Topic 8 - HL Extensions

• Metabolic pathways


  Series of small, enzyme-catalysed reactions that involve a chemical change
• Metabolic pathways


  • Can be chain reactions with a distinct start and end
  • Can be cyclic with the end product feeding back into the starting reactant
• Metabolites/Intermediates


  Chemicals involved in metabolic pathways
• Enzymes


  Biological catalysts that speed up the rate of chemical reactions without being consumed or permanently altered

  
• Enzyme-catalysed reaction


  1. Substrate binds to active site of enzyme

  2. Enzyme-substrate complex forms

  3. Product is formed

  4. Enzyme is released

  
• Activation energy


  Energy needed for a reaction to occur
• Enzymes


  Lower the activation energy required for a reaction
• Endergonic reaction


  Reaction that absorbs energy from the surroundings
• Exergonic reaction


  Reaction that releases energy to the surroundings
• Enzyme inhibitors


  • Competitive - bind to active site and compete with substrate
  • Non-competitive - bind to other site and change shape of active site

  
• Competitive inhibitor


  • Oxygen inhibiting RuBisCO in photosynthesis
• Non-competitive inhibitor


  • Cyanide inhibiting cytochrome c oxidase in respiration

  
• Allosteric site


  Site on enzyme away from active site where allosteric regulators can bind

  
• Allosteric inhibition


  End product binds to allosteric site and inhibits the enzyme, preventing build-up of intermediates

  
• Bioinformatics is the use of computers to analyse and sequence data in biological research
• Bioinformatics has facilitated research into metabolic pathways
• Chemogenomics focuses on finding chemicals that target enzyme binding sites to alter metabolic pathways

  
• Bioinformatics has been used to screen chemicals against malarial enzymes to identify potential inhibitors
• Bioinformatics has also been used to develop new anti-malarial drugs through chemical modification and screening databases
• Calculating rates of reaction

  Measure rate of disappearance of substrate or rate of product accumulation over time

  
• Bioinformatics


  • It has played a key role in developing new treatments for malaria, including:
  • Chemical modification of current anti-malarial drugs to create hybrid drugs
  • Screening databases for new compounds with potential anti-malarial activity
• 15 new chemicals have been identified that bind to 61 malarial proteins creating new lines of investigation for scientists to follow in the search for anti-malarials
• Rate of reaction


  The rate of disappearance of a substrate or the rate of product accumulated in a given time period
• Calculating the rate of reaction


  1. Measure the change in quantity (usually volume or mass) of substrate or product over a measured time period

  2. If cannot collect quantitative data, calculate the rate of reaction based on the time measured using the equation: 1 ÷ time taken (seconds) and should include the units s⁻¹

  
• High rate of reaction


  The reaction happens in less time i.e. it is faster
• Low rate of reaction


  The reaction happens in more time i.e. it is slower
• As the reaction proceeds


  The rate of reaction is likely to change as the substrate concentration will decrease
• Plotting the rate of reaction

  1. Graph the reaction time on the X-axis and the quantity of product or substrate on the Y-axis

  2. The steeper the line, the faster the rate of reaction

  3. Calculate the gradient from a point on the graph to measure the rate of reaction at that point in time

  
• Competitive inhibitor


  • Lowers the initial rate of reaction (by occupying some of the available active sites), whilst the maximal rate is not affected
  • Eventually, the same amount of product will be produced as would have been produced without the competitive inhibitor

  
• Non-competitive inhibitor


  • Lowers the initial rate of reaction and the maximal rate of reaction
  • A lower amount of product is produced than would normally be produced
• Oxidation


  The loss of electrons
• Reduction


  The gain of electrons
• Redox reactions


  Involve the transfer of electrons between molecules
• Reducing agents


  Molecules that have a strong tendency to lose/donate their electrons
• Oxidising agents


  Molecules that have a strong tendency to gain electrons
• Oxidation is the loss of hydrogen, gain of oxygen and releases energy to the surroundings (exergonic)
• Reduction is the gain of hydrogen, loss of oxygen and absorbs energy from the surroundings (endergonic)
• NAD+


  The primary electron carrier involved in respiration
• FAD


  Another electron carrier used in respiration
• Phosphorylation


  1. The addition of a phosphate ion to a molecule

  2. Makes the molecule less stable and therefore more likely to react

  3. Activates a molecule by making it more reactive