functional groups

hydroxyl group

—OH; polar; forms hydrogen bonds w/ water

carbonyl group

C=O; polar; important in sugars

carboxyl group

—COOH; donates H⁺ → acts as an acid; often negatively charged

amino group

—NH₂; accepts H⁺ → acts as a base; can be positively charged

sulfhydryl group

—SH; disulfide bonds; protein stability

phosphate group

—PO₄; important in ATP and energy transfer; negative charge

methyl group

—CH₃; nonpolar; shape, recognition, regulation

which functional groups are polar?

hydroxyl, carbonyl, sulfydryl

which functional group is nonpolar?

methyl

which functional groups are often charged?

carboxyl, amino, phosphate