This document discusses plasma proteins and their functions. It outlines that plasma proteins include albumin, globulins, acute phase proteins, and immunoglobulins. Albumin is the major plasma protein and serves important osmotic, transport, nutritive, and buffering functions. Globulins contain proteins like alpha-1 antitrypsin, alpha-2 macroglobulin, haptoglobin, ceruloplasmin, and transferrin. Acute phase proteins increase during infection or inflammation and include C-reactive protein.

1. PLASMA PROTEINS
-Yubraj Bhatta
M.SC.MLT Clinical Biochemistry
bhattayuvraj12@gmail.com

2. INTRODUCTION
 The plasma is the liquid medium of blood (55-60%), in
which the cell components— namely erythrocytes,
leukocytes, platelets—are suspended.
 If blood containing anticoagulants (e.g. heparin,
potassium oxalate) is centrifuged, the plasma separates
out as a supernatant while the cells remain at the bottom.
 The proteins present in plasma is known as plasma
protein.

3. TYPES
 There are several types of plasma proteins
i) Albumin
ii) Globulins
a) Alpha 1 antitrypsin
b) Alpha 2 macroglobulin
c) Haptoglobulin
d) Ceruloplasmin
e) Transferrin
f) Acute phase proteins
g) C- reactive proteins
h) Immunoglobulins

4. ALBUMIN
 Albumin is the major constituent (60%) of plasma
proteins with a concentration of 3.5-5.0g/dl.
 Molecular weight= 69,000
 Consist of single polypeptide chain of 585 amino acids
with 17 disulfide bonds.
 Synthesis: liver. Conveniently used to assess liver
function.
 Liver produces about 12g albumin per day which
represent 25% of the total hepatic protein synthesis.
 Half life: 20 days.

5. FUNCTION:
 Osmotic function: Due to its high concentration and low
molecular weight, albumin contributes to 75-80% of total
plasma osmotic pressure (25mm Hg).
 Helps in maintaining blood volume and body fluid
distribution.
 Decrease in plasma osmotic pressure, leading to
enhanced fluid retention in tissue spaces, causing edema.

6. II) TRANSPORT FUNCTION
 Plasma albumin binds to several biochemically important
compounds and transports them in the circulation. These
include free fatty acids, bilirubin, steroid hormones,
calcium and copper.

7. III) NUTRITIVE FUNCTION
 Albumin serves as a source of amino acids for tissue
protein synthesis to a limited extent, particularly in
nutritional deprivation of amino acids.

8. IV) BUFFERING FUNCTION:
 Among the plasma proteins, albumin has the maximum
buffering capacity. However, the buffering action of
albumin in plasma is not significant compared to
bicarbonate buffer system.

9. CLINICAL SIGNIFICANCE OF ALBUMIN
 Albumin, binding to certain compounds in the plasma,
prevents them from crossing the blood-brain barrier e.g.
albumin-bilirubin complex, albumin-free fatty acid
complex.
 Hypoalbuminemia (lowered plasma albumin), observed
in malnutrition, nephrotic syndrome and cirrhosis of liver
is associated with edema.

10.  Albumin is excreted into urine (albuminuria) in nephrotic
syndrome and in certain inflammatory conditions of
urinary tract. Microalbuminuria (30-300 mg/day) is
clinically important for predicting the future risk of renal
diseases
 Albumin is therapeutically useful for the treatment of
burns and hemorrhage.

11. GLOBULINS
 Globulins constitute several proteins that are separated
into four distinct bands (α1, α2, β and gamma-globulins)
on
 Globulins, in general, are bigger in size than albumin.
electrophoresis
 Important globulins are discussed in the next slide..

12. Α1 - ANTITRYPSIN
 α1 – antitrypsin, more recently called as α -anti-
proteinase, is a glycoprotein with 394 amino acids and a
molecular weight of 54,000.
 Major constituent of alpha 1 globulin fraction of plasma
proteins with a normal concentration of about 200mg/dl.
 α1 -Antitrypsin is a serine protease inhibitor. It
combines with trypsin, elastase and other protease
enzymes and inhibits their activity.

13. CLINICAL SIGNIFICANCE OF ALPHA 1
ANTITRYPSIN
 Seen mostly in 2 disease namely, emphysema and alpha
1 Antitrypsin deficiency liver disease.
 Emphysema: abnormal distension of lungs by air. At
least 5% of emphysema cases are due to the deficiency
of alpha-1-AT. This is associated with lung infections
(e.g. pneumonia)
 AAT deficiency and liver disease : This is due to the
accumulation of a mutant AAT which aggregates to form
polymers. These polymers, in turn cause liver damage
(hepatitis) followed by accumulation of collagen
resulting in fibrosis (cirrhosis).

14. Α2, MACROGLOBULIN:
 α2 -Macroglobulin concentration in plasma is elevated in
nephrotic syndrome. This is due to the fact that majority
of the low molecular weight proteins are lost in urine
(proteinuria) in this disorder.

15. HAPTOGLOBIN (HP)
 Haptoglobin (Hp), a glycoprotein, is an acute phase
protein. Its plasma concentration is increased in several
inflammatory conditions.
 Functions of haptoglobin:
Haptoglobin binds with the free hemoglobin (known as
extra-corpuscular hemoglobin) that spills into the plasma
due to hemolysis. The haptoglobin-hemoglobin (Hp-Hb)
complex cannot pass through glomeruli of kidney while
free Hb (mol. wt. 65,000) can. Haptoglobin, therefore,
prevents the loss of free Hb into urine.

16. CLINICAL SIGNIFICANCE OF HAPTOGLOBIN
 Plasma concentration of Hp is decreased in hemolytic
anemia. This is explained as follows. The half life of Hp
is about 5 days while that of Hp-Hb complex is 90 min.
In hemolytic anemia, free Hb in plasma is elevated
leading to increased formation of Hp-Hb complex. This
complex in turn, is rapidly cleared from the plasma
resulting in decreased Hp levels

17. CERULOPLASMIN
 Ceruloplasmin is a blue colored, copper— containing
alpha 2-globulin with a molecular weight of 150,000. Its
plasma concentration is about 30 mg/dl.
 Ceruloplasmin binds with almost 90% of plasma copper
(6 atoms of Cu bind to a molecule). This binding is
rather tight and, as a result, copper from ceruloplasmin is
not readily released to the tissues. Albumin carrying only
10% of plasma copper is the major supplier of copper to
the tissues.
 it is associated with Wilson’s disease

18. TRANSFERRIN
 Transferrin (Tf) is a glycoprotein with a molecular
weight of 76,000. It is associated with beta-globulin
fraction.
 Transferrin is a transporter of iron in the circulation.

19. ACUTE PHASE PROTEINS
 ACUTE PHASE PROTEINS Acute phase response
refers to a non-specific response to the stimulus of
infection, injury, various inflammatory conditions
(affecting tissue/organs), cancer etc. This phase is
associated with a characteristic pattern of changes in
certain plasma proteins, collectively referred to as acute
phase proteins e.g. alpha 1- antitrypsin, ceruloplasmin,
complement proteins, C-reactive protein.

20. C (CARBOHYDRATE)-REACTIVE PROTEIN
(CRP)
 CRP is a major component of acute phase proteins. It is
produced in the liver and is present in the circulation in
minute concentration (< 1 mg/dl). C-reactive protein (C
strands for carbohydrate to which it binds on the capsule
of pneumococi) is involved in the promotion of immune
system through the activation of complement cascade.
 Increased levels of high sensitive CRP (hs-CRP) in the
circulation (reference range 100–300 Pg/dl) are useful
for predicting the risk of coronary heart disease.