Plasma Proteins Types And Functions

Plasma is the clear, pitched-colored liquid spot of blood that rests after red blood cells, white blood cells, platelets, and other cellular parts are removed. It is the largest portion of human blood, constituting approximately 55 percent, and contains water, salts, enzymes, antibodies and other proteins separately.

The proteins exist in the plasma of human blood are a blend of proteins, glycoproteins, lipoproteins and other conjugated proteins are collectively called “Plasma Proteins“. These may be break up by salt precipitation, immunological technique and electrophoresis processes.

Types of Plasma Proteins:

The three prominent components of plasma proteins are referred as Albumin, globulin, and Fibrinogen. On a finer resolution by electrophoresis, these constitutes are break up as follows:

types and functions of plasma proteins


This is the most lavish class of plasma proteins, with favorable electrophoretic mobility. It is generally soluble in water ad is precipitated by wholly saturated ammonium sulfate. Albumin is synthesized in liver and includes of a single polypeptide long-term chain of almost 610 amino acids having a molecular weight of enormous 69,000. It is wealthy in a number of necessary amino acids like, lysine, leucine, valine, phenylalanine, threonine, arginine and histidine respectively. The acidic amino acids such as aspartic acid and glutamic acid are also dilated in albumin. The existence of these remaining part makes the molecule violently charged with positive and negative charges. Besides having a nutritive role, albumin performs as a transport carrier for different biomolecules likewise, fatty acids, trace elements, drugs and so forth. However, the other crucial play of albumin is in the balancing of osmotic pressure and fluid distribution between human blood and tissues.


By simply apply electrophoresis, you can divide plasma globulins into α1, α2,β and ¥-globulins that are synthesized in the liver, while ¥-globulins formation takes place in the cells of the reticuloendothelial system. The average rate of serum globulin (total) concentration is about to 2.5 gm / 100 ml by using Howe method.


This composition incorporates various complex proteins having carbohydrates and lipids. These are orosomucoid, α1-glycoprotein and α-lipoproteins all are very much thick portions. The normal serum level of α1-globulin is about to touch 0.42 gm/100 ml.

Orosomucoid is wealthy in carbohydrates. It is water-soluble, heat stable and has a molecular weight of 44,000, that is very much high. It provides a medium in transporting hexosamine complexes to tissues.

Lipoproteins are soluble portions which compose non-covalently bound lipid. These proteins perform mainly as transport carrier to various types of lipids in the human body.


This fragment also includes complex proteins like α2-glycoproteins, plasminogen, prothrombin, haptoglobin, ceruloplasmin (transports Cu) and α2-macroglobulin respectively. The average serum value of this proportion is 0.67 gm/100ml.

Plasminogen and prothrombin are in the non-functioning precursors of plasmin and thrombin respectively. Each of these proteins plays a significant part in blood clotting.

Haptoglobins are also called glycoproteins having a molecular weight of 85,000 and considering the heaviest spot in human blood. These are synthesized in the liver and having the ability to bind with any free hemoglobin that may appear in plasma because of lysis of erythrocytes and thus fend off excretion of Hb and iron associated with it.

Ceruloplasmin is a glycoprotein take growth in liver and is a significant part of copper metabolism in the human body. Nearly 95% of plasma copper is bound to this protein.


This portion of plasma proteins compose these various β-lipoproteins which are very much rich in lipid proportion. It also constitutes transferrin (siderophilin) which carries non-heme iron in plasma. The average serum range of β-globulins is about to touch 0.91 gm/100ml.

Transferrin is actually an iron transport protein. In plasma, it may be saturated even up to 33% with iron that sounds creepy. It has a minute amount of carbohydrate.


These are also called as Immunoglobulins and possess antibody activity. On the basis of their electrophoretic mobility, they are classified as IgG, IgA, and IgM.


It is a fibrous protein, having a molecular weight of 340,000. It has 6 polypeptide long-term chains that are tied together by disulfide bandages. Fibrinogen carries an important part in blood clothing where it is transformed to fibrin by thrombin.

Furthermore to the above mentioned complex proteins, the plasma carries a lot of enzymes like, acid phosphatase and alkaline phosphatase which have good diagnostic values.

Functions of Plasma Proteins:

  • Protein Nutrition: Plasma proteins perform as the main source by providing a course, whenever the require arises.
  • Osmotic Pressure and water balance: Plasma proteins apply an osmotic pressure of about 25 mm of Hg and therefore play a significant part in balancing a proper water percentage in between the tissues and home-blood. Plasma albumin is mostly accountable for this function because of its low molecular weight and the quantitative amount over other proteins. However, during the situation  of protein loss from the human body as be found in kidney diseases, a huge percentage of water moves to the tissues as a result edema may cause.
  • Buffering action: Plasma proteins play an important role in maintaining the pH of the body, i.e. seven, by performing asampholytes process.
  • Transport of Lipids: One of the most crucial works of plasma proteins is to deliver lipids and lipid soluble substances in the whole human body. Fatty acids and bilirubin are carried mainly by albumin, while on the other side cholesterol and phospholipids are transferred by the lipoproteins exist in β-globulins also transport fat-soluble vitamins.
  • Transport of other complexes salts: If we considering to lipids, plasma proteins also helping in transporting various metals and other substances, i.e. thyroxine etc.
  • Blood Coagulation: Prothrombin that present in α2-globulin fraction and fibrinogen, take part in the blood clotting.

Hi, This is Hamza Khan from Peshawar, Pakistan. I am a 2nd prof MBBS Student at Bannu Medical College and a hobby Blogger. The Purpose of this site is to share my knowledge and Guide new Medical Students.

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