Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st year (First Year) Biochemistry ppt lectures Topic 6 L7 Lipoprotein Notes. - biochemistry notes pdf, biochemistry mbbs 1st year notes pdf, biochemistry mbbs notes pdf, biochemistry lecture notes, paramedical biochemistry notes, medical biochemistry pdf, biochemistry lecture notes 2022 ppt, biochemistry pdf.
Lipoproteins
Lipoproteins
? Lipoproteins are types of
Compound Lipids /Conjugated
Proteins.
? Lipoproteins are macromolecules
formed by aggregation of :
? Lipids (Neutral and Amphipathic )
? Proteins( Apoprotein) in the
human body.
? Lipoproteins acquire polarity
(Hydrophilic Property)
? Lipoprotein serve as vehicles
for transportation of Neutral
and Amphipathic Lipids
through aqueous media blood
and lymph.
?Lipoproteins are
biosynthesized within the
cells of tissues.
?By aggregation of various
forms of Lipids and
Apoproteins.
Structure Of Lipoproteins
Structure of Lipoproteins
? The non polar /hydrophobic Lipids TAG and
Cholesterol Ester are gathered central y to
form the core of LipoProtein particle.
? At the periphery of Lipoprotein are
Apoprotein and Amphipathic Lipids viz
Phospholipids and Cholesterol.
? The Apoprotein and polar groups of
Amphipathic Lipids impart
hydrophilic property to Lipoprotein
molecules
? This helps in transportation of
Lipids
? From site of origin to site of
utilization through blood.
Cholesterol Transported as Lipoprotein
Complex (LDL)
Functions Of Lipoproteins
? Lipoproteins serve as a vehicle in
transportation of non polar Lipids
? From the site of its biosynthesis to
the site of utilization through
aqueous media of blood or lymph.
Types Of Lipoproteins
? Depending upon the composition and other
properties following are the types of
Lipoproteins:
?Chylomicrons (CM)
?Very Low Density Lipoprotein (VLDL)
?Low Density Lipoproteins (LDL)
?High Density Lipoproteins (HDL)
?Free Fatty acid -Albumin
Lipoproteins
Lipoproteins
Types of Lipoprotein
(al contain characteristic amounts TAG, cholesterol, cholesterol esters,
phospholipids and Apoproteins ? NMR Spectroscopy)
Diameter
Major
Class
(nm)
Source and Function
Apoliproteins
Chylomicrons
500
Intestine. Transport of
A, B48,
(CM)
Largest
dietary TAG
C(I,II,III) E
ty
Very low density
43
Liver. Transport of
B100,
si
lipoproteins
endogenously
C(I,II,III) , E
(VLDL)
synthesised TAG
n
g
d
en
Low density
22
Formed in circulation by
B100
lipoproteins
partial breakdown of IDL.
(LDL)
Delivers cholesterol to
I
n
creasi
peripheral tissues
High density
8
Liver. Removes "used"
A, C(I,II,III),
lipoproteins
Smal est
cholesterol from tissues
D, E
(HDL)
and takes it to liver.
Donates apolipoproteins to
CM and VLDL
Features Chylomicrons VLDL
LDL
HDL
Site of
Small
Hepatocytes
Blood
Nascent HDL
Synthesis Intestine
Liver -80%
Circulation Liver
Intestine -20% From VLDL
Lipids %
99%
92%
80%
50%
Protein % 1%
8%
20%
50%
Rich Lipid TAG
TAG
Cholester Phospholipids
Form
Exogenous
Endogenous ol
Associate Apo B48, Apo Apo B100,Apo Apo B100, Apo A I,Apo A II
d
CI ,Apo E
CI,Apo CI ,Apo Apo CI,
Apo C I, Apo C II
Apoprote
E
Apo CI
Apo D & Apo E
in
and Apo E
Transport Dietary Lipids Liver
Liver
Extrahepatic
From
Intestine
Tissues
Transport Liver
Extrahepatic Extrahepa Liver
To
Tissues
tic Tissues
HDL Has Scavenging Role
OR
Reverse Transport of
Cholesterol
HDL Is Associated
With Enzyme LCAT
Responsible For
Cholesterol
Esterification And Its
Excretion
? HDL has scavenging role with
protective mechanism.
? HDL Transports Cholesterol from
Extrahepatic tissues back to Liver for
its excretion.
? HDL reduces risk of
Atherosclerosis.
? HDL clears the body Lipids and
do not al ow accumulation of
Lipids in blood.
