proteins

• what are proteins made up of?

  are made up of one or more polymers, which are made up of monomers called amino acids
• what are amino acids made up of?

  a central carbon. hydrogen, an amino group, a carboxyl group and a side group
• what is a peptide bond?

  a bond between two amino acids, formed by a condensation reaction.
• If a peptide bond is formed between just two amino acids, what do we call the resulting molecule?

  dipeptide
• If peptide bonds are formed between lots of amino acids, what do we call the resulting molecule?


  polypeptide (chain)
• If polypeptides combine with other polypeptides, what do we call the resulting molecule?

  protein
• what is the primary structure of a protein?

  sequence of amino acids in the polypeptide chains
• what is the secondary structure of a protein?

  The folding of a polypeptide chain into an alpha helix or a beta pleated sheet.
• why does the folding of the secondary structure happen?

  hydrogen bonds form between the groups of peptide bonds
• what is the tertiary structure of a protein caused by?

  bonds between the side groups of amino acids
• what is the tertiary structure of a protein?

  3D folding of the whole polypeptide chain
• what do we call the non-protein part in a protein?

  prosthetic group e.g. haem group. if a protein contains a prosthetic group it is called a conjugated protein
• what is the quaternary structure of a protein made up of?

  2 or more polypeptide chains join together
• Which bonds are easily broken by changes in?

  hydrogen and ionic bonds
• what can changes in acidity lead to?

  The breaking of ionic and hydrogen bonds found within proteins.This can trigger a change in the tertiary structure of the protein.
• It is possible to change a protein’s structure by changing the pH around it.How is this done?

  • adding acid to the solution to make more protons (H+)(H+) available.
  • adding alkali to the solution would reduce the availability of protons.
• Biuret test

  1. Add some of the food sample to a test tube and add an equal volume of sodium hydroxide solution.
  2. Add a few drops of copper sulfate solution to the test tube and mix gently.
• what is a positive result for the biuret test indicated by?

  a purple colour
• State the biochemical test you would use to confirm the presence of amylase in a sample.

  To test for amylase, which contains amino acids, we use the biuret test to detect peptide bonds. The positive test colour for this is purple.