Final answer:
At physiological pH, glutamic acid loses a proton from its carboxyl side chain, becoming negatively charged and capable of forming ionic interactions with basic amino acids; it may also undergo oxidative deamination, resulting in the formation of ammonium ions or urea for nitrogen excretion.
Step-by-step explanation:
When glutamic acid is at physiological pH, which is around 7.4, it exists mainly in its anionic form due to the deprotonation of its side chain carboxyl group. The side chain of glutamic acid has a pKa around 4.1, which means it will lose a proton and become negatively charged at physiological pH. This transformation allows it to form ionic interactions with basic amino acids like arginine, lysine, or histidine. Glutamate can also undergo oxidative deamination, where it loses its amino group to form an ammonium ion or is processed further to form urea, which is the main form for excretion of excess nitrogen.