Download MBBS Biochemistry PPT 6 L7 Lipoprotein Lecture Notes

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