Lipoproteins 1

Question 1

What is a apolipoprotein?

Answer 1

Enzyme activator involved in lipid metabolism, act has a ligand for various tissues (at least 10 exist)

Question 2

What types of lipoproteins are Exogenous?

Answer 2

Chylomicrons

Question 3

What types of lipoproteins are Endogenous?

Answer 3

VLDLs, LDLs, IDLs, HDLs

Question 4

What is the main source of fat in the North American diet?

Answer 4

Triglycerides (95%) - 100-150 grams/day

Question 5

Why is pure rapeseed oil not good to use?

Answer 5

Very rich in erucic acid (omega 9) which is considered toxic

Question 6

The non-GMO strain of rapeseed (00) is called what? Why is it safe?

Answer 6

Canola oil, greatly reduced in erucic acid

Question 7

What type of fats increase cholesterol?

Answer 7

Trans and saturated

Question 8

What do lipoprotein lipases do?

Answer 8

Chop us fatty acids (FAs) off Triacylglycerides (TAGs)

Question 9

What are chylomicrons?

Answer 9

Large, least dense lipoproteins that takes lipids from the intestine and takes TAGs to deliver them to the blood vessel wall
Takes the rest towards the liver

Question 10

What are micelles composed of?

Answer 10

Bile salts and phopholipids - much smaller than fat globules

Question 11

What does it mean when fatty acids and micelles are partitioned across the water layer?

Answer 11

Passively diffused uptake based oh concentration of FA in cell

Question 12

Why is cholesterol harder to absorb into the cell?

Answer 12

It is esterified - harder to make into micelles

Question 13

Where are chylomicrons assembled in the enterocyte?

Answer 13

ER

Question 14

Fatty acids are reassembled in the ____ into ____ by ___.

Answer 14

ER, TAGs, apoproteins

Question 15

Which apoprotein activates Lipoprotein lipase (LPL)?

Answer 15

APO-CII

Question 16

How do LPLs do with chylomicrons? What is the process called?

Answer 16

LPLs hydrolyze them, then release free FAs (by digesting TAGs) into cells
Exogenous transport system

Question 17

What is done with the left over chylomicrons?

Answer 17

They are taken up by endocytosis into the liver
The chylomicrons also take some cholesterol esters with them
Also carry lipid soluble vitamins (A, D, E, K)

Question 18

What does the liver do when there its more fat uptake than it need? What is the process?

Answer 18

Excess FA is converted into TAGs and packaged into VLDLs which are secreted via the Endogenous transport system
APO-CII activates LPL which hydrolyzes TAGs to release free FAs for cell uptake - makes fuel, milk or is stored

Question 19

What happens to leftover VLDLs?

Answer 19

They still have apoE so 50% are taken up by the liver

Question 20

How are LDLs formed?

Answer 20

By the other half of non-absorbed VLDLs with their TAGs removed by hepatic lipase

Question 21

LDLs are higher in:

Answer 21

Cholesterol and cholesterol esters

Question 22

60% of LDLs bind to apoB-100 and taken to the liver. What happens to the rest?

Answer 22

Goes to cells (adrenocortical/gonadal) to make steroid hormones
Also needed for membrane fluidly and vit D synth

Question 23

What are 3 ways HDLs can be made?

Answer 23

De novo synthesized by liver and intestine (ER)
Generated from chylomircon and VLDL remnants
Apoprotein Al will acquire phospholipids and cholesterol

Question 24

How does HDL prevent cholesterol from flipping HDL into the outter leaf of a cell membrane so that cholesterol can’t be picked up?

Answer 24

It uses Lecithin: Cholesterol acyltransferase (LCAT)

Question 25

What is the main action of LDL?

Answer 25

Its the main cholesterol transporter delivering cholesterol to blood vessel wall and liver

Question 26

What is the main action of HDL?

Answer 26

Removed cholesterol from blood vessel wall and transport cholesterol ester to LDLs

Question 27

What is the main action of VLDL?

Answer 27

Transport triglycerides and cholesterol from liver and deliver them to blood vessel walls