Lipoprotein Physiology

Question 1

Describe the makeup of lipoprotein.

Answer 1

There is an apolipoprotein scaffold that holds cholesterol and triglycerides in the middle and has a phospholipid layer on the outside.

Question 2

List the types of lipoproteins from biggest to smallest.

Answer 2

Chylomicrons
VLDL
Remnant IDL
LDL
HDL

Question 3

List the ratio of triglyceride to ester in each of the lipoproteins.

Answer 3

Chylomicrons (10:1 triglycerides to cholesterol) 
VLDL (5:1)
Remnant IDL (1:1) 
LDL (1:~4)
HDL (1:~10)

Question 4

What are the types of lipoprotein found in each lipoprotein?

Answer 4

Chylomicron: B48
VLDL: B100
Remnant IDL: B? (not known)
LDL: B100 (because it is a downstream metabolite of VLDL)
HDL: A1

Question 5

Dietary fats are absorbed as ____________ and then __________.

Answer 5

broken up fatty acids (from lipase acting on triglycerides); get re-converted to triglycerides

Question 6

The purpose of chylomicrons is to _______________.

Answer 6

deliver dietary fats to peripheral tissues

Question 7

Liver makes fat and packages it as _________.

Answer 7

VLDL

Question 8

VLDL serves to _____________.

Answer 8

deliver liver-made fat to peripheral tissues

Question 9

_____________ hydrolyzes VLDL triglycerides and leaves LDL.

Answer 9

Lipoprotein lipase (in the capillary bed)

Question 10

LDL serves to _________________.

Answer 10

bring the unused triglycerides and cholesterol from VLDL back to the liver

Question 11

You can count how many __________ particles there are by counting B100.

Answer 11

VLDL and LDL

Question 12

Which part of the LDL molecule binds to hepatocytes?

Answer 12

B100

Question 13

How do statins decrease LDL?

Answer 13

They inhibit synthesis of hepatocyte cholesterol, causing the liver to get rid of more circulating LDL.

Question 14

The liver secretes ______ which picks up peripheral cholesterol and brings it back to the liver.

Answer 14

nascent disks (which is basically A1)

Question 15

What protein moves peripheral cholesterol to A1?

Answer 15

ABC A1 (adenosine-binding cassette A1)

Question 16

If you lack ______, you’ll have low circulating HDL due to inability to transfer peripheral cholesterol to HDL. This is a disease called Tangier’s and presents with orange tonsils and many peripheral cholesterol plaques.

Answer 16

ABC A1

Question 17

What does LCAT do?

Answer 17

Lecithin cholesterol acyl transferase transfers a fatty acid from a phospholipid to circulating cholesterol in HDL, creating cholesterol ester that is less soluble and therefore more likely to stick with the HDL particle on its route back to the liver.

Question 18

Cholesterol ester transfer protein swaps some _________ for ____________ when triglyceride levels are high. Low levels of this protein have been associated with high levels of HDL and decreased CVD events.

Answer 18

cholesterol ester from HDLs; triglycerides from VLDLs

Question 19

CETP results in the more rapid excretion of ________.

Answer 19

HDL, because triglyceride-laden HDL is more quickly excreted

Question 20

Apolipoproteins can also be enzymatic cofactors, such as ___________.

Answer 20

C2 (for lipoprotein lipase)

Question 21

Apolipoprotein E is a ligand for the __________ receptor.

Answer 21

remnant

Question 22

True or false: cholesterol must undergo additional phase I metabolism to be excreted renally.

Answer 22

False. Cholesterol has to be excreted in the bile as is.

Question 23

High triglyceride levels has been shown to cause ____________.

Answer 23

pancreatitis

Question 24

Dietary fats are broken down in the intestine by __________ before being absorbed by the intestinal villi and packaged into chylomicrons.

Answer 24

pancreatic lipase

Question 25

Why is it important to have people fast before measuring LDL and triglycerides?

Answer 25

Because dietary fat enters as chylomicrons and can skew the lab findings

Question 26

Apolipoproteins have ligands for what two things?

Answer 26

Lipoprotein lipase and liver receptors