Biology · Body Fluids and Circulation · NEET
No, but they are very close. Both are the liquid part of blood. The key difference: plasma still has the clotting factors (like fibrinogen), while serum is plasma AFTER the clotting factors are used up or removed. So serum = plasma minus clotting factors.
No. Fibrinogen is a clotting factor. When blood clots, fibrinogen is converted into fibrin (the clot). Since serum is what is left after clotting, the fibrinogen is gone. Plasma still has fibrinogen, serum does not.
Let a blood sample stand and clot on its own (no anticoagulant added). The clot traps the cells and fibrin. The clear liquid that separates out on top is serum. To get plasma instead, you add an anticoagulant so blood does NOT clot, then spin it; the liquid on top is plasma (still with fibrinogen).
Yes. Serum keeps most plasma proteins like albumins and globulins. Antibodies are globulins, so serum still has them. Only the clotting factors (fibrinogen and others) are missing. This is why serum is used in many blood tests for antibodies.
Plasma still contains the clotting factors needed to form a clot. Serum has already lost those factors during clotting, so it cannot clot again. This is the single most tested point in NEET.
Serum differs from blood in
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Serum is plasma without the clotting factors (like fibrinogen). Plasma has clotting factors, serum does not.
Serum is often used because it still has antibodies (globulins) but no clotting factors to interfere. Both, however, can carry antibodies.
Yes. Both plasma and serum are straw-coloured (pale yellow) liquids. Removing clotting factors does not change the colour much.
Plasma. An anticoagulant stops clotting, so fibrinogen stays. You get plasma. If you let blood clot naturally without anticoagulant, you get serum.
Yes. It appears in Body Fluids and Circulation and has been directly asked in NEET (2016), so it is high-yield for one easy mark.
