2.3 Energy and ATP

2.3 Energy and ATP

1. Plant cells and animal cells release energy from glucose - respiration

   • However, cells cant get their energy directly from glucose
     • In respiration, the energy released from glucose is used to make ATP (adenosine triphosphate)

2. Structure of ATP

   • Adenine - a nitrogen-containing organic base
   • Ribose - a pentose sugar that acts as a backbone to which other parts are attached
   • Phosphates - a chain of three phosphates
     • It is the bonds between these phosphates where the energy is stored. It is released via hydrolysis reactions

3. How ATP stores energy

   • Bonds between phosphate groups are unstable = they have low activation energy = easily broken
     • When broken these bonds release lots of energy

4. Hydrolysis of ATP

   • ATP + (H2O) --> ADP + Pi + E
     • adenosine triphosphate + water --> adenosine diphosphate + inorganic phosphate + ENERGY
       • Water used to convert ATP to ADP = hydrolysis reaction
         • Reaction catalysed by the enzyme ATP Hydrolase
   • The hydrolysis of ATP can be coupled to energy-requiring cells
     • Energy used directly instead of being lost as heat

5. Synthesis of ATP

   • Catalysed by ATP synthase
   • Reverse of the equation for the hydrolysis of ATP
   • Water removed in process = Condensation reaction
   • Adding an inorganic phosphate to adenosine diphosphate = adenosine triphosphate
     • PHOSPHORYLATION
   • synthesis of ATP from ADP occurs in 3 ways:
     • In chlorophyll-containing plant cells during photosynthesis (photophosphorylation)
     • In plant and animal cells during respiration (oxidative phosphorylation)
     • In plant and animal cells when phosphate groups are transferred from donor molecules to ADP (substrate-level phosphorylation)

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