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.