Importance of ATP

• ATP


  Adenosine triphosphate, the universal energy carrier found in all living cells
• Where ATP is produced


  ATP is synthesised in the internal membranes of mitochondria and chloroplasts
• How ATP is synthesised

  1. Involves ATP synthase, an enzyme found embedded in cellular membranes

  2. ATP synthase phosphorylates ADP to form ATP as protons flow through it, down an electrochemical gradient
• Chemiosmosis


  The synthesis of ATP through the movement of protons down their electrochemical gradient across a partially permeable membrane, catalysed by ATP synthase. As the protons move down, energy is released for the attachment of an inorganic phosphate to ADP forming ATP.
• How the proton gradient is maintained during chemiosmosis

  Potential energy associated with excited electrons is coupled to the active transport of H+ across the membrane by proton pumps
• Electron transport chain


  A series of electron carrier proteins each with progressively lower energy levels that transfer electrons in a chain of oxidation-reduction reactions, forming a gradient of protons that enables ATP synthesis
• How dehydrogenase activity in chloroplasts can be investigated


  Using artificial hydrogen acceptors such as DCPIP, methylene blue and tetrazolium compounds
• Colour change when DCPIP is reduced

  Blue to colourless
• Colour change when methylene blue is reduced

  Blue to colourless