Which components are absent in serum but present in plasma?

The key components that are absent in serum but present in plasma are clotting factors, fibrin, platelets, and clotted blood cells. Plasma is the liquid portion of blood collected with an anticoagulant, retaining all these components, while serum is obtained after the blood has clotted, resulting in the removal of clotting factors and fibrin, as well as the retention of blood cells within the clot.