Choline is a water-soluble vitamin-like essential nutrient. It is a basic constituent of lecithin, which is present in many plants and animal organs. The term cholines refers to the class of quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation (X on the right denotes an undefined counteranion).
The cation appears in the head groups of phosphatidylcholine and sphingomyelin, two classes of phospholipid that are abundant in cell membranes. Choline is the precursor molecule for the neurotransmitter acetylcholine, which is involved in many functions including memory and muscle control.