ATP

• a single molecules of ATP is a nucleotide derivative and is formed from a molecules of ribose, a molecule of adenine and three phosphate groups
• hydrolysis of ATP to ADP and an inorganic phosphate group (Pi) is catalysed by the enzyme ATP hydrolase
• Pi can be used to phosphorylate other compounds, often making them more reactive
• Water is:

  • a metabolite in many metabolic reactions including condensation and hydrolysis reactions
  • an important solvent in which metabolic reactions occur
  • has a relatively high heat capacity, buffering changes in temperature
  • has a relatively large latent heat of vaporization, providing a cooling effect with little loss of water through evaporation
  • has a strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air
• used for:

  • movement
  • active transport
  • synthesis of large molecules
  • secretion of large substances from cells such as releasing hormones from glands
• hydrolysis of ATP releases small amounts of energy so little energy is lost in heat
• ATP broken down in 1 step so energy is released quickly
• rapidly resynthesised so always available
• inorganic phosphate from ATP hydrolysis can phosphorylate other compounds which makes it more reactive
• bonds between phosphate groups are unstable so broken down easily
• soluble so easily transported around cells
• ATP + water --> ADP + Pi (uses enzyme ATP hydrolyase and releases energy)
• ADP + Pi --> ATP + water (uses enzyme ATP synthase + requires energy)