Review 7: Lipoproteins

Question 1

Where are chylomicrons formed?

Answer 1

small intestine

Question 2

Where are VLDL and HDLs?

Answer 2

in the liver

Question 3

what does Apo-CII do?

Answer 3

activates lipoprotein lipase (LPL) so tags and such can be broken down

Question 4

What does Apo E do?

Answer 4

it is a remnant receptor

Question 5

Chylomicrons are formed in the intestines along with Apo __ and Apo __

Answer 5

A-1 and B-48

Question 6

Chylomicrons gain Apo __ and Apo ____ from HDL in the plasma

Answer 6

E and C-II

Question 7

What is the function of LPL (lipoprotein lipase)?

Answer 7

converts TAGs to FFAs and glycerol

Question 8

How are chylomicron remnants removed once their contents have been broken down?

Answer 8

receptor-mediated endocytosis

Apo E binds to LDL receptor

Question 9

What is the source of Apo CII, Ai , and E?

Answer 9

HDL

Question 10

Chylomicrons transport __________ TAGs and cholesterol, VLDLs transport ___________ TAGs and cholesterol

Answer 10

exogenous (dietary); endogenous

Question 11

When do VLDLs turn into IDLs?

Answer 11

when they lose their TAG and shrink

Question 12

When do IDLs become LDLs?

Answer 12

when Apo C0II and Apo E are transferred to HDL

Question 13

How is LDL removed from circulation?

Answer 13

binding of Apo B-100 to the LDL receptor (found on hepatic and non hepatic tissue)

Question 14

What is the marker on LDL that is recognized by the LDL receptor?

Answer 14

Apo B-100

Question 15

What are the two ways LDL can be taken up by the cell?

Answer 15

1) receptor mediated (Apo B-100 binds to LDL receptor)

2) receptor independent (pinocytosed)

Question 16

When is receptor independent LDL uptake most important?

Answer 16

under conditions of high cholesterol (receptors are downregulated so this receptor independent pathway steps up to the plate)

Question 17

How is oxidation of LDL dangerous?

Answer 17

macrophages take up oxidized LDL and become foam cells which then accumulate, release cytokines that promote proliferation of smooth muscle cells and calcification of plaque

Question 18

Where are nascent HDLs synthesized?

Answer 18

liver and small intestine

Question 19

What is the marker on HDL that is recognized by the receptor?

Answer 19

Apo A-1

Question 20

What is the function of statins?

Answer 20

down regulate activity of HMG CoA-reductase so less cholesterol is produced – this upregulates LDL receptors which promotes removal of circulating cholesterol