Numerous patterns of atoms and bonds exist in organic compounds. These configurations of atoms are called functional groups, as each has specific, predictable properties. For example, the carboxyl functional group (symbolized as COOH) has both a carbonyl and a hydroxyl group attached to the same carbon atom, resulting in new properties. Hydroxyl functional groups have one hydrogen linked to one oxygen atom (symbolized as -OH). These groups readily form hydrogen bonds (which is why certain molecules are soluble in water); for example, alcohols and sugars are full of hydroxyl groups.