ATP

• What are the components of ATP?


  Adenine, ribose and three phosphates
• What does ATP stand for?


  Adenosine triphosphate
• How is ATP synthesised?


  • Condensation reaction between ADP and Pi
  • Component molecules: adenine, ribose and three phosphates
  • Catalysed by ATP synthase
  • ADP + Pi —-> ATP + water
• When is ATP synthesised?


  During respiration (oxidative phosphorylation) and photosynthesis (photophosphorylation)
• How is ATP broken down?


  • Hydrolysis reaction
  • Catalysed by ATP hydrolase
  • Releases energy
  • ATP + water ——> ADP + Pi
• What is the function of the hydrolysis of ATP?


  • Releases energy instantaneously
  • Releases phosphate that can be added to other substances and make them more reactive
• Why ATP?


  • Releases a relatively small amount of energy so is more manageable than glucose
  • Releases energy instantaneously
  • Can phosphorylate other substances, making them more reactive
  • Can be rapidly re-synthesised
  • Does not leave cells
• Why can ATP be hydrolysed readily?


  Unstable bonds between the phosphates that have a low activation energy and can be broken easily.
• Because ATP is a good immediate energy source, it is also…


  A poor long-term energy store
• What is ATP used in?


  • Metabolic processes
  • Movement
  • Active transport
  • Secretion
  • Activation of molecules
• 1. Metabolic Processes


  Provides the energy to build up macromolecules from their basic units.
• 2. Movement 


  Provides the energy for muscle contraction (for the filaments to slide past one another and therefore shorten the overall length of a muscle fibre).
• 3. Active Transport 


  Provides the energy to change the shape of carrier proteins in plasma membranes, allowing molecules or ions to be moved against the concentration gradient.
• 4. Secretion 


  Needed to form lysosomes, which are necessary for the secretion of cell products.
• 5. Activation of Molecules 


  The inorganic phosphate released can be used to phosphorylate other compounds in order to make them more reactive, thus lowering he activation energy in enzyme-catalysed reactions. e.g. the addition of phosphate to glucose at the start of glycosis.