1.6 Metabolic Pathways

• What are metabolic pathways?

  Integrated and controlled enzyme-catalysed reactions
• What types of steps can metabolic pathways have?

  Reversible steps, irreversible steps, alternative routes
• What are the two types of reactions in metabolic pathways?

  Anabolic and catabolic reactions
• What do anabolic reactions do?

  Build up large molecules from small molecules
• What is required for anabolic reactions?

  Energy
• What do catabolic reactions do?

  Break down large molecules into smaller molecules
• What do catabolic reactions release?

  Energy
• How are metabolic pathways controlled?

  By the presence of enzymes and reaction rates
• What is induced fit in enzyme activity?

  Active site changes shape to fit substrate
• What is the affinity of substrate molecules for the active site?

  High affinity
• What is the affinity of subsequent products for the active site?

  Low affinity
• What is activation energy?

  The energy needed for a reaction to occur
• How does an enzyme affect activation energy?

  It lowers the activation energy

  
• How can substrate or product concentration affect metabolic reactions?

  They can drive reactions in a particular direction
• What do competitive inhibitors do?

  Bind at the active site, blocking substrate
• How can competitive inhibition be reversed?

  By increasing substrate concentration
• Can non-competitive inhibition be reversed by increasing substrate concentration?

  No, it cannot be reversed
• What do non-competitive inhibitors do?

  Bind away from the active site, altering shape
• What is feedback inhibition?

  End product inhibits an earlier enzyme
• When does feedback inhibition occur?

  When end product reaches a critical concentration
• What is the result of feedback inhibition?

  Blocks the pathway, preventing further synthesis