Question

Which of the plasma proteins contributes most to osmotic pressure? a. albumin c. erythrocytes b. globulins d. fibrinogen

Short answer

a. albumin

Step-by-step solution

Define osmotic pressure

Osmotic pressure is the pressure required to prevent the movement of solvent molecules across a semipermeable membrane due to differences in solute concentrations. In the context of blood plasma, osmotic pressure plays a crucial role in maintaining the balance between fluid inside and outside of blood vessels.

Introduce plasma proteins

Plasma proteins are essential components of blood plasma, which serve a variety of functions such as transport, clotting, and maintaining osmotic pressure. The main types of plasma proteins include albumin, globulins, and fibrinogen. Erythrocytes, although present in blood, are not plasma proteins, but rather red blood cells.

Discuss albumin's role in osmotic pressure

Albumin is the most abundant plasma protein, accounting for about 60% of the total plasma protein concentration. Its primary function is to maintain osmotic pressure inside the blood vessels. Albumin helps in retaining water inside the blood vessels by creating an osmotic pressure to counteract hydrostatic pressure, preventing excess fluid from leaking into surrounding tissues.

Discuss globulins' role in osmotic pressure

Globulins are another class of plasma proteins that include three different subgroups: alpha, beta, and gamma globulins. These proteins carry out various functions such as transporting nutrients, immune response, and blood clotting. Although globulins contribute to osmotic pressure as well, their contribution is less significant than that of albumin.

Discuss fibrinogen's role in osmotic pressure

Fibrinogen is the least abundant plasma protein and plays a crucial role in blood clotting. It gets converted into fibrin during clotting, holding platelets together to form a clot. While fibrinogen does contribute to osmotic pressure, its contribution is minimal compared to albumin.

Determine the major contributing component to osmotic pressure

Based on the discussion above, it is clear that albumin is the plasma protein that contributes most to osmotic pressure, due to its high concentration and primary function in maintaining osmotic pressure within the blood vessels. Therefore, the correct answer is: a. albumin