AP Biology: Chemical Groups, Properties, Compound name, & Examples

Hydroxyl group

—OH (may be written as HO—)

Polar due to the electronegative oxygen, it forms hydrogen bonds with water and helps dissolve compounds such as sugars.

Alcohol

Ex. Ethanol

Carbonyl group

—C=O

Sugars with ketone groups are called ketoses; those with aldehydes are called aldoses.

Ketone & aldehyde

Ex. acetone and propanol

Carboxyl group

—COOH

Acts as an acid (can donate H+) because the covalent bond between oxygen and hydrogen is so polar.

Carboxylic acid, or organic acid

Ex. Acetic acid

Amino group

—NH2

Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms).

Amine

Ex. Glycine

Sulfhydryl group

—SH

Two —SH groups can react, forming a “cross-link” that helps stabilize protein structure. Hair protein cross-links maintain hair straightness or curliness; in hair salons, permanent treatments break the cross-links, then reform them while the hair is in the desired shape.

Thiol

Ex. Cysteine

Phosphate group

—OPO3^-2

Contributes a negative charge (1- when positioned inside a chain of phosphates; 2- when at the end). When attached, confers on a molecule the ability to react with water, releasing energy.

Organic phosphate

Ex. Glycerol phosphate

Methyl group

—CH3

Affects the expression of genes when on DNA or on proteins bound to DNA. Affects the shape and function of male and female sex hormones.

Methylated compound

Ex. 5-Methylcytosine