CoachThe organic molecules of the cell are carbon skeletons bearing a small set of functional groups that determine their chemistry:
| group | formula | property | found in |
|---|---|---|---|
| hydroxyl | polar, H-bonding | sugars, alcohols | |
| carbonyl | polar, reactive | aldoses, ketoses | |
| carboxyl | acid (p) | fatty acids, amino acids | |
| amino | base (p) | amino acids | |
| phosphate | charged, energy-rich links | nucleotides, ATP | |
| sulfhydryl | forms S–S bridges | cysteine | |
| methyl | non-polar | lipids, DNA marks |
At the pH of the cell carboxyl groups are ionised () and amino groups protonated ().