- Alcohols (-OH): a hydroxyl group attached to a carbon atom

- Aldehydes (-CHO): a carbonyl group attached to a hydrogen atom

- Ketones (-CO-): a carbonyl group attached to two carbon atoms

- Carboxylic acids (-COOH): a carboxyl group consisting of a carbonyl group and a hydroxyl group

- Esters (-COO-R): a carboxyl group where the hydrogen atom is replaced by an alkyl group

- Amides (-CONH2): a carboxyl group where the hydroxyl group is replaced by an amino group

- Amines (-NH2): an amino group attached to a carbon atom

- Sulfhydryl groups (-SH): a thiol group consisting of a sulfur atom attached to a hydrogen atom

- Disulfide bonds (-S-S-): two sulfur atoms bonded together

- Phosphate groups (-PO4-): a phosphate group consisting of a phosphorus atom bonded to four oxygen atoms