17.1 Energy Cycles

Question 1

Describe the interrelationship between photosynthesis & respiration:

Answer 1

• reactants for photosynthesis act as products for respiration & vice versa
  
  • photosynthesis forms organic molecules from inorganic molecules - broken down to form inorganic molecules in respiration
  • photosynthesis converts light energy to chemical energy - reversed in respiration
  • photosynthesis stores energy in bonds of organic molecules - respiration releases energy by breaking bonds

Question 2

In respiration, why is the energy required to break bonds of reactants less than the energy released during product formation?

Answer 2

• respiration breaks bonds of organic molecules to form inorganic molecules
  
  • bonds in organic molecules are weaker
    
    • require less energy to break
  • bonds in inorganic molecules are stronger
    
    • release more energy during formation
• excess energy used to synthesise ATP