Which of the following is NOT a function of plasma?

• A. Coagulation
• B. Immunity
• C. Oxygen transport
• D. pH balance

Answer: (C)

Oxygen transport is not a function of plasma because the primary carrier of oxygen in the blood is hemoglobin inside red blood cells. Hemoglobin binds oxygen in the lungs and releases it to tissues as needed, providing most of the blood’s oxygen-carrying capacity. Plasma can hold only a small amount of dissolved oxygen, which is not enough to meet the body's needs, so oxygen transport relies on red blood cells rather than plasma.

Coagulation is a plasma function because many clotting factors circulate in plasma and are essential for forming a fibrin clot. Immunity relies on plasma proteins like antibodies and complement components that circulate in the plasma to recognize and help clear pathogens. pH balance is also supported by plasma, especially through the bicarbonate buffering system and various plasma proteins that act as buffers, helping maintain acid-base homeostasis.