AS Bio:Organisms exchange substances- Surface Area to Volume Ratio

  • Created by: Chenda
  • Created on: 22-08-16 13:16

What is it?

Surface area is the outer layer of an cell/object.
Volume is the area inside of a cell/object.

When a object/cell is large the surface area to volume ratio is small. However, when the cell/object is small the surface area to volume ratio is larger meaning the rate of diffusion is more efficient.

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Ficks Law and Rate of Diffusion

Diffusion is the net movement of particles in and out of a cell from a high to a low concentration.

Ficks Law is..

Rate of diffusion = (area of diffusion x difference in concentration ) / (thickness of surface over which diffusion occurs)

Rate of Diffusion is affected by;

  • Surface Area, the greater the surface area the the greater the rate of diffusion.
  • Thickness, of the surface. The thinner the surface the shorter pathway across the surface area meaning greater rate of diffusion.
  • Concentration Gradient, the greater the difference in concentration the greater rate of diffusion.
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