San Diego State University Plasma Proteins Paper Synthesis of plasma proteins synthesized by : [the liver only] (albumin, α1-globulin, α2-globulin, β-gl
San Diego State University Plasma Proteins Paper Synthesis of plasma proteins
synthesized by :
[the liver only]
(albumin, α1-globulin, α2-globulin, β-globulin and fibrinogen are)
synthesized by :
[plasma cells]
*in the lymphoid tissues
(ƴ-globulins )
*ƴ-globulins constitute the antibodies used in the immune system.
Plasma proteins
Plasma contains a many proteins with different functions
It has major clasas .. they are
1.Albumin.
2.Globulin.
3.Fibrinogen.
Plasma
proteins
Plasma contains a variety of proteins with different functions.
The major classes of plasma proteins are:
1. Albumin.
2. Globulin.
3. Fibrinogen.
Plasma proteins are generally divided into five classes based on their behavior
during electrophoresis (electrophoresis is an analytical technique used to separate
proteins, DNA and RNA).
• The five major classes of plasma proteins are:
1. Albumin.
2. α1-globulin.
3. α2-globulin.
4. β-globulin.
5. ƴ-globulin.
Albumi
n
• Albumin is a globular protein consisting of single polypeptide.
• It is the most abundant protein found in plasma, accounting for approximately
(50 – 60 %) of plasma protein mass.
• Albumin is exclusively synthesized by the liver for this reason, serum albumin
levels are determined to assess liver function (synthesis decreased in liver
diseases).
• The normal plasma half-life of albumin is 15 – 20 days.
Functions of
albumins
1. Albumin’s primary function is the maintenance of colloidal osmotic
pressure. Thus, albumin plays a predominant role in maintaining
blood volume and body fluid distribution. Very low albumin
concentration develops edema.
2. Albumin binds and transports many metabolites which are poorly
soluble in water such as: fatty acids, bilirubin, inorganic ions (e.g.
Ca2+), hormones and drugs.
3. Nutritive function: Degradation of albumin provides essential
Clinical significance of
albumin
• Serum albumin measurements are used to assess the various clinical
conditions. Decreased serum albumin also known as hypoalbuminemia is
caused by two general mechanisms:
1. Defective synthesis by liver, mostly a late stage liver disease, as, fibrosis and
cancer.
2. Failure of nephrons to keep albumin, leading to leakage into urine, in micro
amounts (micro albuminuria), or larger amounts (albuminuria).
In both cases, plasma albumin deficiency, leads to edema.
Hypoalbuminemi
a
Hypoalbuminemia is defined as decreased level of plasma albumin.
Hypoalbuminemia is seen in:
1. Malnutrition.
2. Nephrotic syndrome.
3. Liver disease.
Malnutrition
In malnutrition, due to insufficient intake of proteins, the availability of
amino acid is reduced and so albumin synthesis is affected.
2. Nephrotic syndrome
In nephrotic syndrome, large amounts of protein are lost in urine
(proteinuria or albuminuria).
3. Liver disease
In liver diseases and especially cirrhosis, albumin synthesis is
decreased and so blood level is lowered.
Globulins are bigger in size than albumin. Globulins are broadly
divided into four classes. These are:
1. α1-globulin.
2. α2-globulin.
3. β-globulin.
4. ƴ-globulin.
