To clarify the statements regarding amino acids:

Chirality in Amino Acids: Most naturally occurring amino acids contain at least one chiral center, but there are exceptions. For example, Isoleucine has two chiral centers, and Glycine is an exception as it is optically inactive due to lacking a chiral center.

Cysteine and Dimerization: The amino acid Cysteine can easily undergo dimerization. This is due to its free sulfhydryl (SH) group, which can form disulfide bonds, leading to the formation of a dimer.

Carboxyl Groups in Amino Acids: Glutamic acid is not the only amino acid with a carboxyl group in its side chain. Aspartic acid also contains a carboxyl group in its side chain.

Optical Activity: While many naturally occurring amino acids are indeed optically active, Glycine is an exception as it does not possess a chiral center and is hence optically inactive.

In summary:

Not all naturally occurring amino acids are optically active (e.g., Glycine).

Not all naturally occurring amino acids contain only one chiral center (e.g., Isoleucine has two).

Both Glutamic acid and Aspartic acid contain side chain carboxyl groups.

Cysteine can dimerize due to its SH group.