Which group do the amino acids E belong to?

The amino acid represented by the letter E is glutamic acid, which is classified as a negatively-charged amino acid. This classification is due to the presence of a carboxylic acid side chain, specifically a second carboxyl group (-COOH) in its structure. At physiological pH, the side chain's carboxyl group ionizes to release a hydrogen ion (H+), resulting in a negatively charged side chain.

Negative charges in amino acids play significant roles in protein structure and function, particularly in interactions with other molecules and ions in biological systems. This ionization allows glutamic acid to participate actively in biochemical processes, such as enzyme catalysis and molecular recognition.

In contrast, the other classifications do not accurately encompass glutamic acid's properties. While glutamic acid does have polar characteristics due to its charged side chain, it is chiefly recognized for its negative charge at physiological pH, further solidifying its classification in the negatively-charged group.