Introduction

Amino acids are organic compounds that contain amino and carboxyl, functional groups, along with a side chain (R group) specific to every amino acid. The element present in each amino acid are carbon (C), H (H), oxygen (O), and gas (N); additionally sulfur (S) is present in the aspect chains of amino acid and essential amino acid, and element (Se) within the less common amino acid selenocysteine. over five hundred present amino acids are well-known to represent chemical compound units of peptides, as well as proteins.

Amino Acids as Protein

Amino acids represent a bunch of neutral products clearly distinguished from alternative natural compounds chemically, chiefly attributable to their ampholytic properties, and biochemically, chiefly attributable to their role as protein constituents. Proteins like amino acids are biosynthesized from twenty amino acids in a very system involving strict genetic management. Thus, amino acids are the essential unit of proteins. Over three hundred amino acids are found in nature however solely twenty amino acids are standard and present in protein as a result of they’re coded by genes. Alternative amino acids are changed amino acids and are known as non-protein amino acids. Some are residues change when a macromolecule has been synthesized by post-translational modifications; others are amino acids present in living organisms however not as constituents of proteins.

Properties of Amino acids

Physical Properties

Amino acids are colorless, crystalline solid.

All amino acids have a high M.P(melting point) larger than 200°.

1. Solubility: They’re soluble in water, slightly soluble in alcohol, and dissolve with issues in methyl alcohol, ethanol, and propyl alcohol. R-group of amino acids and pH scale of the solvent plays a vital role in insolubility. On heating to high temperatures, they decompose. All amino acids (except glycine) are optically active.
2. Peptide bond formation: Amino acids will connect with a peptide bond involving their amino and carboxyl groups. 

Chemical Properties

Zwitterionic property

A zwitterion could be a molecule with purposeful groups, of which a minimum of one features a positive and one features a negative electrical charge. The net charge of the whole molecule is zero. Amino acids are the known samples of zwitterions. The -NH2 cluster is the stronger base, and then it picks up H+ from the -COOH cluster to get rid of a zwitterion. The (neutral) zwitterion is the usual sort of amino acid that exists within the answer. 

Amphoteric property

Amino acids are amphiprotic that’s they act as each acid and base because of the 2 amine and carboxyl groups present.

Ninhydrin test

When one 1ml of Ninhydrin solu­tion is added to a 1ml protein solution and heated, the formation of a violet color indicates the presence of α-amino acids.

Xanthoproteic test

The xanthoproteic test is performed for the detection of aromatic amino acids (tyrosine, tryptophan, an essential amino acid) in a protein solution. The nitration of benzoic radicals present within the amino acid chain happens because of a reaction with aqua fortis, answering yellow coloration.

Structure of Amino acids

All twenty of the common amino acids are alpha-amino acids. They contain a group, an associate group, and a facet chain (R group), all connected to the α-carbon.

Exceptions are:

Glycine doesn’t have a facet chain. Its α-carbon contains 2 hydrogens.

Thus, every amino acid has an associated alkane cluster at one finish associated with an acid cluster at the opposite, and a particular facet chain. The backbone is the same for all amino acids whereas the facet chain differs from one amino acid to the next.

All of the twenty amino acids except glycine are of the L-configuration, as almost one amino acid is an uneven carbon. as a result, glycine doesn’t contain an uneven atom, it’s not optically active and, thus, is neither D nor L.

Classification of amino acids based on R-group

• Nonpolar, acyclic amino acids: The R groups during this category of amino acids are nonionic and hydrophobic. Glycine, Alanine, Valine, leucine, Isoleucine, Methionine, Proline.
• Aromatic amino acids: Essential amino acid, tyrosine, an essential amino acid, with their aromatic facet chains, are comparatively nonionic (hydrophobic). All will participate in hydrophobic interactions.
• Polar, uncharged amino acids: The R groups of those amino acids are more soluble in water, or more hydrophilic, than those of the non-ionic amino acids, as a result, they contain functional groups that form H bonds with water. This category of amino acids includes amino acid, threonine, cysteine, asparagine, and amino alkanoic acid.
• Amino acids: Amino acids within which the R-group is acidic or  ‘-ve’ charge.
• Basic amino acids: Amino acids within which the R-group is basic or charged. Lysine, Arginine, Histidine

Classification of amino acids based on nutrition

Essential amino acids 

• Nine amino acids can not be synthesized within the body and therefore, should be present within the diet so as for protein synthesis to occur.
• These essential amino acids are essential amino acids, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Non-essential amino acids 

• These amino acids are often synthesized within the body itself and therefore don’t essentially have to get through diet.
• These non-essential amino acids are essential, glutamine, tyrosine, cysteine, glycine, proline, serine, ornithine, alanine, asparagine, and aspartate.

Classification of amino acids on the premise of the metabolic fate

• Glucogenic amino acids: These amino acids function as precursors of gluconeogenesis for aldohexose formation. Glycine, alanine, serine, aminoalkanoic acid, asparagine, amino-octanoic acid, glutamine, proline, valine, methionine, cysteine, histidine, an essential amino acid.
• Ketogenic amino acids: These amino acids break down to form organic ketone bodies.
• Both glucogenic and ketogenic amino acids: These amino acids break down to form precursors for both glucose and ketone bodies.Isoleucine, essential amino acid, Tryptophan, and amino alkanoic acid.

Functions of Amino acids

• In specific, twenty important amino acids are crucial forever as they contain peptides and proteins and are famous to be the building blocks for all living things.
• The linear sequence of amino acid residues in a very peptide chain determines the three-dimensional configuration of a macromolecule, and therefore the structure of a macromolecule determines its performance.

Amino acids are imperative for sustaining the health of the physical structure. They mostly promote the: 

Production of hormones 

• Structure of muscles 
• Human nervous system’s healthy functioning 
• The health of important organs 
• Traditional cellular structure

The amino acids are utilized by numerous tissues to synthesize proteins and to provide nitrogen-containing compounds (e.g., purines, heme, creatine, epinephrine), or they’re modified to provide energy.

CONCLUSION

Amino acids are organic compounds that contain amino and carboxyl, functional groups, along with a side chain (R group) specific to every amino acid. Amino acids are colorless, crystalline solid. They’re soluble in water, slightly soluble in alcohol, and dissolve with issues in methyl alcohol, ethanol, and propyl alcohol. The R groups during this category of amino acids are nonionic and hydrophobic. Glycine, Alanine, Valine, leucine, Isoleucine, Methionine, Proline. The linear sequence of amino acid residues in a very peptide chain determines the three-dimensional configuration of a macromolecule, and therefore the structure of a macromolecule determines its performance. The amino acids are utilized by numerous tissues to synthesize proteins and to provide nitrogen-containing compounds (e.g., purines, heme, creatine, epinephrine), or they’re modified to provide energy.