_______________ is the most abundant protein found in plasma and maintains blood osmolarity.

• A. Fibrinogen
• B. Albumin
• C. Globulin
• D. Hemoglobin

Answer: (B)

Albumin is the most abundant protein in blood plasma and is the primary driver of colloid (oncotic) pressure. This pressure pulls fluid back into the capillaries from the surrounding tissue, helping to keep blood volume stable and preventing excess fluid leakage into tissues. Albumin is produced by the liver and accounts for about 60% of plasma proteins, which is why it has the biggest impact on maintaining fluid balance in the vascular system. The other proteins have important roles—fibrinogen is a clotting factor present in smaller amounts; globulins include antibodies and transport proteins but are less abundant than albumin; and hemoglobin is inside red blood cells, not in plasma, so it doesn’t contribute to plasma osmotic pressure.