A bottle of B-complex vitamin pills

Substance that may be converted within the body to a vitamin.

- Provitamin

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Organic molecule that is an essential micronutrient which an organism needs in small quantities for the proper functioning of its metabolism.

A bottle of B-complex vitamin pills
Calcium combined with vitamin D (as calciferol) supplement tablets with fillers.
Jack Drummond's single-paragraph article in 1920 which provided structure and nomenclature used today for vitamins

Some sources list fourteen vitamins, by including choline, but major health organizations list thirteen: vitamin A (as all-trans-retinol, all-trans-retinyl-esters, as well as all-trans-beta-carotene and other provitamin A carotenoids), vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B7 (biotin), vitamin B9 (folic acid or folate), vitamin B12 (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (phylloquinone and menaquinones).


Organic, strongly coloured red-orange pigment abundant in fungi, plants, and fruits.

Methane, CH4; is among the simplest organic compounds.

Plant carotenoids are the primary dietary source of provitamin A worldwide, with β-carotene as the best-known provitamin A carotenoid.


Sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells.

The gonane skeleton, with the IUPAC recommended numbering of the carbon atoms

In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2.

Vitamin A

Fat-soluble vitamin and an essential nutrient for humans.

Typical location of Bitot's spots
Carrots are a rich source of beta-carotene
Vitamin A supplementation coverage rate (children ages 6–59 months), 2014
Retinoids: Tretinoin is all-trans-retinoic acid; initial tradename: Retin-A. Isotretinoin is 13-cis-retinoic acid; initial tradename: Accutane. Etretinate and Acitretin, its non-esterified metabolite, are used orally to treat severe psoriasis.
Vitamin A biosynthesis from β-carotene
β-ionone ring
Frederick Gowland Hopkins, 1929 Nobel Prize for Physiology or Medicine
George Wald, 1967 Nobel Prize for Physiology or Medicine

It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably beta-carotene [β-carotene]).


Vitamins occur in a variety of related forms known as vitamers.

A bottle of B-complex vitamin pills

For example, vitamin A is the generic descriptor for the class of vitamin A vitamers which include retinol, retinal, retinoic acid, and provitamin carotenoids such as beta-carotene among others.


Bepanthen eye and nose ointment (Germany)

Panthenol (also called pantothenol) is the alcohol analog of pantothenic acid (vitamin B5), and is thus a provitamin of B5.


Natural organic compound with the formula C6H42C2H(CH3).

The menadione core is apparent in the structure of vitamin K.

The compound is variously known as vitamin K3 and provitamin K3.


The epidermal strata of the skin.

7-Dehydrocholesterol (7-DHC) is a zoosterol that functions in the serum as a cholesterol precursor, and is photochemically converted to vitamin D3 in the skin, therefore functioning as provitamin-D3.


Natural carotenoid pigment.

The orange ring surrounding Grand Prismatic Spring is due to carotenoid molecules, produced by mats of cyanobacteria and other bacteria.

In the human body, β-cryptoxanthin is converted to vitamin A (retinol) and is, therefore, considered a provitamin A.

Nutrition and cognition

Immense amount of energy in comparison to the rest of the body.

The brain of a common chimpanzee

Vitamin A is an essential nutrient for mammals which takes form in either retinol or the provitamin beta-Carotene.