Metabolic Pathways

    Cards (39)

    • Activation energy
      Input of energy required to start a chemical reaction
    • Active site
      Region on an enzyme where the substrate binds
    • Anabolic
      Reactions that use up energy to build up large molecules from smaller ones
    • Catabolic
      Reactions that release energy in breaking down large molecules into smaller ones
    • Competitive inhibition

      Slowing of reaction rate due to the presence of a substance resembling the substrate in the active site
    • Feedback inhibition
      Enzyme inhibition caused by a critical concentration of an end product of a metabolic pathway
    • Induced fit
      Change to an enzyme's active site brought about by its substrate
    • Metabolic pathway
      Enzyme-controlled sequence of chemical reactions in a cell
    • Non-competitive inhibition
      Enzyme inhibition by a substance that binds to the enzyme at a site other than the active site and alters the shape of the active site
    • Product
      Substance resulting from an enzyme-catalysed reaction
    • Substrate
      Substance on which an enzyme works
    • Metabolism is defined as the sum of all the chemical reactions catalysed by enzymes taking place in a cell
    • Metabolic pathways are controlled pathways of reactions in cells, which are all catalysed by enzymes
    • Metabolic pathways can have reversible steps, irreversible steps and alternative routes
    • Anabolic pathways

      Large molecules built up from smaller molecules, requiring energy (ATP) from respiration (Synthesis)
    • Catabolic pathways

      Large molecules broken down into smaller molecules, releasing energy (ATP) (Degradation)
    • Metabolic pathways are controlled by the presence or absence of particular enzymes in the metabolic pathway, as well as through the regulation of rate of reaction of key enzymes within the pathway
    • Genes for some enzymes are continually expressed and therefore these enzymes are always present in the cell. They are controlled by the regulation of their rate of reaction
    • Catalysts
      Substances which speed up chemical reactions without themselves being consumed or permanently altered by the reaction
    • Activation energy
      Energy input needed to start a chemical reaction
    • Catalysts speed up chemical reactions by lowering the activation energy
    • Synthesis (building up)
      Making larger molecules from small molecules
    • Degradation (break down)

      Making smaller molecules from large molecules
    • Mechanism of Enzyme Action
      Substrate + Enzyme -> Enzyme-substrate complex -> Product(s) + Enzyme
    • Substrate
      The substance that the enzyme binds to
    • Every enzyme is specific to its substrate, meaning that for each enzyme there is only one substrate
    • Induced fit model
      • The active site of an enzyme changes shape to better fit the substrate after the substrate binds
      • The substrate molecules have a high affinity for the active site, but the subsequent products have a low affinity, allowing them to leave the active site
    • If a dynamic equilibrium is disturbed e.g., by adding substrate or removing product
      The position of equilibrium moves to counteract the change, so some metabolic reactions are reversible
    • Factors affecting enzyme activity
      • Temperature
      • pH
      • Enzyme concentration
      • Substrate concentration
    • If there is a high concentration of enzyme and substrate molecules present in a cell

      The rate of reaction will increase
    • If there is a high concentration of enzyme and a limited concentration of substrate

      The rate of reaction will not increase beyond a certain point as the substrate becomes the limiting factor
    • Effect of increasing enzyme concentration on rate of reaction
      1. Rate of reaction increases linearly with enzyme concentration when substrate is unlimited
      2. Rate of reaction reaches a plateau when substrate becomes limiting
    • Effect of increasing substrate concentration on rate of reaction
      Rate of reaction increases linearly until enzyme active sites become saturated, then rate plateaus
    • Competitive inhibition
      Inhibitors bind at the active site preventing the substrate from entering
    • If the concentration of the substrate is increased with competitive inhibition

      The rate of reaction will increase as more substrate can compete with the inhibitor for the active site
    • Non-competitive inhibition
      Inhibitors bind away from the active site but change its shape, preventing the substrate from fitting in
    • Non-competitive inhibition
      Cannot be reversed by increasing substrate concentration
    • Feedback inhibition
      The final product in the metabolic pathway reaches a critical concentration and inhibits an earlier enzyme, blocking the pathway and preventing further synthesis of the end-product
    • As the level of the end-product drops
      The inhibition on the pathway is removed and the enzyme can begin converting substrate into product again