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Flashcards · Biology · Transport In and Out of Cells

Surface Area to Volume Ratio and Exchange Surfaces

20 cards

  1. What is surface area to volume ratio?

    The surface area of an object divided by its volume.

  2. What happens to the surface area to volume ratio as an object gets bigger?

    It gets smaller.

  3. A cube has sides of 2 cm. What is its surface area?

    6 × (2 × 2) = 24 cm².

  4. A cube has sides of 2 cm. What is its volume?

    2 × 2 × 2 = 8 cm³.

  5. What is the surface area to volume ratio of a 2 cm cube?

    24 ÷ 8 = 3, so 3:1.

  6. Why can a single-celled organism manage without a transport system?

    It has a large surface area to volume ratio, so diffusion across its surface meets all its needs.

  7. Why can't diffusion alone supply the cells of a large animal?

    The surface area to volume ratio is small and the distances are long, so diffusion is far too slow.

  8. Why do multicellular organisms need exchange surfaces?

    Their body surface is too small for their volume, so they need specialised surfaces to swap materials quickly.

  9. Name the four features of an effective exchange surface.

    Large surface area, thin membrane, efficient blood supply (in animals) and ventilation (in animals, for gas exchange).

  10. Why does a thin membrane help exchange?

    It gives a short diffusion path.

  11. Why does a blood supply help exchange?

    It carries substances away, keeping the concentration gradient steep.

  12. What are villi, and what do they do?

    Finger-like folds in the small intestine wall that give a large surface area for absorbing digested food.

  13. What is an alveolus?

    A tiny air sac in the lungs where oxygen and carbon dioxide are exchanged.

  14. How are the lungs ventilated?

    By breathing, which moves fresh air in and stale air out.

  15. How is a fish's gill adapted for gas exchange?

    Many thin gill filaments give a large surface area, with a rich blood supply and water flowing over them.

  16. How does a root hair cell help a plant?

    Its long thin extension gives a large surface area for taking up water and mineral ions.

  17. How are leaves adapted for gas exchange?

    They are flat and thin, with air spaces inside giving a large surface area, and stomata to let gases in and out.

  18. Three cubes with sides 1 cm, 2 cm and 3 cm and an empty table under each. Work out the surface area to volume ratio of each cube. The three cubes with their surface areas, volumes and ratios filled in.

    Surface areas 6, 24 and 54 cm². Volumes 1, 8 and 27 cm³. Ratios 6:1, 3:1 and 2:1. The ratio falls as the cube gets bigger.

  19. An alveolus beside a capillary with a pointer marked X to the capillary. Name the structure marked X in this lung and say how it helps gas exchange.

    A capillary. It carries a rich blood supply that takes oxygen away and brings carbon dioxide, keeping the concentration gradient steep.

  20. An alveolus beside a capillary with unlabelled arrows. Label every part of this gas exchange surface. The same alveolus and capillary with every part labelled.

    Alveolus, thin wall one cell thick, capillary, red blood cells, oxygen in, carbon dioxide out, air in and air out.