Breif overview on proteins

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  • Created by: Sania
  • Created on: 07-11-11 13:36

Proteins - The Basics

Proteins - Built up from AA there are 20 different types that are needed to make up proteins, they contain carbon,hydrogen,oxygen &nitrogen and someotimes sulphur/phosphurus. The protein structure consists of an amino group NH2 and a carboxyl group COOH. Proteins are have a crystalinne structure and are colourless. Also they are amphoteric which means that they both can react like a bas or acid as have a basic group NH2 and also a acidic group COOH and therfore when a peptide bond is formed the aa or proteins are ususally neutralised.Usually the protein is called a zwitter io as it is dipolar as is + and - and therfore carries no charge as it eqals out any charge. If we add more H+ ions to a zwitter ion then one of the O in COOH which is negative bonds with H+ to make a hydroxyl group OH. By adding more H+ conc the acidity increases with the pH and becomes more positively charged so is called an anion. Also if we have a zwitter ion and take away some H+ ions we decrease the conc of H+ ions and this increses the pH and therfore the molecule is more negatively charged and is more basic and is called a cation. Because of its amphoteric nature it can be used as a buffer - which is a chemical that will maintain a constant pH. pH depends on the concentration of H+ ions - more H+ ions means more acidic and lower pH and less H+ ions means increase in pH and therofre more basic.

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When proeteins react in a condensation reaction an amino group reats with carboxyl group resulting to a peptide bond formed and this means the compound made is named a dipeptide.If a lot dipepetides react then we end up with a polypeptide. There are 4 types of protein structures you will need to know:                                                   Primary Structure - The basic chain of AA and polypeptide chains                               Secondary Structure - This is formed by hydrogen bonding resulting to a polypeptide chain either twisitng to form an alpha helix or form a beta pleated sheet Tertiary Structure - involves the bonding and twisting of the alpha helix into a 3D shape, it does this with disulphide, ionic and hydrogen bonding                                      Quaternary Bonds - This occurs when lots of polypeptide chains which are different combine together and form big structures i.e haemoglobin usually they are involved with a non protein group i.e haemooglobin has a group called haem AKA prosthetic group                                                                                                                   Classifacation Of Proteins - There are 2 main classafacations concerning proteins - Fibrous - Insoluble, Strong, Made of main PP chains or sheets with cross linkages Globular - folded into a 3D structure into globular complex and are soluble in water

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