2.1 - metabolic pathways

• Define cell metabolism?

  the total of all integrated and controlled enzyme-catalysed reactions that occur within a cell
• What is a reversible step in a metabolic pathway?

  one where the product can be converted back into the reactant
• what is an irreversible step in a metabolic pathway?

  where the reactant can only be converted into the product
• what is an alternative route?

  allow steps in the pathway to be bypassed
• define a catabolic reaction?

  breaking down large molecules into smaller molecules, releasing ATP
• define an anabolic reaction?

  building up large molecules from small molecules, requiring ATP
• the energy produced from catabolic reactions can be used in anabolic reactions
• both catabolic and anabolic reactions can have reversible/irreversible steps and alternative routes
• what is the cell membrane?

  a boundary that separates intracellular environment from extracellular environment to ensure it controls what enters or exits the cell
• what is the plasma membrane made up of?

  phospholipid bilayer and proteins
• what are the 3 types of membrane protein?

  • pores
  • pumps
  • enzymes
• define activation energy?

  the minimum kinetic energy required for the colliding particles to form an activated complex
• how do enzymes speed up reactions?

  lower the activation energy
• the substrate has high affinity for the active site
• the product has low affinity for the active site
• what is induced fit?

  after the substrate has bound to the active site, the active site changes shape to better fit the substrate
• 4 factors affecting enzyme activity?

  • substrate concentration
  • product concentration
  • pH
  • temperature
• Why does the graph level off?

  all active sites are occupied due to high substrate concentration

  
• Reversible/irreversible?

  reversible if substrate concentration is increased

  
• Reversible/irreversible?

  irreversible

  
• What is a competitive inhibitor?

  molecule that binds to the active site to prevent the substrate from binding
• what is a non-competitive inhibitor?

  binds to an allosteric site and permanently changes the shape of the active site
• define feedback inhibition?

  where the end product in a metabolic pathway reaches a critical concentration, so inhibits an earlier enzyme and prevents further synthesis of end product
• feedback inhibition saves ATP