vitamin

Vitamins are a group of small molecular weight organic compounds that have a vital function in the metabolism of organisms. Viewed from the side enzimologi (the science of enzymes), vitamins are cofactors in Vitamins are chemical reactions catalyzed by enzymes. The term "vitamin" actually not appropriate to wear but ultimately retained in the context of health science and nutrition. The name comes from the combination of the Latin word vita, which means life and amines (amine) which refers to an organic group which has a nitrogen atom (N), because initially vitamin considered so. Later in mind that many vitamins do not have atomic N.
As one of the components of nutrition, vitamins necessary to facilitate the body's metabolism, and not functioning to produce energy. Vitamins are involved in enzymatic processes. The body needs vitamins in small amounts, but if it needs a little overlooked, would lead to disruption of metabolism in our bodies because its function can not be replaced by another compound. Vitamin deficiency condition called avitaminosis.
In general, vitamins can not be made by animals (or humans) because they do not have the enzymes to form it, so it must be supplied from food. However, there are some vitamins that can be made from certain substances (called provitamin) in the body. Examples of vitamins which have provitamin is vitamin D. Provitamin D numerous in the subcutaneous tissue. Other vitamins that disintetis in the body is vitamin K and vitamin B12. Both kinds of vitamins are disintetis in the gut by bacteria.
Based on the solubility of vitamin divided into two groups, namely water-soluble vitamins (vitamins C and all groups of vitamin B) and fat-soluble (vitamins A, D, E, and K). Because of these solubility properties, water-soluble vitamins can not be stored in the body, while fat-soluble vitamins can be stored in the body.
These are compounds that are categorized as natural vitamins. 
Vitamin A 
Vitamin B12
Vitamin C 
Vitamin D 
Vitamin E 
Vitamin K