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Plasma resembles whey in appearance (transparent with a faint straw colour). It is mainly composed of water, proteins, and mineral salts. It serves as transport medium for glucose, lipids, hormones, products of metabolism, carbon dioxideCarbon dioxide is an atmospheric gas composed of one carbon and two oxygen atoms. One of the best known of chemical compounds, it is frequently called by its formula: :CO (pronunciation: "see oh two") Carbon dioxide results from the combustion of organic and oxygenOxygen is the chemical element in the periodic table that has the symbol O and atomic number 8. The element is very common, found not only on Earth but throughout the universe. Molecular oxygen (O, often called free oxygen on Earth is thermodynamically un. (Oxygen transport capacity of plasma is lower compared to that of the hemoglobinHaemoglobin ( BE) or hemoglobin ( AE), is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. The molecule consists of globin, the apoprotein, and four haem groups, an organic molecule with an ir in the red blood cellRed blood cells are the most common type of blood cell and are the vertebrate body's principal means of delivering oxygen to body tissues via the blood. Red blood cells are also known as erythrocytes from Greek erythros for "red" and kytos for "hollow", ns; it may increase under hyperbaricHyperbaric oxygen therapy (HBOT) is the medical use of oxygen at a higher than atmospheric pressure. Several therapeutic principles are made use of in HBOT: The increased overall pressure is of therapeutic value when HBOT is used in the treatment of decom conditions.) It is the storage and transport medium of clotting factors and its protein content is necessary to maintain the oncotic pressureIn blood plasma, the dissolved compounds have an osmotic pressure. A small portion of the total osmotic pressure is due to the presence of large protein molecules; this is known as the colloidal osmotic pressure or oncotic pressure . Because large plasma of the blood.

Laboratory use of plasma and serum

For purposes of laboratory tests, plasma is obtained from whole blood. To prevent clottingCoagulation is the thickening or congealing of any liquid into solid clots. This article is about a specific medical usage of the term with reference to human blood's mechanisms for forming scabs over wounds. The coagulation of human blood is a fairly com, an anticoagulantAn anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some chemical compounds are used in medical eq such as citrate or heparin is added to the blood specimen immediately after it is obtained. (Usually the anticoagulant is already in the vacutainer when the patient is bled.) The specimen is then centrifuged to separate plasma from blood cells. Plasma can be frozen below -80 °C nearly indefinitely for subsequent analysis.

For many biochemical laboratory tests, plasma and blood serum can be used interchangeably. Serum resembles plasma in composition but lacks the coagulation factors. It is obtained by letting a blood specimen clot prior to centrifugation. For this purpose, a serum-separating tube (SST) can be used which contains an inert catalyst (such as glass beads or powder) to facilitate clotting as well as a portion of gel with a density designed to sit between the liquid and cellular layers in the tube after centrifugation, making separation more convenient.

Tests of coagulation (such as the INR and APTT) require all clotting factors to be preserved. Serum, therefore, is inappropriate for these tests. A citrated vacutainer is usually used, as the anticoagulant effects of citrate is dependent upon concentration and can be reversed for testing.

Serum is preferred for many tests as the anticoagulants in plasma can sometimes interfere with the results. Different anticoagulants interfere with different tests; using serum means the same sample can be used for many tests. In protein electrophoresis, using plasma causes an additional band to be seen, which might be mistaken for a paraprotein.