Flipped Classroom: Lipoproteins II Flashcards
(100 cards)
1
Q
Successively denser, having higher ratios of protein to lipid and therefore will be on top of the centrifuge tube
A
VLDLs and LDLs
2
Q
Can also be separated on the basis of their size using electrophoretic mobility
A
Plasma lipoproteins
3
Q
Function in the regulation of lipoprotein metabolism through their involvement in the transport and redistribution of lipids among various cells and tissues
A
Apoproteins
4
Q
Have a role as cofactors for enzymes of lipid metabolism
A
Apoproteins
5
Q
Apoproteins help maintian the structure of
A
Lipoproteins
6
Q
What are the two basic phases of lipoprotein metabolism?
A
Processing and clearance
7
Q
When lipoproteins undergo changes in composition of both surface and core components
A
Processing phase
8
Q
Cleared from the blood via reeptor-mediated endocytosis (clearance phase)
A
Lipoproteins
9
Q
Major protein of HDL
-activates LCAT
A
ApoA-I
10
Q
Primarily found in HDL where it activates hepatic lipase activity
A
ApoA-II
11
Q
Derived from ApoB-100 gene by RNA editing
-Found exclusively in chylomicrons
A
ApoB-48
12
Q
ApoB-48 lack the
A
LDLR binding domain
13
Q
Major protein of LDL
-Binds to LDL receptor (LDLR)
A
ApoB-100
14
Q
Activates lipoprotein lipase (LPL)
A
ApoC-II
15
Q
Inhibits LPL
A
ApoC-III
16
Q
Major protein of remnant lipoproteins
A
ApoE
17
Q
ApoE binds to
A
LRP and LDLR
18
Q
What are the two important lipases in lipoprotein metabolism
A
Lipoprotein lipase and hepatic lipase
19
Q
Hydrolyze triglycerides into FFAs and glycerol
A
LPL and Hepatic lipase
20
Q
Attached by interaction with glycosaminoglycans on the endothelial cells
A
Lipoprotein Lipase (LPL)
21
Q
Interacts with chylomicrons or VLDLs to catalyze the hydrolysis of triacylglycerides to FFAs and glycerol
A
LPL
22
Q
Serves as a cofactor for LPL on the lipoprotein
A
ApoC-II
23
Q
What percentage of the FFAs are taken by adipose tissue, heart, and muscle?
-rest returned to liver
A
80%
24
Q
Primarily a phospholipase, but also possesses triglyceride hydrolase activity
A
Hepatic Lipase (HL)
25
HL is synthesized by hepatocytes and is present primarily on
Liver endothelial cells
26
Transported from the liver to the capillary endothelium of the adrenals, ovaries, and testes, where it functions in the release of lipids from lipoproteins for use in these organs
HL
27
Serves as the cofactor for HL on HDL
ApoA-II
28
Hydrolyzes triglycerides and possibly excess surface phospholipids in the final processing of chylomicron remnants
HL
29
HL completes the processing of IDL to
LDL
30
Participates in the conversion of HDL2 to HDL3 by the removal of triglyceride and phospholipid from
HDL2
31
Important for metabolizing dietary triacylglycerols and contain B48, CII, CIII, and E
Chylomicrons
32
Important for metabolizing liver derived triacylglycerols and contain B100 instead of B48
-also contain CII, CIII, and E
VLDLs
33
Formed in cicrulation by VLDL metabolism and delivers primarily cholesterol to the peripheral tissues
LDL
34
Contains only B100
LDL
35
Synthesized in the liver and reside on HDL
ApoC-II and III
36
Mainly stems from the liver, and chylomicrons acquire it from HDL
ApoE
37
Lipoprotein metabolism can be broken down into which three pathways?
