Question

Serum differs from blood in lacking
A. Globulins
B. Albumins
C. Clotting factors
D. Antibodies

Answer 1

Serum is the fluid portion of blood obtained after the blood cells and materials responsible for clotting are removed.

Complete Answer:
Blood consists of cellular as well as non-cellular components, including many cells and molecules actively involved in immune response. Blood delivers nutrients and oxygen to the cells and transports metabolic waste products like CO$_2$ away from those same cells. Whole blood consists of suspended cells and plasma.

The suspended cells in human blood are erythrocytes, non-nucleated cells that function to carry oxygen from the lungs to the tissues. About 0.1% of the cells in blood are nucleated cells called leukocytes or white blood cells. Leukocytes include the phagocytes of the innate immune system and lymphocytes, the cells active in the adaptive response. Platelets are also called thrombocytes.

Plasma contains proteins and other solute. Albumin is the main protein in plasma. Globulins are globular proteins produced by the liver and function in blood clotting and liver function. They are of three types as alpha, beta and gamma. Gamma globulins are antibodies which are formed by the B cells against the foreign antigen. Outside the body, whole blood or plasma quickly forms an insoluble fibrin clot, remaining liquid only when an anticoagulant such as potassium citrate or heparin is added. When blood clots, the insoluble protein traps the cells in a large, insoluble mass.

Serum contains soluble components like antibodies, antigens, electrolytes, hormones and exogenous substances such as drugs and microorganisms and all proteins except that used in blood clotting. Blood serum is a watery fluid of the blood that separates when blood clots. Serum can be obtained from blood plasma from which the protein fibrinogen or clotting factors have been removed. Thus serum contains no cells or clotting proteins.

The correct choice is C, clotting factors. Thus serum differs from blood by clotting factor.

Note: Blood plasma-clotting factor=Serum. Blood when treated with anticoagulant then liquid portion left behind after centrifugation is referred to as serum.