Vitamin Chemical Structures

Vitamins are organic molecules essential for proper metabolism that must be obtained from the diet. In some cases, an organism may be able to synthesize a small quantity of a vitamin, but in order to qualify as a vitamin, synthesis cannot fully meet metabolic needs. So, a substance that is a vitamin in one species may not be a vitamin in others. Further, a vitamin is not an essential amino acid, an essential fatty acid, or a mineral.

Most vitamins exist in multiple forms called vitamers. For example, there are at least eight forms of vitamin E, including four tocotrienols and four tocopherols.

The human body requires thirteen vitamins for metabolism: vitamin A, vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B7 (biotin), vitamin B9 (folate or folic acid), vitamin B12 (cobalamin), vitamin C (ascorbic acid), vitamin D (calciferol), vitamin E (tocopherol or tocotrienol), and vitamin K (quinone).

Several other vitamins have been proposed. Either they have been reclassified (usually as a B vitamin) or they turned out to be either nonessential or else synthesized in sufficient amounts by the body. The reason vitamin names jump from E to K is because of this reclassification.

Vitamin A (Retinol) Chemical Structure

Chemical structure of Vitamin A or Retinol.

Vitamin A regulates cell and tissue differentiation and growth. It is toxic in high doses. Humans can synthesize vitamin A from the precursor molecule beta carotene.

Vitamin B1 (Thiamine Chloride) Chemical Structure

The B vitamins are enzyme cofactors.

Vitamin B2 (Riboflavin) Chemical Structure

Riboflavin is used in many flavoprotein enzyme reactions. Medical uses include migraine prevention and strengthening the cornea of the eye. Riboflavin occurs in eggs, almonds, dairy products, green vegetables, meat, and mushrooms.

Vitamin B3 (Niacinamide) Chemical Structure

Niacin is also known as niacinamide or the related compound nicotinic acid. The body can synthesize niacin from the amino acid tryptophan. It is found in tuna, fortified foods, turkey, pork, venison, mushrooms, and some vegetables.

Niacin and nicotinamide are precursors of the coenzymes NAD and NADP, which are used in hydrogen transfer processes in cells, catabolism of nutrients, and cholesterol synthesis.

Vitamin B4 (Adenine) Chemical Structure

Vitamin B5 (Pantothenic Acid) Chemical Structure

Vitamin B6 (Pyridoxal) Chemical Structure

Vitamin B6 is essential as a coenzyme in about 100 enzyme reactions, including those involved in lipid, amino acid, and glucose metabolism. It occurs in grains, meat, fortified cereals, dark chocolate, pistachios, and potatoes.

Vitamin B7 (Biotin) Chemical Structure

Biotin may be obtained from food (cooked eggs, yeast, peanuts, avocado), plus gut organisms synthesize it for absorption into the bloodstream. This water-soluble vitamin is used in fat, amino acid, and carbohydrate metabolism. Biotin deficiency typically causes a skin rash and thinning hair.

Vitamin B9 - Folic Acid

Folic acid (vitamin B9) molecule. LAGUNA DESIGN / Getty Images

Folic acid is a water soluble vitamin. It is used to make DNA and RNA and for amino acid metabolism. Deficiency is associated with anemia and neural tube defects in human development. Children exhibit signs of folic acid deficiencies within a month of eating a poor diet. The vitamin is abundant in green, leafy vegetables.

Vitamin B12 Chemical Structure

Vitamin B12 is a water soluble vitamin integral to DNA synthesis, fatty acid synthesis, and amino acid metabolism. It is important for nerve myelination and red blood cell maturation.

Vitamin C - Ascorbic Acid Chemical Structure

Vitamin C is a water-soluble antioxidant. It is used to produce neurotransmitters, support immune system function, and repair tissue.

Vitamin D2 Chemical Structure

Vitamin D acts like a hormine. It regulates mineral metabolism and is needed for proper bone and organ health. Skin cells can synthesize vitamin D upon exposure to ultraviolet light from the Sun.