Lipid Transport

Question 1

what are lipoproteins?

Answer 1

proteins that transport lipids through the bloodstream

Question 2

name 4 types of lipoproteins

Answer 2

1. chylomicrons
2. very low density lipoproteins (VLDLs)
3. low density lipoproteins (LDLs)
4. high density lipoproteins (HDLs)

Question 3

describe VLDLs

Answer 3

lots of lipid, low in protein

Question 4

describe LDLs

Answer 4

still lots of lipid, but more protein than VLDLs

Question 5

describe HDLs

Answer 5

high protein to lipid ratio

Question 6

what are apolipoproteins?

Answer 6

proteins associated with lipoproteins

Question 7

where are apolipoproteins location?

Answer 7

on the outside of lipoproteins

Question 8

what are the 3 functions of apolipoproteins?

Answer 8

1. structural
2. enzyme cofactors
3. ligands for receptors

Question 9

what is the function of VLDLs?

Answer 9

transport lipid from liver to other tissues

Question 10

what apolipoproteins to VLDLs contain? (2)

Answer 10

1. ApoB100

2. ApoE

Question 11

describe how VLDLs work (6)

Answer 11

1. enter bloodstream and associate with ApoCII
2. when ApoCII binds to lipoprotein lipase on capillary walls, TAG is broken down into FAs and glycerol
3. FAs enter tissue for energy and storage, glycerol goes to the liver
4. once approx 50% of TAG is removed, ApoCII dissociates and VLDL becomes IDL (intermediate density lipoprotein)
5. IDL allows for fat to diffuse into tissues via ApoE
6. once most of TAG has been removed, ApoE dissociates and IDL becomes LDL

Question 12

what must exist first in order to have LDLs?

Answer 12

VLDLs, to convert to IDLs to convert to LDLs

Question 13

what is the function of LDLs?

Answer 13

transport cholesterol

Question 14

describe how LDLs work (3)

Answer 14

1. LDL travels through bloodstream
2. when ApoB100 binds to receptors on capillary walls, cholesterol diffuses into tissues
3. once majority of cholesterol has been deposited throughout the body, LDL is removed from circulation via ApoB100 receptor on liver

Question 15

what do HDLs do?

Answer 15

transport cholesterol from tissues to the liver

Question 16

what apolipoprotein do HDLs contain?

Answer 16

contain ApoA-I

Question 17

describe how HDLs work (2)

Answer 17

1. enter bloodstream and remove cholesterol from tissue via ApoA-I receptors
2. eventually return to the liver and are removed from circulation via ApoA-I receptors

Question 18

what is the function of chylomicrons?

Answer 18

transport lipids from small intestine to other tissues

Question 19

what apolipoprotein do chylomicrons contain? what role does it play?

Answer 19

ApoB48; is structural and a ligand for receptors

Question 20

describe how chylomicrons work (6)

Answer 20

1. enter lymph from small intestine and travel to bloodstream
2. in the bloodstream, chylomicron associates with ApoCII
3. when ApoCII binds to lipoprotein lipase on capillary walls, the TAG in chylomicron is broken down into glycerol and 3 FAs
4. FAs enter tissue for energy and storage amd glycerol travels to the liver
5. once approx 80% of TAG is removed from chylomicron, ApoCII dissociates and now we have a chylomicron remnant
6. chylomicron remnant is removed from bloodstream by liver via ApoB48 receptor

Question 21

what are chylomicrons synthesized by?

Answer 21

the small intestine

Question 22

what are VLDLs synthesized by?

Answer 22

the liver

Question 23

what are LDLs synthesized by?

Answer 23

the liver

Question 24

what are HDLs synthesized by?

Answer 24

the liver