ATP

• ATP


  Universal energy currency
• ATP


  • Provides energy in all cells for all reactions
  • Releases energy in small, usable amounts
  • Easily hydrolysed, removing the terminal phosphate group to release energy, forming ADP
• Phosphorylation


  1. ADP converted to ATP by ATP synthetase

  2. ATP synthetase spans a membrane

  3. Potential energy to drive enzyme comes from flow of protons down electrochemical gradient

  4. This is chemiosmosis
• Chemiosmosis


  Process where protons flow down electrochemical gradient to drive ATP synthesis
• Creating an electrochemical gradient - the electron transport chain

  1. Hydrogen atoms delivered to chain

  2. High energy electrons power proton pump to pump H+ ions through membrane

  3. Electron carrier molecules shuttle electrons to next proton pump

  4. Results in build up of protons on one side of membrane that can diffuse back through ATP synthetase
• Mitochondria - oxidative phosphorylation

  • Proton pumps on inner mitochondrial membrane powered by high energy electrons from hydrogen
  • Pump protons into intermembrane space forming electrochemical gradient
  • Protons flow from intermembrane space through ATP synthetase back into matrix, combining with electrons and oxygen to form water
• Chloroplast - Photophosphorylation


  1. Electrons excited by photons of light passed along electron transport chain, powering proton pumps to pump protons into thylakoid space

  2. Protons flow from thylakoid space through ATP synthetase back into stroma, phosphorylating ADP to ATP

  3. Protons combine with electrons and NADP to form NADPH for Calvin cycle