• Proteins contain carbon, hydrogen, nitrogen, sulphur and sometimes phosphorous. Proteins are large molecules formed from the combination of number of simple substances known as amino acids, the building blocks.
  • Structure of protein (Primary structure, secondary structure, tertiary structure and quaternary structure)
  • Proteins are large molecules formed by the combination of a number of amino acids. About 21 amino acids have been found to occur in proteins they are listed below.
Primary structure

Secondary structure

Tertiary and Quaternary structure

  1. Mono amino – mono carboxylic acids. These include glycine, alanine, valine, leucine, isoleucine, moleucine, serine and threonine.
  2. Mono amino – dicarboxylic acids. These include aspartic acid and glutamic acid.
  3. Diamino – monocarboxylic acids. Arginine and lysine belong to this group.
  4. Sulphur containing amino acids. These are cystine, cysteine and methionine
  5. Aromatic and heterocylic amino acids. These include phenylalanine, tyrosine, histidine, tryptophan and hydroxy proline.
The main type of linkage between the amino acids in the protein molecule is the peptide bond.
Poly - Peptide
When proteins are heated, decrease in their solubility is observed. This is known as denaturation.
Last modified: Saturday, 2 June 2012, 6:03 AM