Blood contains 55% plasma which is straw-colored liquid.
Plasma contains water (91.5%), plasma proteins (7%), and other solutes (1.5%).
Some of the proteins that are present in the blood are found elsewhere in the body also.
Those proteins that are confined to the blood are called plasma proteins.
Most of the plasma proteins are synthesized by the hepatocytes(liver cells), which include- Albumins (54% of the plasma proteins), Globulins (38% of the plasma proteins), and fibrinogen (7% of the plasma proteins).
Importance of the Plasma Proteins-
Albumins- They are the smallest and most numerous of all proteins, they are responsible for balancing colloid osmotic pressure, and give a major contribution to the blood viscosity. They transport fatty acids, and calcium and help in maintaining blood pH.
Globulins- Large proteins, they produce special gamma proteins called antibodies or immunoglobulins, which attack viruses and bacteria. Alpha and beta globulins help in the transportation of iron, lipids, and fat-soluble vitamins.
Fibrinogen- Large protein that plays an important role in blood clotting.
Final Answer-
Plasma proteins play an important role in osmotic balancing, transportation, and clotting and also take part in the body’s defense system.