What is the primary distinction between aspartate and aspartic acid?

Aspartate is indeed the conjugate base of aspartic acid. To understand this distinction, it is essential to look at the protonation state of the molecule under physiological pH conditions.

Aspartic acid is an amino acid with a side chain carboxyl group (-COOH) that can donate a proton (H+) when it is in an acidic environment, thus becoming negatively charged at physiological pH (around 7.4). When this carboxyl group loses a proton, it transforms into aspartate, which is negatively charged due to the presence of a carboxylate group (-COO⁻). This means that under physiological conditions, aspartate is the predominant form found in the body, and it exists as the deprotonated form of aspartic acid.

This relationship underscores the importance of the pH in determining the state of amino acids, as they can exist in both protonated and deprotonated forms. Understanding this concept is crucial in biochemistry, especially when considering the behavior of amino acids within proteins and metabolic pathways.