Lecture 2b-Lipoproteins

Question 1

Where are lipids derived from? and examples

Answer 1

• fatty acids
• e.g. fats, oils, waxes, steroids and sterols, hormones

Question 2

What is the function of lipids

Answer 2

• energy source
• component of cell membranes
• hormones-cell:cell communication
• insulation for nerves (sphingomyelins)
• Protection of and insulation for organs
• Vit A, D,E,K are lipid soluble
• Buoyancy

Question 3

why do lipids present a special challenge?

Answer 3

They are hydrophobic

Question 4

Fatty acids make up….

Answer 4

cholesterol and triacylglycerols (Fats, triglycerides)

Question 5

Cholesterol makes hormone that we need for _____ _____

Answer 5

dietary needs

Question 6

Triacylglycerols are used for?

Answer 6

for energy

Question 7

What transports lipids

Answer 7

lipoproteins

Question 8

What is the composition of a lipoprotein

Answer 8

• inside: core containing triacylglycerols and cholesteryl esters
• Outside: phospholipids, cholesterols, apolipoproteins (binds lipid to proteins to be transported)

Question 9

Part two of anatomy of lipoprotein

Answer 9

Core: nonpolar lipids
* cholesterol ester
* triglyceride

Outside: amphipathic lipids
* phopholipid
* cholesterol

Question 10

What does cholesterol do?

Answer 10

Prevents it from collapsing

Question 11

name the lipoproteins from highest to lowest density

Answer 11

HDL, LDL,IDL, VLDL, chylomicrons

Question 12

Which lipoprotein has the most triacylglyerols

Answer 12

chylomicron which also has the least cholesterol

Question 13

Which lipoprotein has the most cholesterol

Answer 13

LDL

Question 14

The more triacylglycerols, what happens to size of lipoprotein

Answer 14

it gets bigger

Question 15

As density increases, the size

Answer 15

decreases

Question 16

what are apoprotiens

Answer 16

are on the surface, providing structure and function (binding and enzyme activation

Question 17

Apo A-I is associated with what lipoprotein and what is the function

Answer 17

• HDL
• Structural protein for HDL and activator of LCAT

Question 18

Apo B-100 is associated with what lipoprotein and what is the function

Answer 18

• VLDL, IDL, LDL
• structural protein for VLDL and LDL and ligand for binding to LDL receptor

Question 19

Apo B-48 is associated with what lipoprotein and what is the function

Answer 19

• Chylomicrons
• Structural proteins for chylomicrons

Question 20

ApoA-1 is unique to what

Answer 20

to HDL–> structural and enzyme activator

Question 21

ApoB is unique to what?

Answer 21

to non-HDL particles–> structural and ligand for receptor binding

Question 22

how do we change apolipoproteins B?

Answer 22

mRNA editing

Question 23

What happens to the apolipoprotein B in the intestine

Answer 23

• There is cytidine demainase editing complex (active) which changes CAA to UAA (stop codon) so we get 48

Question 24

What happens to the apolipoprotein B in the liver

Answer 24

The codon stays as a Gln (CAA) and becomes a apoB100 proteins

Question 25

apoB 48 is expressed in what and involved in what ?

Answer 25

Expressed mucosal cells and involved in receptor mediated chylomicron by the liver

Question 26

apoB 100 is expressed in what and involved in what ?

Answer 26

expressed in the liver and involved in receptor mediated LDL uptake by the liver

Question 27

explain the process of chylomicrons

Answer 27

Question 28

Lipoprotein lipase (LPL) reaction

Answer 28

Question 29

lipoprotein lipase present in:

Answer 29

* adipocytes * striated mucsles * prancreatic islets * macrophages

Question 30

What is the fuction of lipoprotein lipase

Answer 30

Hydrolysis of TG presents hydrolysis of TG present in chylomicrons and very-low density lipoproteins

Question 31

what is the substrate for LPL reaction

Answer 31

triacylglycerol

Question 32

What are the products of the lipoprotein lipase reaction

Answer 32

1,2-diacylglycerol and fatty acid

Question 33

explain how VLDL and LDL are interconnected

Answer 33

Question 34

What is the subtrate for lipoprotein

Answer 34

triglycerol

Question 35

What is the LCAT reaction

Answer 35

Question 36

What substrate can be used besides lecitin ?

