Photosynthesis — OCR GCSE Biology
Test yourself on Photosynthesis with OCR GCSE practice questions.
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Photosynthesis explained
Photosynthesis is categorized chemically as an endothermic reaction because it absorbs energy from its environmental surroundings.
Read the full explanation
Radiant light energy emitted by the Sun is captured by chlorophyll pigments within chloroplasts and converted into stored chemical energy. The total quantity of energy required to break the chemical bonds in the reactant molecules (carbon dioxide and water) is greater than the energy released during the formation of new bonds in the products (glucose and oxygen). This absorbed energy is locked within the chemical bonds of glucose, establishing the energetic foundation for ecosystems.
Your focus
- Classify photosynthesis as an endothermic chemical reaction.
- Explain how radiant energy is absorbed by chlorophyll during photosynthesis.
- Compare energy changes in photosynthesis with exothermic cellular respiration.
Photosynthesis exam tips
Marking Points
- classifying photosynthesis as an endothermic reaction
- explaining that photosynthesis absorbs light energy from the surroundings via chlorophyll
- stating that energy required to break bonds in CO₂ and H₂O exceeds energy released forming products
Examiner Tips
- 💡Clearly state that photosynthesis takes in light energy, making it an endothermic process.
- 💡Link endothermic reactions to chemical energy storage in the chemical bonds of the synthesized glucose.
Common Mistakes
- confusing endothermic (absorbs energy, photosynthesis) with exothermic (releases energy, respiration)
- stating that photosynthesis produces heat or warms the surroundings, misunderstanding energy absorption