Fatty acids (or as their salts) do not often occur as such in biological systems.

Gluconic acid occurs naturally in fruit, honey, kombucha tea, and wine.

Hyaluronic acid (HA) naturally occurs, and is identical, in all animals.

Other carboxylic acids occur in many living systems.

Formic acid occurs widely in nature as its conjugate base formate.

Benzoic acid occurs naturally as do its esters in many plant and animal species.

Angelic acid occurs in the roots of many plants, especially of the family Apiaceae.

Straight-chain fatty acids occur in two types; saturated and unsaturated.

Fatty acids do not occur as such in milk (and rarely in any food).

The acid is not stable and only occurs as an intermediate; for example, in the oxidation of hypobromites.