Which component does plasma contain that serum does not?

Plasma is the liquid component of blood that remains after the blood has been treated with an anticoagulant to prevent clotting. It contains clotting factors, which are essential proteins that help regulate the clotting process. These factors are present in plasma because they are part of the blood's natural hemostatic mechanism that prevents excessive bleeding.

Serum, on the other hand, is derived from blood that has been allowed to clot. It is the liquid portion that remains after the coagulation process has taken place. Since the clotting factors are utilized during this process to form a clot, they are absent in serum. Therefore, the primary distinction between plasma and serum is the presence of these clotting factors in plasma.

This understanding is crucial for various applications in blood banking and clinical practice, as it informs decisions related to transfusions and the use of blood components for therapeutic purposes.