Lipoprotein Metabolism

Question 1

2 places where lipids are synthesized

Answer 1

Liver and intestine

Question 2

How are triglycerides transported in plasma

Answer 2

Lipoproteins

Question 3

Classifications of the lipoproteins

Answer 3

All same components, just different %

Chylomicrons - most fat, least protein
HDL- least fat, most protein

HDL is smallest and most dense

Question 4

Give other names for the following

1. VLDL
2. LDL
3. HDL

Answer 4

1. Pre beta lipoprotein
2. Beta lipoprotein
3. Alpha lipoprotein

Question 5

What is an apoprotein

Function

Answer 5

Protein component of a lipoprotein

Mostly present on the surface; act as surface receptors

Question 6

Name where each of the following apoproteins are present:

1. Apo A-1
2. Apo B-48
3. Apo B-100
4. Apo C-II
5. Apo E

Answer 6

1. LCAT
2. Chylomicrons
3. VLDL and LDL
4. Lipoprotein lipase activator
5. IDL and chylomicrons

Question 7

Difference between structure of Apo B-48 and Apo B-100

Answer 7

They are both from the same B gene, 48 is only 48% transcribed and 100 is 100% transcribed

Question 8

List the lipoproteins in order of which has the highest cholesterol to lowest cholesterol

List them from highest TAG to lowest TAG

Answer 8

LDL, HDL, VLDL, chylomicrons

Chylomicrons, VLDL, LDL, HDL

Question 9

HDL

1. Generated by
2. Function

Answer 9

1. Liver and intestine

2. Delivers cholesterol to the liver for elimination

Question 10

LDL

1. Generated by
2. Function

Answer 10

1. VLDL

2. Deliver cholesterol to peripheral tissues

Question 11

VLDL

1. Generated by
2. Function

Answer 11

1. Liver

2. Deliver de novo TAG to peripheral tissues

Question 12

Chylomicrons

1. Generated by
2. Function

Answer 12

1. Intestine

2. Deliver dietary TAG to peripheral tissues

Question 13

How does an immature chylomicron become mature

What is the only component that an immature already has

Answer 13

Acquires Apo C-II and Apo E from HDL

Immature chylomicron has Apo B48

~immature VLDL has Apo 100 and also has to acquire apo C-II and apo E

Question 14

Immature chylomicrons are produced from

Answer 14

Dietary lipids

Question 15

Once chylomicron is mature it enters circulation where it is acted on by

Answer 15

Lipoprotein lipase (in muscle/adipose)

Question 16

Lipoprotein lipase converts chylomicron to chylomicron remnant. In this process, what does it release

Answer 16

Glycerol to liver (which can form DHAP), FFAs, and Apo C-II (which is returned back to HDL)

Question 17

What is required in order for packaging of lipoprotein

Answer 17

MTP

Question 18

When will serum be milky?

Answer 18

After a high fat meal, chylomicrons will temporarily cause serum to become milky

Question 19

Chylomicron remnant is taken up by liver by

Answer 19

Apo E receptors

Question 20

Lipoprotein lipase works on which lipoproteins

Answer 20

VLDL and chylomicrons

Question 21

If chylomicrons are still in your blood after not eating for ~5+ hours, what does that indicate

Answer 21

MTP or Apo B-48 are defective

Question 22

Lipoprotein lipase:

1. Converts chylomicrons to
2. Converts VLDL to

Answer 22

1. Chylomicron remnant

2. IDL

Question 23

What activates lipoprotein lipase

Answer 23

Apo C-II

Question 24

Chylomicrons

1. Assembled where?
2. Cholesterol or cholesterol ester
3. What type of apoprotein
4. Where does it go once synthesized

Answer 24

1. Intestinal mucosal cells
2. Cholesterol ester
3. Apo B48 and Apo E
4. Lymphatic circulation

Question 25

VLDL 1. Assembled where? 2. Cholesterol or cholesterol ester 3. What type of apoprotein 4. Where does it go once synthesized

Answer 25

1. Liver cells 2. Cholesterol 3. Apo B-100 (essential for removal of LDL) 4. Blood

Question 26

Main lipid component of both chylomicrons and VLDL

Answer 26

TAG

Question 27

Function of ACAT

Answer 27

Converts cholesterol to cholesterol ester

Question 28

1. Decreased cholesterol in the cell activates what two things? 2. Inhibits what?

Answer 28

1. LDL receptor gene expression, HMG CoA reductase 2. ACAT ~opposite for increased cholesterol in cells

Question 29

Deficiency of LDL receptor causes?

