OXIDATION
Properly the word oxidation means bonding of a substance with oxygen. Oxygen, being one of the most active chemical elements, more or less strenuously reacts nearly with all the rest of the elements. Oxidation, which proceeds with emission of a great amount of warmth and light, is usually called burning. Slowly proceeding oxidation processes, depending on the character of oxidizing agent, can be called corrosion (for iron), smolder (for organic substances), or, more often, just oxidation.
Oxidation of molecules in a cell proceeds not in one stage, like, for example, in burning. Molecules have to pass through a large numver of reactions, and only in few of them direct ajoining of the oxygen takes place. Oxidation in this case is not limited only to ajoining of an oxygen atom; this term has more general character and is applicable to any reaction, in which electrons transfer from one atom to another. In this sense, removing of electrons can be called oxidation, and ajoining of electrons – reduction.