Vitamin B12.ppt

Vitamin B12 made by 唐淑妍 柯美强 郑刘彬 Vitamin B12 Functions Abtract Struture Source Deficiency Abstract Vitamin B12, also called cobalamin(钴胺素), is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is normally involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid synthesis and energy production. The vitamin is the largest and most structurally complicated, and the only vitamin containing major mineral. In a broad sense, B12 refers to a group of cobalt-containing vitamer compounds known as cobalamins. The term B12 may be properly used to refer to cyanocobalamin(氰钴胺), the principal B12 form used for foods and in nutritional supplements. Structure Molecular formula:C63H88CoN14O14P The structure of B12 is based on a corrin(咕啉) ring. The central metal ion is cobalt(钴). Four of the six coordination sites are provided by the corrin ring, and a fifth by a dimethylbenzimidazole（二甲基苯并咪唑） group.The sixth coordination site, the center of reactivity, is variable, being a cyano group , a hydroxyl group , a methyl group or a 5‘-deoxyadenosyl group. The three-dimensional structure of vitamin B12 Cyanocobalamin(氰钴胺) is one such vitamer in this B complex, because it can be metabolized in the body to an active co-enzyme form. Since the cyanocobalamin form of B12 is easy to crystallize and is not sensitive to air-oxidation, it is typically used as a form of B12 for food additives. Pure cyanocobalamin possesses the deep pink color and the crystals are well formed and easily grown up to millimeter size. Hydroxocobalamin(羟钴胺) is commonly encountered in pharmacology(药理学), but which is not normally present in the human body. It is produced by bacteria. It is sometimes denoted B12a. Hydroxocobalamin has an avid affinity for cyanide(氰) ion and has been used as an antidote(解毒剂) to cyanide pois