Plasma Lipoproteins

Question 1

Which two categories of lipoproteins contain the most TAG

Answer 1

Chylomicrons and VLDLs

Question 2

Order the lipoprotein’s lipid content from greatest to least

Answer 2

HDL>LDL>VLDL>Chylomicrons

Question 3

What composes the neutral lipid core of lipoproteins?

Answer 3

triacylglycerols and cholesterol esters

Question 4

What makes up the shell of lipoproteins?

Answer 4

Amphipathic apolipoproteins, phospholipids, and un-esterified cholesterol

Question 5

Order of lipoprotein density

Answer 5

HDL>LDL>VLDL>chylomicrons

Question 6

Order of lipoprotein size

Answer 6

Chylomicrons>VLDL>LDL>HDL

Question 7

Lipoproteins can be seperated by what two processes?

Answer 7

Ultracentrifugation and electrophoretic mobility

Question 8

Relative lipoprotein electrophoretic mobility

Answer 8

HDL>VLDL>LDL>Chylomicrons

Question 9

3 functions of apoplipoproteins

Answer 9

1) recognition sites for cell-surface receptors
2) Activators or coenzymes for lipoprotein enzymes
3) Lipoprotein structural component

Question 10

Apo A1 Function

Answer 10

Activates LCAT

Question 11

APO B48

Answer 11

loaded with lipids in intestinal mucosal cell to form chylomicron

Question 12

APO B100

Answer 12

LDL receptor ligand

Question 13

APO C-II

Answer 13

Activates lipoprotein lipase

Question 14

APO E

Answer 14

Binds receptor on liver for chylomicron remnants; also binds to LDL receptors

Question 15

Where are chylomicrons synthesized

Answer 15

intestinal mucosal cells

Question 16

Which apolipoprotein is specific to chylomicrons

Answer 16

APO B48

Question 17

Which form of APO B protein is intestine-specific?

Answer 17

APO B48

Question 18

The addition of which apolipoproteins are needed for nascent chylomicrons and nascent VLDLs to mature?

Answer 18

APO C-II and APO E

Question 19

What enzyme loads chylomicrons with additional lipids in the ER?

Answer 19

Triacylglycerol transfer protein

Question 20

In which tissues are enzyme concentrations of lipoprotein lipase the highest?

Answer 20

Heart endothelium, skeletal muscle, and adipose tissue

Question 21

What effect does insulin have on lipoprotein lipase?

Answer 21

Stimulates synthesis and the transfer of lipoprotein lipase to the luminal surface of capillary

Question 22

Which lipoprotein lipase isoenzyme has a low Km?

Answer 22

Heart lipoprotein lipase

Question 23

What lipoprotein donates and receives APO C-II to and from chylomicrons?

Answer 23

HDL

Question 24

How are chylomicron remnants recovered by the liver?

Answer 24

Liver cell lipoprotein receptors bind the APO E of the remnants

Question 25

Where are VLDLs synthesized?

Answer 25

Liver

Question 26

What is the primary content of VLDLs

Answer 26

Mostly triacylglycerol made in the liver for export to peripheral tissues

Question 27

How are LDLs made?

Answer 27

Mature VLDLs offload TAG and give up APO CII and APO E

Question 28

What proteins are passed from LDLs to HDLs?

Answer 28

APO C-II and APO E

Question 29

Action of Cholesterol ester transfer protein

Answer 29

Transfers TAG from VLDL to HDL and cholesterol esters from HDL to VLDL

Question 30

What is is caused by an APO E deficiency

Answer 30

Familial type III hyperlipoproteinemia

Question 31

Which type of lipoprotein has the highest level of cholesterol and cholesterol esters

Answer 31

LDLs

Question 32

Function of LDL

Answer 32

Provide cholesterol to peripheral tissues

Question 33

Which molecules do LDL receptors recognize

Answer 33

APO B100 and APO E

Question 34

What condition is caused by a deficiency in LDL receptors?

Answer 34

Type II hyperlipidemia

Question 35

What is the utility of the Compartment for Uncoupling of Receptor from Ligand

Answer 35

CURL is the compartment that separates and carries LDL receptors back to hepatic cell membrane after endocytosis and separation from LDL

Question 36

What are the effects of elevated intracellular cholesterol levels?

Answer 36

1) Inhbition of HMG CoA reductase 2) Decreases expression of LDL receptors 3) activates acyl CoA:cholesterol acyltransferase to store cholesterol as cholesterol esters

Question 37

What is the ligand for Scavenger receptor class A?

Answer 37

oxidized LDL

Question 38

What cell type expresses SR-A

Answer 38

macrophages

Question 39

What are foam cells?

Answer 39

Macrophages that have taken up a large amount of cholesterol

Question 40

What are the utilities of foam cells?

Answer 40

Their accumulation stimulates synthesis of cytokines and growth factors leading to inflammation and the growth of smooth muscle cells surrounding vessel epithelium to restrict flow. Additionally, they dump cholesterol which forms plaques to cut off blood flow to an area.

Question 41

How are HDLs formed?

Answer 41

APO A1 and lipids combine in the blood

Question 42

What is the function of HDL

Answer 42

1) Reservoir for apolipoproteins 2) Uptake of un-esterified cholesterol 3) Esterification of cholesterol 4) Reverse cholesterol transport

Question 43

How does a nascent HDL become mature

Answer 43

HDL takes up free cholesterol from other lipoprotein particles and cell membranes and becomes spheroid

Question 44

What are the different classifications of HDL as [CE] rises?

Answer 44

HDL--> HDL3--> HDL2

Question 45

What is the fate of HDL following the reception of TAG from VLDLs

Answer 45

It binds to Scavenger receptor B1 on surface of liver

Question 46

Why is HDL considered "good cholesterol"

Answer 46

It brings cholesterol fro, peripheral tissues to the liver, lowering peripheral cholesterol levels and lowering risk of atherosclerosis

Question 47

How is free cholesterol transported out of peripheral tissue cells?

Answer 47

ABCA1 transport protein

Question 48

Deficiency of ABCA1 leads to?

Answer 48

Tangier disease- absence of HDL