type and functions of plasma proteins

1. PLASMA PROTEINS
Dr. Sanjeev Shrivastava

2. Plasma Proteins
• The normal serum protein level is 6.3-8.3 g/dL.
• • The type of proteins in serum include:
• a. Albumin- 4.8 g/dL
• b. Globulins- 2.3 g/dL
α− globulin: α1 & α2−globulins
β− globulin: β1 & β2 globulins
γ− globulins
• c. Fibrinogen - 0.3 g/dL
• d. Prothombin -

3. Synthesis of plasma proteins
 IN EMBRYO-
- Plasma proteins are synthesized by mesenchymal
cells.
 IN ADULT-
-albumin and fibrinogen – Reticuloendothelial cells of
liver.
-alpha and beta globulins- liver , spleen, bone marrow
-Gamma globulins – B Lymphocyte

4. MEASUREMENT OF PROTEIN
FRACTIONS
• The protein fraction in plasma can be
separated and estimated using the following
methods:
– Electrophoresis
_ Precipitation
– Immuno-electrophoretic method
– Salting out method
– Ultracentrifugation

5. Plasma proteins
 simple or conjugated (glycoproteins, lipoproteins)
 separation:
 a) salting-out methods  albumin, globulins, fibrinogen
 b) electrophoresis  albumin, globulin 1, 2, ,  fractions:
-
+


2
1
albumin

6. ALBUMIN
• A low molecular weight protein (M.Wt= 65,000).
• Functions include:
– Transport
– Osmotic pressure regulation
• Synthesized in the liver.
• Deficiency: in liver disease and kidney disease.

7. HYPOALBUMINAEMIA
• Normal albumin level = 3.2-5.2 g/dL.
• Hypoalbuminaemia: the level of albumin <3.2
g/dL.
• Frequently encountered.
• Consequence:
– Oedema
– Hypocalcaemia
– Alteration in the levels of protein-bound
substance due to loss of carrier protein.

8. GLOBULINS
• Heterogenous group
• Can be separated into different fractions on the
basis of their electrophoretic mobility and
sedimentation coefficient:
- α1-Globulin - α1- Fetoprotein
α1- Antitrypsin
- α2- Globulin - α2- Fetoprotein
Haptoglobin
- β- Globulin - Transferrin
Ceruloplasmin
- γ- Globulin - Antibodies
(immunoglobulins)

9. FIBRINOGEN
• A globulin of very high mol. wt.
• Can be precipitated easily.
• Can be converted to fibrin which causes the
blood clot formation.
• Synthesized exclusively in the liver.

10. A/G Ratio
 Normal albumin: globulin ratio- 1.7:1 (2:1)
 It is reversed when albumin synthesis
decreased as occurs in liver diseases,
and when globulin increased as occurs in
hyperproteinaemia.

11. SERUM PROTEIN DEFECTS
• Normal serum protein levels:
Total serum protein level: 6.3-8.3 g/dL.
• Hyperproteinaemia:
Total serum protein level: > 9.0 g/dL.
• Hypoproteinaemia:
Total serum protein level: < 6.3 g/dL.

12. Functions of Plasma proteins
• Osmotic regulation:
- Plasma proteins are colloidal and non-diffusable
and exert a colloidal osmotic pressure which helps
to maintain a normal blood volume and a normal
water content in the interstitial fluid and the
tissues.
- Albumin content is most important in regulation of
colloidal osmotic or oncotic pressure.
- Decrease in albumin level results in loss of water
from blood and its entry into interstitial fluids
causing edema.

14. Functions of Plasma proteins
 Contribution to blood viscosity-
- Fibrinogen and albumin are significant contributor to
blood viscosity.
- It is 4-5 times that of water.
- It play important role to maintenance of the blood
pressure.
 Role as reserve proteins-
Plasma proteins serve as reserve proteins and utilized
by tissues during condition like- starvation, inadequate
protein intake, excessive catabolism.

15. Functions of Plasma proteins
• Protective function:
- Immunoglobulins combine with foreign antigens
and remove them.
 Provide stability to blood- Globulin and fibrinogen
help in the suspension stability to blood. RBCs
remain suspended uniformly in blood during
circulation.

16. Functions of Plasma proteins
• Transport: e.g.
-Transferrin transports iron.
- Ceruloplasmin transports copper.
- Albumin transports fatty acids, bilirubin
calcium, many drugs etc.
-Transcortin transports cortisol and corticosterone
- Retinol binding protein transports retinol.
- Lipoproteins transport lipids.
- Haptoglobin transports free haemoglobin.
-Thyroxin binding globulin transports thyroxin.

17. Functions of Plasma proteins
• Blood clotting:
- Many factors are involved in clotting mechanism
and prevent loss of excessive amount of blood.
e.g. clotting factors IX,VIII, thrombin, fibrinogen
etc.
- An excess of deficiency leads to a disease. e.g
hemophilia, thrombus formation.
• Anticoagulant activity (thrombolysis):
- Plasmin breaks down thrombin and dissolves the
clot

18. Functions of Plasma proteins
• Catalytic function (enzymes):
- e.g.- lipases for removal of lipids from the
blood.
• Buffering capacity:
- Proteins in plasma help to maintain acid-base
balance.

19. Plasmapheresis/Whipple’s
experiment
 To demonstrates the importance of plasma protein
 Dogs – blood is removed completely washed in saline
and re-infused into the body with a solution.
 Due to lack of proteins the animal undergoes the state
of shock. If animal fed with diet containing proteins the
normal level of PP is restored.These synthasized by
liver of dog.
 After removal of liver , the shock persist and animal
lead to death.
 Importance- PP are essential for survival.
- pp mainly synthesized by liver.