Phlebotomist Exam Prep

Answer: B - The difference between serum and plasma is that serum contains proteins and does not contain clotting factors, while plasma is the portion of blood that contains serum and clotting factors. Plasma is the fluid that blood cells reside in and represents about 55% of total blood volume. Plasma contains the clotting factors essential for formation of blood clots. Serum is the fluid left after a clot has formed, it does not contain clotting factors, but it does contain proteins such as serum albumin and serum globulin.