Sesh 4- Lipid Transport

Question 1

What is the ideal level for plasma cholesterol?

Answer 1

<5mmol/L

Question 2

What are phospholipids classified according to?

Answer 2

Their polar, hydrophilic head

Question 3

Which enzyme converts cholesterol to cholesterol esters?

Answer 3

LCAT

Question 4

What 3 things make up the cargo of a lipoprotein?

Answer 4

1. Cholesterol esters
2. TAG
3. Fat soluble vitamins

Question 5

What is the lowest density class of lipoprotein?

Answer 5

Chylomicron

Question 6

What is the main lipoprotein class to transport dietary TAG?

Answer 6

Chylomicrons

Question 7

What is the main lipoprotein class to transport TAG made by the liver?

Answer 7

VLDL

Question 8

Which lipoprotein class has the largest diameter?

Answer 8

Chylomicrons

Question 9

Why are chylomicrons only in the blood 4-6 hours after a meal?

Answer 9

Because they only transport dietary TAG.

Question 10

What gives plasma a creamy appearance?

Answer 10

Presence of chylomicrons

Question 11

Which integral apolipoprotein is found in IDL, LDL and VLDL?

Answer 11

ApoB

Question 12

Which apolipoprotein is found in HDL?

Answer 12

ApoAI

Question 13

Which apolipoprotein is added to chylomicrons before they enter the lymph?

Answer 13

Apo B-48

Question 14

Which 2 apolipoproteins are added to chylomicrons once they are in the blood?

Answer 14

Apo C and E

Question 15

Which enzyme can Apo C on chylomicrons bind?

Answer 15

Lipoprotein lipase

Question 16

How are chylomicron remnants taken up by the liver?

Answer 16

• LDL R on hepatocytes binds Apo E on chylomicrons

- Chylomicrons then taken up by receptor-mediated endocytosis for lysosomal degradation

Question 17

Which enzyme is responsible for taking up TAG into cells, thereby reducing the TG content of lipoproteins?

Answer 17

Lipoprotein lipase

Question 18

What do LDL’s have a high content of?

Answer 18

Cholesterol

Question 19

Why aren’t LDL particles efficiently cleared by the liver?

Answer 19

LDL R’s in liver have a high affinity for Apo E, but LDL doesn’t contain ApoE

Question 20

Why is LDL more susceptible to oxidative damage than other lipoproteins?

Answer 20

Is not efficiently cleared by liver, so has longer half life

Question 21

What is the function of LDL?

Answer 21

Provides cholesterol synthesised by the liver to peripheral tissues.

Question 22

How is the expression of cell surface LDL receptors controlled?

Answer 22

By cell cholesterol concentration

Question 23

Which lipoprotein is responsible for reverse cholesterol transport?

Answer 23

HDL

Question 24

How does HDL reduce the likelihood of atherosclerotic plaque formation?

Answer 24

• Takes up excess cholesterol from endothelial cells lining blood vessels
• Therefore reduces chance of foam cell formation etc

Question 25

Why does a cholesterol-free diet not necessarily reduce plasma cholesterol levels?

Answer 25

Body can still synthesise cholesterol

Question 26

How do statins reduce plasma cholesterol concentrations?

Answer 26

Inhibit HMG CoA reductase- 1st enzyme in cholesterol synthesis pathway

Question 27

Define a hyperlipoproteinaemia

Answer 27

Any condition in which after a 12 hour fast, plasma cholesterol and/or triglyceride is raised.

Question 28

Why will patients with a defect in LCAT have unstable lipoproteins with an abnormal structure?

Answer 28

- No LCAT to convert surface lipid to core lipid | - Therefore cannot maintain the ratio of core to surface lipid which keeps lipoproteins spherical

Question 29

What is the function of HDL?

Answer 29

To transport cholesterol from cells which contain it excess to the liver or cells which require more cholesterol e.g. steroidogenic cells

Question 30

Name 3 signs that may be present in a patient with hypercholesterolaemia

Answer 30

1. Corneal arcus 2. Xanthelasma 3. Tendon xanthomas

Question 31

What are class IIa hyperlipoproteinaemias a defect in?

Answer 31

The LDL receptor

Question 32

Give examples of 2 types of drugs used to treat hyperlipoproteinaemias

Answer 32

1. Statins | 2. Bile acid sequestrants

Question 33

In a fasted sample, what is the ideal level of plasma triglyceride?

Answer 33

< 2mmol/L

Question 34

Which class of lipoprotein contains the most cholesterol?

Answer 34

LDL