Answer 36

Acyl-coenzyme:cholesterol actltransferases (ACAT)

Question 37

what lipoprotein does reverse cholesterol transport?

Answer 37

HDL particles

Question 38

What does HDL do

Answer 38

Question 39

What is the function of HDL and LDL

Answer 39

* **HDL**: reverse cholesterol transport back to the liver for excretion * **LDL**: takes cholesterol to all different organs

Question 40

Explain the interconnecions of CETP (cholesterol ester transfer protein

Answer 40

Question 41

Overview of HDL particles-reverse cholesterol transport

Answer 41

* HDL removes cholesterol from tissue and transports it to liver * liver disposes cholesterol as bile acids * HDL is called "good" cholesterol

Question 42

What happens when cholesterol is taken up via LDL receptors

Answer 42

* LDL is internalized, then lysomoal hydrolysis to relaease cholesterol * Once you have enough cholesterol in the cell regulatory actions: 1. **decrease** HMG CoA reductase (enzyme that makes cholesterol 2. **increase** ACAT or LCAT (makes cholesterol esters 3. **decrease** LDL receptors (no more cholesterol taken up

Question 43

Where are chylomicrons synthesis in, secreted into, contains, rich in and function

Answer 43

* **Synthesis** in: The small intestines in the fed state * **Secreted** into: the lymph vessels, then---> moves into the blood * Contains **apo B48** * **Rich** in:TGs * **Function**: deliver TG's to body cells to be used as fuel

Question 44

Where are VLDL synthesis in, secreted into, contains, rich in and function

Answer 44

* **Synthesis** in the liver from excess dietary carbohydrate and protein along with the Chylomicron remnant * **Secreted** into: the bloodstream * **Rich** in: TGs * **Function**: Deliver TGs to body cells * Contains **apo B100**

Question 45

Where are LDL synthesis in, secreted into, results from, rich in and function

Answer 45

* **Synthesis** in the Liver as VLDL * **Results** from: VLDL once it has lost a lot of its TG’s and C-->CE * **Secreted** into: the bloodstream * **Rich** in: Cholesterol * **Function**: Deliver cholesterol to all body cells

Question 46

Where are HDL synthesis in, secreted into, results from, rich in and function

Answer 46

* **Synthesis** in : the Liver and Small Intestine * **Secreted** into: the bloodstream * **Function**: Pick up cholesterol from body cells and take it back to the liver = “reverse cholesterol transport” * Potential to help reverse heart disease

Question 47

What does hyperlipidemia/hyperlipoproteinemia cause

Answer 47

Increase risk of atherosclerosis and cardiovascular diseases

Question 48

What is familial hypercholesterolemia

Answer 48

* FH patients have high LDL and plasma cholesterol levels * Lack LDL receptors: decrease degradation of LDL * Mutations in LDL receptor gene

Question 49

What is are the souces of cholesterol

Answer 49

found in aminal food only

Question 50

Where is cholesterol synthesized ?

Answer 50

Liver

Question 51

What is the atherosclerosis: LDL hypthesis?

Answer 51

* Elevated levels of LDL cholesterol and apoB100 directly contribute to atherosclerosis * Oxygen radicals in endothelial lining of the arteries oxidize LDL and retain them * Activated endothelial cells have increased inflammation * Macrophages take up LDL and are saturated with cholesterol thus forming foam cells

Question 52

What are the major enzymes of lipoprotein metabolism:

Answer 52

* Lipase (LPL) * Lecithin:Cholesterol Acyl Transferase (LCAT) * Cholesterol ester transfer Protein (CETP)