COMPOSITION OF PLASMA

A. Water: Plasma contains 90% water by volume.
B. Solutes: Plasma contains 10% solutes by volume. These solutes include plasma proteins and other organic compounds as well as inorganic salts.
1. Plasma proteins. Plasma contains a rich variety of soluble proteins, 7% by volume. Important examples include: a. Albumin. This is the most abundant plasma protein (3.5-5 g/dL of blood) and is mainly responsible for maintaining the osmotic pressure of blood. B. Globulins. Alpha, beta, and gamma globulins are globular proteins dissolved in the plasma. The gamma globulins include the antibodies, or immunoglobulins, synthesized by plasma cells. c. Fibrinogen. This protein is converted by blood-borne enzymes into fibrin during clot formation. Fibrinogen is synthesized and secreted by the liver. 2. Other organic compounds. Other organic molecules in plasma, include nutrients such as amino acids and glucose, vitamins, and a variety of regulatory peptides, steroid hormones, and lipids. 3. Inorganic salts. Inorganic salts in plasma, 0.9% by volume, include blood electrolytes such as sodium, potassium, and calcium salts.