Biological molecules 1

• What is an amino acid made up of?

  Amino group, R group and carboxyl group.
• How is a dipeptide formed?

  A condensation reaction between 2 amino acids produces a dipeptide.

  Held together by peptide bonds.
• Polypeptide/primary structure of proteins:


  A condensation reaction between amino acids with many peptide bonds between each amino acid.

  This is the primary structure of a protein; the order of the amino acids in this chain will determine the final structure and the function of the protein.

  A change to the amino acid sequence will change the structure and function of a protein.
• Secondary structure of proteins:

  Polymer of amino acids,

  Joined by peptide bonds,

  Formed by condensation,

  Primary structure is order of amino acids,

  Secondary structure is folding of polypeptide chains due to hydrogen bonding.
• Tertiary structure of protein:

  Polymer of amino acids,

  Joined by peptide bonds,

  Formed by condensation,

  Primary structure is order of amino acids,

  Secondary structure is folding of polypeptide chain due to hydrogen bonding,

  Tertiary structure is further twisting and folding due to ionic bonds and disulphide bridges.
• Quaternary structure:


  Proteins composed of more than one polypeptide chain,

  often with a prosthetic group e.g haem,

  Haemoglobin
• Enzymes:

  Have a specific tertiary structure - gives them a specific active site,

  Active site is only complementary to only one substrate,

  Substrate initially is not complementary to the active site,

  As the substrate approaches the active site there is an attraction causing the bending of bonds,

  Acts as a catalyst so lowers the activation energy of the reaction,

  Shape of the active site changes as the enzyme-substrate complex forms
• Competitive inhibition:


  Competitive inhibitor - have a similar shape to the substrate and are able to bind to the active site,

  This stops the substrate binding and prevents enzyme-substrate complexes forming.
• Non-competitive inhibitor:


  Non-competitive inhibitor binds to the site away from active site,

  This causes a conformational change in the enzymes tertiary structure and the active site changes shape,

  The substrate is no longer complementary to the active site an enzyme-substrate complexes are no longer able to form