Question

Guanidino is present in the amino acid

Answer 1

The answer is an essential amino acid that is physiologically active in L form. It has the molecular formula ${{C}_{6}}{{H}_{14}}{{N}_{4}}{{O}_{2}}$. Molecular weight is 174.2 $gmo{{l}^{-1}}$ .

Complete step by step solution:
-As we know amino acids are called building blocks of proteins. As we are aware ,they are a group of organic molecules consisting of a basic amino group ($Nu {{Eta }_{2}}$), an acidic carboxyl group ($-COOH$) along with an organic group R( or side chain) which is unique to each amino acid .
- Guanidine is a compound with the molecular formula $HNC{{(N{{H}_{2}})}_{2}}$. It gets dissolved in the polar solvents and it’s a colourless solid. Guanidine is a strong base and is found in urine as a result of the protein metabolism.
- As we mentioned guanidine is a nitrogen organic base and is widely used in the synthesis of heterocyclic compounds incorporating at least two nitrogen atoms.
- The structure of the guanidino group can be easily thought of as a nitrogenous analogue of the carbonic acid functional group. That is, in guanidine the $C=O$ group in carbonic acid is replaced by a $C=NH$group and each $OH$ is replaced by a $N{{H}_{2}}$ group.
- The guanidine moiety or guanidino functional group appears in larger organic molecules such as on the side chain of the amino acid arginine. Arginine, an essential amino acid, contains a positively charged Guanidino functional group in its side chain.
- Arginine is an $\alpha$-amino acid which is mainly used in the biosynthesis of proteins. This amino acid contains an $\alpha$-amino group, an $\alpha$-carboxylic acid group and also a side chain that consists of a 3-carbon aliphatic straight chain ending in a guanidino functional group
- The guanidino functional group that is present in the side chain of the amino acid arginine plays a major role in the interaction with the enzymes or receptors through hydrogen bonding and electrostatic force of attraction.
-The structures of guanidino group and arginine amino acid are given below

Therefore, the answer is Arginine. Guanidino group is present in the amino acid arginine.

Note: Do not confuse guanidine with guanine or guanosine. Guanine is a nucleobase that is found in genetic materials such as DNA and RNA whereas guanosine is a purine nucleoside comprising guanine attached to a ribose ring via a glycosidic linkage.