?Thus when the levels of
HDL are within normal
range
?Cholesterol associated
with HDL is termed as
Good Cholesterol
? Based on Electrophoretic pattern
the Lipoproteins are termed as:
?LDL: Beta Lipoproteins
?VLDL: Pre Beta Lipoproteins
?HDL: Alpha Lipoproteins
Classification of plasma Lipoproteins
according to their electrophoretic
mobility
(CM)
a-lipoprotein (HDL)
Pre-b-Lipoprotein (VLDL)
b-lipoprotein (LDL)
CM
Lipoprotein
Density Diameter
Protein % Phospholi Triacyl-
class
(g/mL)
(nm)
of dry wt
pids %
glycerols %
of dry wt
HDL
1.063-
5 ? 15
50
29
8
1.21
LDL
1.019 ? 18 ? 28
25
21
4
1.063
IDL
1.006-
25 - 50
18
22
31
1.019
VLDL
0.95 ?
30 - 80
10
18
50
1.006
Chylomicrons
< 0.95
100 - 500
1 - 2
7
84
99
Physical properties and lipid compositions of Lipoproteins
CM
VLDL
LDL
HDL
Density (g/ml)
< 0.94 0.94-1.006 1.006-1.063 1.063-1.210
6000-
Diameter (?)
2000
600
250
70-120
Total lipid (wt%) * 99
91
80
50
Triacylglycerol
85
55
10
6
Cholesterol esters 3
18
50
40
Cholesterol
2
7
11
7
Phospholipid
8
20
29
46
Apoprotein % 1 9 20 50
Fatty acid compositions (wt% of the total) in the main lipids of human Lipoprotein
Triacylglycerols Cholesterol
Esters
Phospholipids
Fatty acid VLDL LDL HDL VLDL
LDL HDL VLDL LDL HDL
16:0 27
23 23
12
11 11
34
36
32
18:0 3
3
4
1
1
1
15
14
14
18:1 45
47 44
26
22 22
12
12
12
18:2 16
16 16
52
60 55
20
19
21
20:4
(n-6) 2
5
8
6
7
6
14
13
16
The main properties of the Apoproteins.*
Apoprotein
Molecular weight
Lipoprotein
Function
Lecithin:cholesterol
Apo A1
28,100
HDL
acyltransferase (LCAT)
activation. Main structural
protein.
Apo A2
17,400
HDL
Enhances hepatic lipase
activity
Apo A4
46,000
CHYLOMICRON(CM)
Apo AV(5)
39,000
HDL
Enhances triacylglycerol
uptake
Apo B48
241,000
CHYLOMICRON
Derived from Apo B100 ?
lacks the LDL receptor
Apo B100
512,000
LDL, VLDL
Binds to LDL receptor
Apo C1
7,600
VLDL, CM
Activates LCAT
Apo C2
8,900
VLDL, CM
Activates lipoprotein lipase
Apo C3
8,700
VLDL, CM
Inhibits lipoprotein lipase
Apo D
33,000
HDL
Associated with LCAT,
progesterone binding
Apo E
34,000
HDL
At least 3 forms. Binds to
LDL receptor
Linked by disulfide bond to
Apo(a)
300,000-800,000
LDL, Lp(a)
apo B100 and similar to
plasminogen
Apo H, J, L
Poorly defined functions
Apo M
HDL
Transports sphingosine-1-
phosphate
* Roman numerals are sometimes used to designate apoproteins (e.g. Apo AI, AI , AI I, etc)
Disorders Of Lipoproteins
? Defect in Lipoprotein
metabolism leads to
Lipoprotein disorders:
? Hyperlipoproteinemias
? Hypolipoproteinemias
Lipoproteins Atherogenic Particles
MEASUREMENTS:
Apolipoprotein B
Non-HDL-C
VLDL
VLDL
IDL
R
LDL
Small,
dense
TG-rich lipoproteins
LDL
? Defect in the receptors of
Lipoproteins on specific
tissues
? Leads to retention of
specific Lipoproteins in the
blood circulation.
? Abnormal high levels of LDL in
blood is due to LDL receptor
defect on extrahepatocytes
bad to body.
? The Cholesterol associated to
high LDL levels is said to be
bad Cholesterol.
? This increases the risk of
Atherosclerosis ,Ischemia, MI
and Stroke.
? Recently evidenced high levels
of blood HDL are also bad to
body.
? This increases the risk of
Atherosclerosis ,Ischemia, MI
and Stroke.
Proteolipids/ Lipophilin
Proteolipids/ Lipophilin
? Proteolipids are compound lipids
which have more content of
Proteins than Lipids.
? Proteolipid is a transmembrane
domain protein bound with Lipids.
Occurrence Of Proteolipids
? Proteolipids are structural
Lipids
? Present on the extracel ular
side of the membrane.
? Proteolipids are also present in
Myelin Sheath.
This post was last modified on 05 April 2022