Lipoprotein Metabolism Flashcards
1
Q
what are lipoproteins
A
- transport vehicles for triglycerides, phospholipids, cholesterol, and cholesterol esters
2
Q
what do lipoproteins work with?
A
- apoproteins
3
Q
lipoproteins consist of
A
- central core
- surface monolayer
4
Q
central core composed of
A
- triglycerides
- cholesterol esters
5
Q
surface monolayer composed of
A
- phospholipids
- proteins
- cholesterol
6
Q
plasma lipoproteins classified by density from least dense to most dense
A
- chylomicrons
- VLDL (remnants of IDL)
- LDL
- HDL
7
Q
exogenous pathway
A
- dietary lipids from intestine -> peripheral tissue and liver
8
Q
endogenous pathway
A
- synthesized lipids from liver -> peripheral tissue
9
Q
reverse cholesterol transport pathway
A
- cholesterol from peripheral tissue -> liver
10
Q
role of apo C
A
- activator of lipoprotein lipase
11
Q
role of apo A
A
- binding of HDL to peripheral tissues
- activator of LCAT
12
Q
role of apoB-100
A
- binding of LDL to LDL receptor
13
Q
role of apo E
A
- binding of chylomicron, VLDL, and HDL remnants to the liver after their TGs have been removed
14
Q
role of apoB plus apoE
A
- binding of IDL to the liver
15
Q
lipoprotein lipase located on
A
- endothelial surface of blood capillaries adjacent to tissues capable of using fats
16
Q
lipoprotein lipase required for
A
- TG hydrolysis from chylomicrons and VLDL
17
Q
lipoprotein lipase activated by
A
- apoC
- insulin
18
Q
hepatic lipase located on
A
- endothelial surface of blood capillaries adjacent to the liver
19
Q
role of hepatic lipase
A
- hydrolyzes TGs in final stage of conversion of VLDL, IDL, and LDL
- removal of cholesterol during final stages of HDL metabolism
20
Q
regulation of hepatic lipase
A
- not regulated
21
Q
removal of triglycerides primarily catalyzed by
A
- lipoprotein lipase
22
Q
removal of triglycerides yields
A
- remnant particles
23
Q
remnant particles targeted to
A
- liver for destruction
24
Q
where can cholesterol diffuse
A
- among lipoproteins and between lipoproteins and tissue
25
until cholesterol esters are esterified, where do they remain
- with lipoproteins
26
what can lipoprotein particles exchange with each other
- apoproteins
- cholesterol
- cholesterol esters
- phospholipids
27
role of HDL
- important acceptor and donor
28
exogenous pathway - chylomicrons synthesized by
- intestinal mucosal cells with apoA and apoB48
29
exogenous pathway - chylomicrons pick up
- apoC, poE, and CE from HDL
30
exogenous pathway - because chylmicrons have apoC now, what can they do?
- bind to LPL at muscle and adipose and TG
| - release free fatty acids
31
exogenous pathway - after triglyceride is removed
- apoA and apoC transferred to HDL
| - leaves chylomicron remnant
32
exogenous pathway - chylomicron remnant taken up by
- liver via apoE receptors
33
half life of chylomicron remnant
- very short (minutes)
34
endogenous pathway (triglycerides) - VLDL synthesized
- in liver with TG, CE, C, and apoB 100
| - in the fed state
35
endogenous pathway (triglycerides) - VLDL then obtains
- apoE and apoC from HDL
36
endogenous pathway (triglycerides) - apoC->LPL
- hydrolyzes TGs to FFA in muscle and adipose
| - then picks up CE and transfers apoC to HDL
37
endogenous pathway (triglycerides) - after TG removed and apoC lost of HDL
- becomes remnant particle called IDL
38
two classes of IDL
- rich in apoE
| - low in apoE
39
particles that are rich in apoE
what kind of process is this?
- binds to apoE and apoB receptors in liver and is destroyed
| - this is a rapid process (hours)
40
endogenous pathway (cholesterol) - remnant IDL with little apoE what happens
- loses TG to hepatic lipase
- converted to LDL
- LDL also picks up CE from HDL
41
LDL then loses cholesterol to
- peripheral tissues by passive diffusion
| - and binding to apoB receptor
42
LDL eventually binds to
how long does this process take?
- apoB receptor in liver
- internalized and destroyed
- this process takes days
43
role of chylomicrons and VLDL
- transport triglycerides and cholesterol to the peripheral tissue
44
what happens apoC binds to LPL at the muscle and adipose tissue
- removal of triglycerides
45
what does the removal triglycerides caused
- remnant particle
| - guided to liver by apoB
46
clearance rate of the apoE-low LDL
- cleared very slowly
47
role of LCAT
- esterifies cholesterol associated with HDL
| - traps cholesterol in the interior of the HDL particle
48
what activates LCAT
- apoA
49
role of CETP
- transfers cholesterol esters from HDL to VLDL, IDL, and LDL
- main mechanism for delivery of cholesterol to the liver
50
CEPTP with PLTP
- transfers triglycerides and phospholipids from particles to HDL
51
role of Apoprotein A
- facilitates binding of HDL particles to ApoA receptors on peripheral tissues
- activates transport protein called ABC1
- activates LCAT reaction
52
role of ABC1
- responsible for efflux of cholesterol from peripheral tissue
53
Reverse cholesterol transport - nascent HDL synthesized by
- liver and intestine with ApoA and apoE
54
Reverse cholesterol transport - HDL picks up
- apoA and apoC from VLDL remnants and chylomicron remnants
55
Reverse cholesterol transport HDL then donates
- apoC and apoE to chylomicrons
56
Reverse cholesterol transport - nascent HDL then binds to
- apoA receptor on peripheral tissue
| - picks up cholesterol
57
Reverse cholesterol transport - HDL particles contain
- LCAT
| - CETP
58
Reverse cholesterol transport - VLDL, IDL, and LDL bind to
- receptors on liver
| - internalized and destroyed
59
Reverse cholesterol transport - HDL finally binds to
- apoE receptors on the liver
| - internalized and destroyed
