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3.5 Energy transfers in organisms

  • Life depends on continuous transfers of energy.
  • In photosynthesis, light is absorbed by chlorophyll and this is linked to the production of ATP.
  • In respiration, various substances are used as respiratory substrates. The hydrolysis of these respiratory substrates is linked to the production of ATP.
  • In both respiration and photosynthesis, ATP production occurs when protons diffuse down an electrochemical gradient through molecules of the enzyme ATP synthase, embedded in the membranes of cellular organelles.
  • The process of photosynthesis is common in all photoautotrophic organisms and the process of respiration is common in all organisms, providing indirect evidence for evolution.
  • In communities, the biological molecules produced by photosynthesis are consumed by other organisms, including animals, bacteria and fungi. Some of these are used as respiratory substrates by these consumers.
  • Photosynthesis and respiration are not 100% efficient. The transfer of biomass and its stored chemical energy in a community from one organism to a consumer is also not 100% efficient.

Source: AQA Spec

Included in this download

3.5.3Energy and ecosystems
3.5.4Nutrient cycles