Amino acids contain amino (–NH₂) and carboxyl (–COOH) functional groups. Depending upon the relative position of amino group with respect to carboxyl group, the amino acids can be classified as α, β, γ, δ and so on. Only α-amino acids are obtained on hydrolysis of proteins. They may contain other functional groups also. All α-amino acids have trivial names, which usually reflect the property of that compound or its source. Glycine is so named since it has sweet taste (in Greek glykos means sweet) and tyrosine was first obtained from cheese (in Greek, tyros means cheese.) Amino acids are generally represented by a three letter symbol, sometimes one letter symbol is also used. Amino acids are classified as acidic, basic or neutral depending upon the relative number of amino and carboxyl groups in their molecule. Equal number of amino and carboxyl groups makes it neutral; more number of amino than carboxyl groups makes it basic and more carboxyl groups as compared to amino groups makes it acidic. The amino acids, which can be synthesized in the body, are known as nonessential amino acids. On the other hand, those which cannot be synthesized in the body and must be obtained through diet, are known as essential amino acids.

In which amino acid Imidazole group are found?

Histidine

The correct answer is option 3. Histidine.

Out of the options provided, the amino acid containing the imidazole group is histidine.

Here's why:

Imidazole group: This is a five-membered aromatic ring containing two nitrogen atoms. It plays a crucial role in several biological processes due to its unique properties, including acting as a proton acceptor and participating in hydrogen bonding.

Lysine: This amino acid features a side chain with an ammonium group \((-NH_3^+)\) but doesn't possess the characteristic five-membered imidazole ring.

Arginine: Although containing a five-membered ring in its side chain, it's a guanidinium group, distinct from the imidazole structure.

Glutamate: This amino acid has a side chain with a carboxylic acid group, lacking the characteristic features of an imidazole group.

Therefore, based on the presence of the unique imidazole ring, histidine stands out as the only amino acid among the options with this functional group.