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Biology AS AQA

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  1. 1-1-biological-molecules-carbohydrates
    11 主题
  2. 1-2-biological-molecules-lipids
    3 主题
  3. 1-3-biological-molecules-proteins
    5 主题
  4. 1-4-proteins-enzymes
    12 主题
  5. 1-5-nucleic-acids-structure-and-dna-replication
    8 主题
  6. 1-6-atp-water-and-inorganic-ions
    4 主题
  7. 2-1-cell-structure
    7 主题
  8. 2-2-the-microscope-in-cell-studies
    4 主题
  9. 2-3-cell-division-in-eukaryotic-and-prokaryotic-cells
    8 主题
  10. 2-4-cell-membranes-and-transport
    9 主题
  11. 2-5-cell-recognition-and-the-immune-system
    7 主题
  12. 2-6-vaccines-disease-and-monoclonal-antibodies
    6 主题
  13. 3-1-adaptations-for-gas-exchange
    6 主题
  14. 3-2-human-gas-exchange
    14 主题
  15. 3-3-digestion-and-absorption
    5 主题
  16. 3-4-mass-transport-in-animals
    6 主题
  17. 3-5-the-circulatory-system-in-animals
    4 主题
  18. 3-6-mass-transport-in-plants
    6 主题
  19. 4-1-dna-genes-and-chromosomes
    10 主题
  20. 4-2-dna-and-protein-synthesis
    3 主题
  21. 4-3-genetic-diversity-mutations-and-meiosis
    7 主题
  22. 4-4-genetic-diversity-and-adaptation
    6 主题
  23. 4-5-species-and-taxonomy
    4 主题
  24. 4-6-biodiversity
    9 主题
课 4, 主题 1
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1-4-1-many-proteins-are-enzymes

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Exam code:7401

Enzymes as proteins

  • Enzymes are globular proteins

  • They act as biological catalysts

    • ‘Biological’ because they function in living systems

    • ‘Catalysts’ because they speed up the rate of chemical reactions without being used up or changed

  • Critical to the enzyme’s function is the active site where the substrate binds

  • Metabolic pathways are controlled by enzymes in a biochemical cascade of reactions

    • Virtually every metabolic reaction within living organisms is catalysed by an enzyme; enzymes are therefore essential for life to exist

  • Enzymes can be intracellular or extracellular, and these determine the structures and functions from the cellular to the whole-organism level

    • Intracellular enzymes are produced and function inside the cell

    • Extracellular enzymes are secreted by cells and catalyse reactions outside cells (e.g. digestive enzymes in the gut)

Examiner Tips and Tricks

Don’t forget that enzymes are proteins, and so anything that could denature a protein, rendering it non-operational (extremes of heat, temperature, pH etc.) would also denature an enzyme.

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