What is Plasma?

• A. White blood cells
• B. Platelets
• C. Erythrocytes
• D. Plasma

Answer: (D)

Plasma is the liquid part of blood. It’s mostly water and contains dissolved substances such as electrolytes, nutrients, hormones, waste products, and a range of plasma proteins, including clotting factors. It serves as the medium that transports blood cells and platelets around the body and helps maintain blood volume and pressure. In the lab, plasma is obtained by centrifuging blood that’s treated with an anticoagulant, so the cells settle, and the liquid portion stays above. If you let the blood clot and then remove the liquid, you get serum, which lacks clotting factors like fibrinogen. The other options describe the cellular components of blood—white blood cells, platelets, and red blood cells—rather than the liquid carrier that supports and distributes them. So the correct choice is the liquid component of blood that carries everything else.