The substance that is present in both serum and plasma is

The fluid poion of blood is plasma. If whole blood is allowed to clot and the clot is removed, the remaining fluid is called serum. The serum has essentially same composition of plasma, except that its fibrinogen and clotting factors 2,5 and 8 have been removed and it has a higher serotonin content because of the breakdown of platelets during clotting. Ref: Ganong's Review of medical physiology, 24th edition.Pg no. 564