Vitamin Chemical Structures

Vitamins are essential nutrient which must be obtained through the diet.
Vitamins are essential nutrient which must be obtained through the diet. Seksak Kerdkanno / EyeEm / Getty Images

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
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

Vitamin B1 (Thiamine Chloride)
Vitamin B1 (Thiamine Chloride).

The B vitamins are enzyme cofactors.

Vitamin B2 (Riboflavin) Chemical Structure

Vitamin B2 (Riboflavin)
Vitamin B2 (Riboflavin). Todd Helmenstine

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

Vitamin B3 (Niacinamide)
Vitamin B3 (Niacinamide).

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 B4 (Adenine)
Vitamin B4 (Adenine).

Vitamin B5 (Pantothenic Acid) Chemical Structure

Vitamin B5 (Pantothenic Acid)
Vitamin B5 (Pantothenic Acid). Todd Helmenstine

Vitamin B6 (Pyridoxal) Chemical Structure

Vitamin B6 (Pyridoxal) Chemical Structure
Vitamin B6 (Pyridoxal) Chemical Structure Vitamin B6 (Pyridoxal) Chemical Structure. Todd Helmenstine

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

Vitamin B7 (Biotin)
Vitamin B7 (Biotin). Todd Helmenstine

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
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
Vitamin B12. Todd Helmenstine

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 or L-Ascorbic Acid
Vitamin C or L-Ascorbic Acid.

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 D2
Vitamin D2. Todd Helmenstine

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.

Vitamin D3

Vitamin D3
Vitamin D3. Todd Helmenstine

Vitamin K1 - Phylloquinone Chemical Structure

This is the chemical structure of phylloquinone.
This is the chemical structure of phylloquinone. Todd Helmenstine

The molecular formula for phylloquinone is C31H46O2. Vitamin K is synthesized by microorganisms in the digestive tract.

Vitamin K3 (Menadione) Chemical Structure

Vitamin K3 (Menadione)
Vitamin K3 (Menadione).

Vitamin K is a fat-soluble vitamin needed for the synthesis of proteins used in calcium binding in bones and for blood coagulation.

Vitamin E or Tocopherol Chemical Structure

Vitamin E or Tocopherol
Vitamin E or Tocopherol.

Vitamin E is a fat soluble antioxidant.

Vitamin M (Folic Acid) Chemical Structure

Vitamin M (Folic Acid)
Vitamin M (Folic Acid).

Vitamin U Chemical Structure

Methylmethionine is also known as Vitamin U.
Methylmethionine is also known as Vitamin U.

Vitamin H Chemical Structure

Vitamin B7 (Biotin)
Vitamin B7 (Biotin). Todd Helmenstine

The molecular formula for Vitamin H is C10H16N2O3S.