GCSE Biology (AQA)

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Single-Celled Organisms

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Cell Biology Transport in Cells

Single-Celled Organisms

1:48 Diffusion in Action
Spec 4.1.3.1
Previous Surface Area to Volume Ratio Next Multicellular Organisms
  • Single-celled organisms have a large surface area to volume ratio.
  • A diagram illustrates a single-celled organism with a 6:1 surface area to volume ratio.
  • Multicellular organisms have lower surface area to volume ratios, examples given are 3:1 and 2:1.
  • As organisms increase in cell number (from single-celled to multicellular), the surface area to volume ratio decreases.
  • A higher surface area to volume ratio facilitates a faster rate of diffusion.
  • The rate of diffusion decreases as the surface area to volume ratio decreases from single-celled to multicellular organisms.
  • For exams, it's important to know that single-celled organisms have a relatively large surface area to volume ratio.
  • The large surface area to volume ratio in single-celled organisms is crucial for efficient diffusion.
  • Single-celled organisms rely on diffusion for the intake of oxygen and the expulsion of carbon dioxide.
  • The large surface area to volume ratio allows for adequate transport of molecules to meet the cell's metabolic needs.
  • Fast diffusion is necessary to sustain the metabolic demands of the cell and to eliminate waste products.

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