text: what is a serum?   serum (latin for "whey") may refer to:      * blood plasma with its clotting factors removed.     * any clear bodily fluid, see serous fluid.     * any medication derived from an animal's blood or serous fluid, often involving antibodies, such as an antidote, antivenom, or antiviral drug. commonly used as a plot device in fiction to cure someone at the last moment.   serum is the same as blood plasma except that clotting factors (such as fibrin) have been removed. blood plasma contains fibrinogen.  plasma resembles whey in appearance (transparent with a faint straw colour). it is mainly composed of water, blood proteins, and inorganic electrolytes. it serves as transport medium for glucose, lipids, hormones, metabolic end products, carbon dioxide and oxygen. (oxygen transport capacity of plasma is much lower than that of the hemoglobin in the red blood cells; it may increase under hyperbaric conditions.) plasma is the storage and transport of clotting factors and its protein content is necessary to maintain the oncotic pressure of the blood.