Table of Contents
What is Serum?
Serum is the fluid in blood which contains all the blood cells and proteins except fibrinogens and clotting factor. In other words, the fluid remaining after clotting of blood is serum. Plasma of the blood has the same composition as the serum, except it does contain the fibrinogen and clotting factors.
The serum contains all sorts of proteins such as antigens, antibodies, electrolytes, hormones and even exogenous substances. Let us study the protein content of serum in brief.
Protein Content of Serum
The human blood serum has approximately 7% protein content, out of which two-thirds is albumin and the remaining one-third is globulin. Electrophoresis of the blood serum yields a large albumin peak and three small glubin peaks. The three types of globulin found in serum are alpha (1.5g), beta (1.9g) and gamma (1.1g).
Each globulin is a mixture of many different proteins as can be seen by the technique of immunoelectrophoresis.
Serum Albumin
Serum albumin accounts for almost 55% of the total blood protein. It is less heterogeneous than globulins such that it can be easily isolated in a crystallised form. The serum albumin can combine easily with acidic dyes, fatty acids, bilirubin and the yellow bile pigment. It functions as a carrier for certain biological substances.
The serum albumin also functions as a protective colloid that stabilises other proteins. The albumin molecule has a sulfhydryl group (-SH), it oxidises to form bonds with another sulfhydryl group of albumin and thus the molecule exists as a dimer. The isoelectric point of serum albumin is 4.7.
Globulins
The alpha-globulin is a mixture of conjugated proteins such as α-lipoproteins (a mixture of proteins and lipids) and mucoproteins which are a combination of proteins and carbohydrates. There are two mucoproteins: one is called α1-acid glycoprotein or orosomucoid and the other is haptoglobin which combines with the globin component of haemoglobin.
The beta-globulin contains two-metal binding proteins: ceruloplasmin and transferrin in addition to the mucoproteins and lipoproteins found in alpha-globulins. These metal binding proteins can bind with copper and iron respectively and are major carriers of both the metals.
The gamma-globulins are the most diverse and heterogeneous proteins of the blood serum. Their molecular weight ranges from 150,000 to as high as 800,000 Da. The most prominent gamma-globulins are immunoglobulins such as IgM and IgG.
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Also Read:
- What Is The Difference between Plasma and Serum?
- Plasma in Blood – An Overview Of Plasma and its Features
- Components of Blood – RBCs, WBCs, Platelets and Plasma
- Interesting Facts About Blood their Components and Functions
- Blood Groups – ABO Blood Group and Rh Group System
