Amino acids are the basic building units of proteins.Their molecule posses both an amino group as well as a carboxylic group. The amino acids having amino and carboxyl group attached to the same carbon, i.e., alpha-carbon atom is called as alpha-amino acids. Example: Glycine , Alanine etc.
Rules for nomenclature of amino acid
Amino acids are generally known by their common names. In IUPAC system each amino acid has been given standard abbreviation or a code which usually consists of first three letters of the common name. For example, glycine is given the code ala. Sometimes one letter symbol is also used. For example, glycine is represented by G and alanine by A.
The amino acid containing one -NH2 and one COOH groups, are called neutral amino acids. Example: Alanine.
Acidic amino acids
The amino acids containing two -COOH groups and one -NH2 group are called acidic amino acids.For example, aspartic acid, glutomic acids.
Basic amino acids
The amino acids containing two −NH2 groups and one −COOH group are called basic amino acids. Some examples of basic amino acids are lysine, arginine.
Essential and non-essential amino acids
The amino acids which human body can not synthesize and must be supplied in the diet are called essential amino acids. Example, Valine, leucine etc. The amino acids which are synthesized by the human body are termed as non-essential amino acids. Example, Glycine.
Physical properties of alpha-amino acids
The important physical properties of alpha-amino acids are as follows. 1) Amino acids are usually colorless, crystalline solids with high melting point 2) They are soluble in water. The aqueous solution is neutral and shows amphoteric behavior
Chemical properties of amino acids
Alpha-amino acid contain both amino as well as acidic group .They form salts with acids as well as with base.
Zwitter ion prepared by loss of proton by acidic carboxyl group which is taken up by the basic amino group in alpha-amino acids. Zwitter ion is neutral but contains both positive and negative charges. Due to its dipolar nature it is referred to as a dipolar ion.
Define and give examples of peptide bond
The bond formed by condensation of amino acid molecules is called as peptide bond or peptide linkage.