Week 3 Lipoproteins Apolipoproteins in Lipid Metabolism

Question 1

What is the function of plasma Lipoproteins?

Answer 1

• their function is in the transport of lipids in the plasma

Question 2

What types of molecules do plasma lipoproteins contain?

Answer 2

hydrophobic, hydrophilic, amphipathic molecules, also contain proteins (apolipoproteins)

Question 3

What do lipoproteins do?

Answer 3

They keep lipids soluble and they transport lipids to and from various tissues

Question 4

What are the 4 different types of plasma lipoproteins

Answer 4

• chylomicron (more TAG)
• VLDL (Less TAG)
• LDL (Less TAG)
• HDL (Lowest TAG)

Question 5

What is the role of the chylomicron?

Answer 5

to transport TAG from the intestines to the peripheral tissues

Question 6

What does lipoprotein destination depend on?

Answer 6

Their apolipoproteins

Question 7

What is the role of apolipoproteins?

Answer 7

• recognition sites
• activators or coenzymes for enzymes
• structural

Question 8

Assembly of amino acid B-48 requires?

Answer 8

MTP; ER/Golgi, chylomicron

Question 9

When are new chylomicrons rapidly modified?

Answer 9

Once they reach the plasma

Question 10

The addition of apoE and apoC-II leads to?

Answer 10

Recognition by hepatic receptors and activation of lipoprotein lipase (degrades the TAGs present in the chylomicron)

Question 11

What stimulates lipoprotein synthesis and transfer to luminal surface of capillary?

Answer 11

Insulin

Question 12

What do different TAGs have that help differentiate their different tissue-specific isoforms?

Answer 12

Km values for TAG

Question 13

What happens when 90% of the TAGs are removed?

Answer 13

The chylomicron remnants return to the liver and are endocytosed and are degraded by the lysosome.

Question 14

What is lipoprotein lipase activated by?

Answer 14

ApoCIII, stimulated by insulin

Question 15

What does lipoprotein lipase do?

Answer 15

It causes the release of fatty acids and glycerol from TAGs in lipoproteins.

Question 16

What the different LIPID transfer proteins?

Answer 16

HTGL
LCAT
CETP

Question 17

What is the role of CETP?

Answer 17

Facilitates the exchange of cholesteryl esters for TAGs between HDL, VLDL and IDL, contributing to reverse cholesterol transport

Question 18

What does cholesterol transported by lipoprotein back up?

Answer 18

It backs up the capacity of cells to synthesise cholesterol

Question 19

What are the main stages of lipoprotein metabolism?

Answer 19

• assembly of lipoprotein particles (chylomicrons in the intestine)
• transfer of lipoprotein to peripheral cells (release of TAGs/FA from lipoproteins to cells)
• liver uptake
• generation of LDL particles
• reverse cholesterol transport

Question 20

What are the 4 different types of apolipoproteins?

Answer 20

A, B, C, D, E (E1-4)

Question 21

Individuals with E4 isoform are shown to be at an increased risk of a sporadic form of what?

Answer 21

Alzheimer Disease

Question 22

What is the LDL receptor apoE/B regulated by?

Answer 22

Intracellular cholesterol concentration

Question 23

What are scavenger lipoprotein receptors?

Answer 23

Nonspecific and nonregulated

Question 24

What are the 3 functions of the liver?

Answer 24

Endocrine and exocrine

Question 25

Food entering the duodenum stimulates the secretion of cholecystokinin and this is turn stimulates?

Answer 25

pancreatic enzyme production and secretion (bile release)

Question 26

The acidity of the stomach contents entering the duodenum stimulates the release of secretin, what does this do?

Answer 26

It triggers the secretion of bicarbonate rich pancreatic fluid, which neutralises the acidity in the duodenum.

Question 27

What is the most important biochemical marker present in pancreatitis?

Answer 27

Increased amylase activity in serum

Question 28

What is chronic pancreatitis a consequence of?

Answer 28

Long term inflammation and leads to malnutrition and steatorrhea

Question 29

Zollinger Ellison is a rare disorder involving what?

Answer 29

The chylomicron assembly being impaired.

Question 30

In cystic fibrosis, which regulator protein is affected?

Answer 30

CF transmembrane conductance regulator protein

Question 31

What is the treatment for cystic fibrosis?

Answer 31

Lipase enzyme replacement and vitamin supplementation

Question 32

Where are VLDLs produced?

Answer 32

In the liver

Question 33

What is the role of VLDL?

Answer 33

To provide cholesterol to peripheral tissues en route to the liver

Question 34

What is atherosclerosis?

Answer 34

The hardening of the arteries.

Question 35

What is the link between LDL and atherosclerosis?

Answer 35

LDL usually enters cells by receptor mediated endocytosis
Scavengers are not turned off with high cholesterol… uptake of oxidized LDL.. convert to foam cells
Foam cells contribute to plaque formation.

Question 36

What is reverse cholesterol transport?

Answer 36

This is where direct HDL transport of cholesterol esters to the liver. Remnants is not taken up but sent back out to scavenge cholesterol and exchange apolipoprotein and TAG.

Question 37

Familial Hypercholesterolemia involves? Which receptor?

Answer 37

The defect makes the body unable to remove LDL cholesterol from the blood. This results in high levels of LDL in the blood.
PCSK9 receptor

Question 38

What does NAFLD involve?

Answer 38

deposition of excess TGs in the liver

Question 39

What type of disease is Wolmans Disease and what is the deficiency?

Answer 39

Lysosomal acid lipase deficiency - certain fats may abnormally accumulate in the tissues and organs of the body.
Genetic - autosomal recessive - mutations