Which component is not typically found in serum?

Serum is the clear fluid that remains after blood has clotted and the cells and clotting factors have been removed. Clotting factors, such as fibrinogen, are proteins involved in the coagulation process to help blood clot. Since serum is derived from blood that has been allowed to clot, it does not contain these clotting factors.

In contrast, electrolytes (such as sodium, potassium, calcium), proteins (including albumin and globulins), and water are all components typically found in serum. Electrolytes play crucial roles in maintaining fluid balance and other physiological functions, proteins serve various roles including transport and immune response, and water makes up a significant portion of the serum's composition. Therefore, the absence of clotting factors in serum is what distinguishes it from other components of whole blood.