Edexcel International A Level Biology

Revision Notes

5.1 Photosynthesis: Overview

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Photosynthesis: Overview

  • Photosynthesis is a series of chemical reactions that occurs in producers such as plants and algae
    • Producers are also known as autotrophs; organisms that make their own organic compounds
  • Photosynthesis converts light energy into chemical energy which is then stored in the biomass of producers
  • The light energy is used to split strong bonds in water molecules (H2O), releasing hydrogen and oxygen
  • Oxygen is released into the atmosphere as a waste product
  • Hydrogen is combined with carbon dioxide to produce glucose 
    • Chemical energy is stored within the bonds in glucose molecules; glucose can therefore function as a fuel for respiration
    • It can be said that hydrogen is stored in glucose molecules


Photosynthesis word equation

Balanced chemical equation for photosynthesis

Photosynthesis requires energy from light to split water molecules. The resulting hydrogen combines with carbon dioxide and is stored in glucose, which fuels respiration. Oxygen is released as a waste product.

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Author: Naomi H

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.