Doc Brown's GCSE OCR 21st Century Science-Biology Revision Notes

OCR GCSE 21st Century Additional Science Biology Module B4 The processes of life

Unit B4.1 How do chemical reactions take place in living things?

  • 1. understand that the basic processes of life carried out by all living things depend on chemical reactions within cells that require energy released by respiration

  • 2. understand the role of photosynthesis in making food molecules and energy available to living organisms through food chains.

  • 3. be able to describe photosynthesis as a series of chemical reactions that use energy from sunlight to build large food molecules in plant cells and some microorganisms (eg phytoplankton)

  • 4. be able to describe respiration as a series of chemical reactions that release energy by breaking down large food molecules in all living cells

  • 5. know that enzymes are proteins that speed up chemical reactions

  • 6. know that cells make enzymes according to the instructions carried in genes

  • 7. understand that molecules have to be the correct shape to fit into the active site of the enzyme (the lock and key model)

  • 8. understand that enzymes need a specific constant temperature to work at their optimum, and that they permanently stop working (denature) if the temperature is too high

  • 9. HT only: be able to explain that enzyme activity at different temperatures is a balance between:

    • a) increased rates of reaction as temperature increases

    • b) changes to the active site at higher temperatures, including denaturing

      • You are not expected to explain why rates of reaction increase with temperature here

  • 10. know that an enzyme works at its optimum at a specific pH

  • 11. HT only: be able to explain the effect of pH on enzyme activity in terms of changes to the shape of the active site.

  • Revision Notes