Plasma is the clear, straw-colored liquid portion of the blood that carries cells and substances through the body. It is obtained by centrifuging blood that has been mixed with an anticoagulant to prevent clotting. Plasma constitutes about 92% of blood volume and contains proteins, glucose, minerals, and other nutrients that are transported to tissues and organs. Serum is similar to plasma but is obtained by allowing blood to clot and centrifuging the coagulated blood, so it does not contain clotting factors like fibrinogen. Both plasma and serum are used in medical diagnostic tests and research.