A scientist is studying the internal structure of a mitochondrion. Explain why the scientist would choose to use an electron microscope rather than a light microscope for this investigation.

Edexcel GCSE Biology (1BI0) — 1.3 Microscopy · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. Electron microscopes use a beam of electrons, which have a much shorter wavelength than visible light, giving them a higher resolving power.
2. The higher resolving power means they can distinguish much smaller details.
3. Mitochondria contain fine internal structures such as cristae that are only a few nanometres wide.
4. A light microscope cannot resolve such small structures, so it would not show the internal structure of a mitochondrion.

Examiner tips

  • Mention electron wavelength vs light wavelength; link to resolution; state that mitochondria are too small for light microscopy; keep answer concise and use exam terminology.

Common mistakes

  • Confusing magnification with resolution; claiming light microscopes have higher magnification; not explaining why higher resolution matters for mitochondria; using vague terms like "more detail" without specifying size.

Mark scheme (4 marks)

  1. Electron microscopes have greater magnification than light microscopes
  2. Electron microscopes have greater resolution / resolving power than light microscopes
  3. This means finer / smaller structures inside the mitochondrion can be seen / distinguished
  4. A light microscope does not have sufficient resolution / magnification to show the internal structure of a mitochondrion

Key terms in this question

electron microscope · light microscope

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