Answer 29

Increase in plasma LDL, thus an increase in plasma cholesterol (LDL receptor aids in cellular uptake/ degradation of LDL)

Question 30

When the pH of the endosomes (vesicles containing LDL) fall what happens to LDL? After this happens, what happens to the remnant of LDL?

Answer 30

LDL separates from its receptor-CURL Transferred to lysosome for degradation

Question 31

What happens to free cholesterol if it is not utilized?

Answer 31

It becomes esterified by ACAT and stored as cholesterol ester

Question 32

What is woolmans disease?

Answer 32

Inability to hydrolyse lysosomal cholesterol esters by cholesterol esterase

Question 33

What is Niemann-Pick disease?

Answer 33

Inability to transport unesterified cholesterol out of the lysosomes

Question 34

What is familial hypercholesterolemia (type II hyperlipidemia) what does it cause

Answer 34

LDL receptor deficiency (genetic or dietary); raises LDL level

Question 35

Name 3 enzymes activated by free cholesterol

Answer 35

ACAT, LCAT, and PCAT

Question 36

Function of scavenger receptor Class A (SR-A)

Answer 36

Endocytosis of chemically modified LDL in which lipid component or ApoB has been oxidized

Question 37

VLDL and CM require what two lipoproteins? Where do they get them from

Answer 37

Apo C-II and Apo E HDL

Question 38

Function of nascent HDL What enzyme functions to do this

Answer 38

Take up unesterified cholesterol and esterify them LCAT

Question 39

What activates LCAT activity

Answer 39

Apo A1

Question 40

What binds to HDL to facilitate uptake of cholesteryl esters? How does it bind to HDL

Answer 40

SR-B1 Via Apo A

Question 41

SR-B1 synthesis is upregulated for ?

Answer 41

Steroidogenesis

Question 42

LCAT 1. Bound to? 2. Function 3. What does it promote?

Answer 42

1. HDLs and LDLs in plasma 2. Esterifies cholesterol on surface of lipoprotein; cholesteryl ester moves to interior of lipoprotein 3. Flux of cholesterol from cell membranes into HDL

Question 43

HDL and IDL make an exchange. What is the exchange What is needed in order to make this exchange

Answer 43

HDL gives cholesteryl esters to IDL IDL gives TAG and phospholipids to HDL CETP

Question 44

Tangier disease: 1. Caused by 2. Will cause 3. How does it present

Answer 44

1. Defect in cholesterol transport out of cells; defects in ABC-A1 2. HDL levels will be half the normal amount 3. Build up of cholesterol in tonsils, liver, spleen, peripheral neurons; foam cells observed

Question 45

Type I Hyperlipidemia 1. Defect in? 2. Biochemical findings? 3. Features? 4. What will it not cause 5. Mortality from this is typically caused by

Answer 45

1. LPL or Apo C-II deficiency 2. Increased chylomicrons and increased TAG 3. Red/orange eruptive xanthomas, fatty liver/spleen, acute pancreatitis 4. Will not lead to atherosclerosis 5. Pancreatitis

Question 46

Type IIA Hyperlipidemia 1. Defect in? 2. Biochemical findings? 3. Features?

Answer 46

1. LDL receptor 2. Increased LDL and increased cholesterol 3. High risk of atherosclerosis, xanthomas of achilles tendon

Question 47

Type IV Hyperlipidemia 1. Defect in? 2. Biochemical findings? 3. Features?

Answer 47

1. Insulin deficiency 2. LPL will be inactive, increased TAG 3. Most common hyperlipidemia, associated with obesity, DM, and alcoholism

Question 48

Abetalipoproteinemia/Bassen-Kornzweig syndrome 1. Defect in which protein? 2. This protein is necessary for? 3. Deficiency leads to lack of 4. Characterized by

Answer 48

1. Microsomal triglyceride transfer protein gene; these synthesize of beta lipoproteins 2. Absorption of fat, cholesterol and ADEK 3. Apo B48 and Apo B100 4. Increased content of sphingomyelin and decreased content of lecithin