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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 14, 主题 5
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3-2-4-investigating-gas-exchange

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Exam code:7401

Measuring air volume

  • The volumes of air involved in gas exchange can be measured using a respirometer, an experimental set-up that measures oxygen consumption in living organisms

    • Respirometers measure changes in air pressure inside a container

    • As oxygen is consumed the air pressure decreases, causing a drop of coloured liquid to move towards the region of lower pressure

    • The distance moved by the coloured liquid in a given time can be used to calculate the volume of oxygen consumed

  • Respirometers often contain equipment that aids their function, e.g.

    • three-way tap

    • manometer

Three-way taps

  • Three-way taps can be opened to allow air into the respirometer, altering the internal pressure

  • This enables the return of the liquid bead to the starting point to allow easy repeat readings

Diagram of a respirometer setup with seeds, showing a syringe with air, capillary tube, coloured liquid drop, all in a water bath.
Three-way taps allow pressure to be adjusted inside simple respirometers, so enabling the return of coloured liquid to its starting point

Manometers

  • Manometers are narrow tubes that contain liquid, used to determine the difference in air pressure between two sealed containers

  • The liquid in the tube is drawn towards the container where the pressure is lowest, and the distance moved by the fluid can be used to calculate the volume of gas removed

Diagram of a respirometer setup with control and experimental tubes in a water bath. Shows glass beads, germinating seeds, soda lime, and U-tube manometer.
Respirometers can make use of manometers to measure the oxygen consumption of a respiring organism, e.g. germinating seeds

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