Enzymes

• What are Enzymes

  Biological catalysts that speed up chemical reactions.
• Structure

  -have an active site with a specific shape where the substrate (the substance that the enzyme interacts with) molecules bind to

  -highly specific due to their tertiary structure
• How do enzymes speed up reactions

  Enzymes lower the activation energy required to begin the chemical reaction which speeds up the rate of reaction

  
• Why do enzymes lower the activation energy

  -Attaches two substrates that need to be joined to reduce any repulsion between the molecules so they can bond more easily.

  -Enzyme puts a strain on bonds in a substrate of a breakdown reaction, so the substrate molecule breaks up more easily and the breakdown reaction is catalysed
• 'Lock and Key' Model


  Enzyme's active site and the substrate have a complementary shape

  
• 'Induced Fit' Model


  Enzymes only bond to a particular complementary substrate that will change the shape of the active site to fit

  
• Enzyme Properties

  -Enzyme properties are related to their tertiary structure

  -Only catalyse one reaction as only one complementary substrate will fit into the active site

  -Active site's shape is determined by the enzyme's tertiary structure (which is determined by the enzyme's primary structure)

  
• Tertiary Structure of an Enzyme

  -altering the tertiary structure of a protein will change the shape of the active site and prevent future reactions from happening as enzyme-substrate complex won't be able to form

  -this may be due to altered changes in pH or temperature
• Primary Structure of an Enzyme

  -the primary structure (amino acid sequence) of a protein is determined by a gene.

  -a mutation in that gene could change the tertiary structure of the enzyme produced