1. ) Exogenous
2. ) Endogenous
3. ) Reverse cholesterol transport
38
Deals with dietary lipids and originates in the intestine
Exogenous pathway
39
Deals largely with de novo synthesized lipids and originates in the liver
Endogenou spathway
40
Deals largely with cholesterol in the peripheral tissues
Reverse cholesterol transport pathway
41
Dietary lipids are taken up by intestinal epithelial cells and are released into the lymphatic system inside of chylomicrons in the
Exogenous pathway
42
Then, on the walls of blood capillaries, triglycerides are hydrolyzed to FFAs and glycerol by
LPL
43
A similar reaction is catalyzed in the walls of the liver by
HL
44
Through the removal of triglycerides by LPL in the exogenous pathway, chylomicrons become remnants and they are taken up by the
Liver
45
As for the endogenous pathway, the liver exports cholesterol and cholesterol esters in
VLDL
46
Then, lipases remove triglycerides, thereby converting VLDL to
IDL and LDL
47
Contains much more cholesterol than it does triglycerides
LDL
48
Then, in the endogenous pathway, liver and peripheral cells endocytose the cholesterol-rich
LDL
49
In the reverse cholesterol transport pathway, extrahepatic tissues export cholesterol by adding it to circulating
HDL
50
This cholesterol is then delivered mainly to the
Liver
51
Located at the apical membrane of enterocytes and facilitates the uptake of cholesterol across the brush border membrane
NPC1L1 protein
52
Promotes the active transfer of cholesterol and plant sterols back into the intestinal lumen for secretion
ABCG5/G8 transporter
53
This absorbed cholesterol is esterified by
-is then incorporated into nascent chylomicron particles
Acyl CoA cholesterol acyltransferase 2 (ACAT2)
54
Synthesized around the ApoB-48 in the ER
Chylomicrons
55
Dietary fatty acids are used for triglyceride synthesis in the
Smooth ER
56
Transfers triglycerides and cholesterol esters to ApoB-48
Microsomal Triglyceride Transfer Protein (MTP)
57
The nascent chylomicrons leave the ER and are secreted through the Golgi complex to the basolateral side of the
Enterocyte
58
In the blood, chylomicrons gain ApoC-II and III and ApoE from
HDL
59
Necessary for the uptake of chylomicron remnants by the liver
ApoC-III and ApoE
60
Chylomicron remnants (but not chylomicrons) are small enough to enter the
Space of Disse in the liver
61
In the space of Disse in the liver, we see triglyceride removal by
HL
62
ApoE on chylomicron remnants binds to the
-Results in remnants entering hepatocytes via endocytosis
LDL receptor-related protein 1 (LRP1)
63
The chylomicron remnants are then degraded by
Lysozomes
64
Absorption of the fat soluble vitamins A, D, E, and K occurs in the small intestine, and these vitamins are transported ot the liver by
Chylomicrons
65
The halflife for a given chylomicron is
Minutes
66
Fasting blood samples are used to determine lipids in order to prevent contamination by
Chylomicrons
67
Ancompasses the triglycerides inside all lipoprotein particles, i.e. chylomicrons, chylomicron remnants, VLDL, IDL, LDL, and HDL
Total triglycerides
68
The nascent chylomicron enters the circulation carrying ApoB-48 and a large cargo of
Triacylglycerol
69
It then receives ApoE and C-II from
HDL
70
The chylomicrons travel around the circulatory system until they associate with
LPL
71
As triacylglycerol is lost, the chylomicron shrinks and forms a
Chylomicron Remnant (CMR)
72
The released fatty acids can be reassembled into triacylglycerol for storage as fat or oxidized to produce
ATP
73
The remnant is taken up by the liver through receptor mediated endocytosis because the liver recognizes
ApoB-48 and ApoE
74
Dietary cholesterol delivered to the liver in CMR can be repackaged in VLDLs and sent out to tissues or converted to
Bile salts
75
Inhibits cholesterol synthesis by the liver
Dietary cholesterol
76
The counterparts to the chylomicron and exogenous pathway is
VLDL and the endogenous pathway
77
VLDLs are created in the liver, containing "endogenous"
TAGs and CEs
78
The liver synthesizes a small amount of fatty acids from excess dietary carbohydrate and esterifies these fatty acids with glycerol to form
Triglycerides
79
The liver packages triglycerides into
-released into blood
VLDLs
80
Nascent VLDL enters the circulation containing
APoB-100 and some ApoE and C-II
81
As ith chylomicrons, additional ApoE and ApoC-II are donated to VLDL from
HDL
82
The presence of ApoC-II stimulates LPL to degrade the
TAGs present in VLDL
83
This results in the delivery of liver-originating FFAs to adipose and other
Peripheral organs
84
The resulting action of LPL on VLDL is its conversion to the
VLDL remnant (AKA IDL [intermediate density lipoprotein])
85
What is the halflife of VLDL?
Hours
86
Approximately half of the VLDL remnants are cleared from the circulation by the liver via
ApoE and its receptor
87
The remaining half of IDL is remodeled to
-remains in circulation
LDL
88
The conversion of IDL to LDL involves the removal of both TAGs and phospholipids and requires the action of
HL
89
As a consequence of the cumulative action of LPL and HL on these particles, the LDL particle is significantly enriched in
Cholesterol Esters (CEs)
90
The half-life of LDL particles is long, on the order of
Days
91
The majority of lipids observed in a fasting blood sample is
LDL, VLDL, and IDL
92
The majority of blood-borne cholesterol is from
LDL
93
Throughout the body, LDL's ApoB-100 acts as a ligand for
LDL receptors (LDLR)
94
Approximately 2/3 of the circulating LDL is taken up by the liver via
ApoB-100 binding to LDL receptors
95
The remaining 1/3 is taken up via ApoB-100 and the LDL receptor in
Peripheral tissues
96
NOT the only mechanism for the clearance of LDL particles form blood
LDLR
97
After endocytosis of LDL, triglycerides and cholesterol esters are hydrolyzed in lissomes by
Lysosomal acid lipase
98
What percentage of all of the LDL is taken up by the liver?
Approximately 70%
99
Acts on LDL receptors to prevent their recycling to the plasma membrane surface and promote their degradation in lysosomes
PCSK9
100
An integral part of the cholesterol-dependent regulation of the number of LDLRs
PCSK9
