lysolecithin: CEs move into HDL core + Lysolecithin is transferred to albumin

Question 18

In the 3rd step of Reverse cholesterol transport, what happens to HDL3?

Answer 18

Becomes bigger + less dense = HDL2 (basketball)

Question 19

In the 4th step of Reverse cholesterol transport, what happens to HDL2? What enzyme?

Answer 19

Hepatic lipase allows cholesterol + CEs to unload in liver, forming HDL3

Question 20

In the 5th step of Reverse cholesterol transport, what happens to HDL3?

Answer 20

HDL3 reenters circulation

Question 21

What is the impact of sex hormones on Hepatic Lipase?

Answer 21

Increased by androgens (testosterones) = lower HDL in men
Decreased by estrogens = ^HDL in menstruating women

Question 22

What does ^levels HDL do?

Answer 22

Reduce risk of atherosclerosis

Question 23

What factors ^HDL?

Answer 23

Reduced refine carb diets, ^action of lipoprotein lipase (exercise), estrogen (pre-menopausal women)