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Flashcards · Biology · Transport in Cells

Diffusion

23 cards

  1. What is diffusion?

    The spreading out of particles of a gas, or of a substance in solution, resulting in a net movement from a higher concentration to a lower concentration.

  2. What does "net movement" mean?

    The overall movement in one direction. Particles move both ways, but more move one way.

  3. Does diffusion need energy from the cell?

    No. The particles move on their own.

  4. What is a concentration gradient?

    The difference in concentration between two places.

  5. Which way do particles move in diffusion?

    From a higher concentration to a lower concentration, down the concentration gradient.

  6. Name two gases that move by diffusion in gas exchange.

    Oxygen and carbon dioxide.

  7. Which waste product diffuses from cells into the blood plasma?

    Urea.

  8. What happens to urea once it is in the blood plasma?

    The kidneys remove it so it can be excreted.

  9. Which way does oxygen diffuse into a respiring cell, and why?

    Into the cell, because oxygen is used up there, so its concentration is lower inside.

  10. Why does carbon dioxide diffuse out of respiring cells?

    Respiration makes it, so its concentration is higher inside the cell.

  11. Name the three factors that affect the rate of diffusion.

    The concentration gradient, the temperature, and the surface area of the membrane.

  12. What happens to the rate of diffusion if the concentration gradient gets bigger?

    It increases.

  13. Why does diffusion speed up as temperature rises?

    The particles have more energy and move faster.

  14. Why does a larger surface area speed up diffusion?

    More particles can cross the membrane at the same time.

  15. When does diffusion stop?

    Never for the particles themselves, but there is no net movement once they are evenly spread.

  16. How do you calculate a rate?

    Divide the amount that changed by the time it took.

  17. A cell takes in 30 units in 6 minutes. What is the rate?

    5 units per minute.

  18. What keeps the concentration gradient steep in the alveoli?

    Breathing brings fresh air in, and flowing blood carries oxygen away.

  19. What is the usual mistake about diffusion?

    Saying particles move only from high to low. They move both ways, but the net movement is from high to low.

  20. Which process moves particles from low to high concentration?

    Active transport, which needs energy.

  21. Particles on both sides of a cell membrane with a marker X on an arrow pointing from the fuller side to the emptier side. What does the arrow marked X show?

    The net movement of particles across the membrane, from the higher concentration to the lower concentration. This is diffusion.

  22. A membrane with many particles on one side and few on the other, with nothing labelled. Label this diagram of diffusion across a cell membrane. The same diagram with higher concentration, lower concentration, the cell membrane and net movement labelled.

  23. Three comparisons: concentration gradient, temperature and surface area, each with a slower and a faster example. Which of these three changes make diffusion faster?

    All three: a bigger concentration gradient, a higher temperature and a larger surface area of membrane.