∞ generated and posted on 2016.12.18 ∞
Oxygen that is single bonded to a carbon and single bonded to a hydrogen atom (and where a carbonyl group is not also bonded to the carbon atom).
Hydroxyl groups define alcohols, are found in the R groups of some amino acids, and are a substantial presence in both carbohydrates and the molecule glycerol (which is one of the bases of triglycerides).
Figure legend: Shown are three representations of hydroxyl groups, creating various alcohols, with single bonds indicated using either dashes or colons. Not all bonds are shown and the radical group shown at the top must be a carbon-containing group, particularly as attached to the hydroxyl group, that is, it cannot be a hydrogen since otherwise what would be shown is water rather than an alcohol.
See also hydroxy group as, apparently, a quasi synonym.