Lipoprotein Metabolism

Question 1

What are the 5 most important lipoproteins you should know?

Answer 1

chylomicron
vldl -very low density lipoprotein
hdl - high density lipoprotein
ldls - low density lipoprotein
idls - intermediate density lipoprotein

Question 2

what are apolipoproteins

Answer 2

proteins that bind to lipids to form lipoproteins

Question 3

Where is chylomicron secreted from and where does it go after secretion?

Answer 3

Chylomicron is secreted by intestine epithelial cells into the lymphatic system

Question 4

This enzyme activated by apo C II on circulating lipoprotein particles, hydrolyses the triglycerides into 3 fatty acids within chylomicrons. These free fatty acids are stored into the adipose tissues

Answer 4

Lipoprotein Lipase

Question 5

where is vldl secreted from?

Answer 5

liver

Question 6

where is vldl generated from?

Answer 6

hepatocytes

Question 7

VLDLs are composed of…. triglycerides than cholesterol

Answer 7

More

Question 8

List the names of the most dense lipoprotein to the least dense one?

Answer 8

HDLs (most dense)
LDLs
IDLs
VLDLs
Chylomicron remant
Chylomicron (least dense)

Question 9

What are 4 types of lipids present in lipoproteins

Answer 9

1. Cholesterol
2. Triglycerides
3. Phospholipids
4. Cholesterol esters

Question 10

Where are lipoproteins synthesised?

Answer 10

In the small intestine and the liver

Question 11

What do lipoproteins do?

Answer 11

They transport hydrophobic lipids such as cholesterol, triglycerides and phospholipids throughout the body

Question 12

Structure of lipoproteins

Answer 12

a hydrophobic core which contains: cholesterol esters and triglycerides

a hydrophilic shell containing: free cholesterol, phospholipids and hydrophilic proteins called apolipoproteins

Question 13

Where are chylomicrons secreted from?

Answer 13

Intestinal epilthelial cells

Question 14

Function of chylomicions

Answer 14

Transport dietary triglycerides from the intestine to peripheral tissues (adipose tissues, cardiac and skeletal muscle)

Question 15

What are chylomicion remnants?

Answer 15

Chylomicrons that are depleted of triglycerides

Question 16

What apolipoproteins are associated with chylomicrons?

Answer 16

ApoE, ApoC-ll (activates capillary lipoprotein lipase), Apo B48

Question 17

Function of VLDLs

Answer 17

Transports triglycerides from the liver to peripheral tissues

Question 18

How is VLDL converted into LDL

Answer 18

Hydrolysis of fatty acid by capillary lipoprotein lipase

Question 19

What apolipoproteins are associated with VLDLs?

Answer 19

ApoC-ll, ApoB-100,ApoE

Question 20

Degradation of…… forms IDL

Answer 20

VLDLs

Question 21

Function of IDLs

Answer 21

Transports triglycerides and cholesterol to the liver from peripheral tissues

Question 22

Apoplipoproteins associated with LDLs are…

Answer 22

ApoE, ApoB-100

Question 23

IDLs are composed of cholesterol and triglycerides at… amounts

Answer 23

Equal

Question 24

LDLs are composed of…. triglycerides than cholesterol

Answer 24

Less

Question 25

Function of chylomicronremnants

Answer 25

They transport cholesterol from peripheral tissues to the liver

Question 26

IDLs is converted into LDLs by what enzyme?

Answer 26

Hepatic lipase

Question 27

What happens to LDLs when it reaches its target cells?

Answer 27

It is endocytosis with LDL receptors and degraded leading to the release of cholesterol, decreasing further uptake of cholesterol

Question 28

ApoB-100 is the only apolipoprotein associated with this lipoprotein

Answer 28

LDLs

Question 29

Where are is HDLs secreted from?

Answer 29

Liver and Intestinal epithelium

Question 30

Function of HDLs?

Answer 30

Transports cholesterol from peripheral tissues (atherosclerotic arteries) to the liver, where it is excreted via bile

Question 31

Apolipoprotein's associated with HDLs

Answer 31

ApoE, ApoC-ll, ApoA-l

Question 32

What does ApoA-l do?

Answer 32

Activates LCAT to form cholesteryl esters

Question 33

What is the link between cholesteryl esters and ApoE and ApoC-ll

Answer 33

Cholesteryl esters help transfer these apolipoproteins to chylomicrons and VLDLs

Question 34

Where does the synthesis of apolipoproteins occur

Answer 34

In the rough endoplasmic reticulum and Golgi apparatus

Question 35

Name the 8 apolipoproteins you should know

Answer 35

ApoA-l ApoA-ll ApoB-48 ApoB-100 ApoC-l ApoC-ll ApoC-lll ApoE

Question 36

Function of ApoC-ll

Answer 36

Activates capillary lipoprotein lipase; releases fatty acids and glycerol from chylomicrons, VLDLs and IDLs

Question 37

A component of chylomicrons

Answer 37

ApoB-48

Question 38

Importance of ApoB-100

Answer 38

Contains B-48 domain and the LDL receptor recognition domain permitting binding to LDL receptors. Only structural Protein in LDL

Question 39

What are the 3 ways we can get some fat into our bloodstream? (detailed)

Answer 39

1. Diet The small intestine digests our food and packages the fat molecules, the triacylglycerides, into chylomicrons (protein carriers). Chylomicrons travel through our lymphatic system but eventually empty into our bloodstream, where they can enter capillary beds. 2. Adipose cells (specialised cells that can store large amounts of fats) Hormones such as glucagon signal adipose cells to release free fatty acids into the bloodstream 3. Liver Excess glucose can be converted into fatty acids, the liver packages these fatty acids into triacylglyceride molecules. These are packaged alongside cholesterol and other hydrophobic molecules into VLDLs, which eventually carry these to the capillary bed.