Carboxylic acids are centrally important in biochemistry. Many important substances of oxidative metabolism are carboxylic acids, such as pyruvic acid or lactic acid.

The pH environment in which most biological processes occur is close to 7. Most carboxylic acids have ionization constants on the order of Ka = 10-5 (pKa = 5). This means that in the biochemical context, these substances exist much more prominently as their carboxylate conjugate bases.

Do you remember why you know this? The Henderson-Hasselbalch equation tells us that a weak acid with a pKa equal to 5 within a pH environment of 7 will exist 100 to 1 in the conjugate base form.

Because the more common physiological form is the carboxylate anion, biochemists much more commonly refer to 'pyruvate' and 'lactate' than to 'pyruvic acid' or 'lactic acid'.