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Size and scale of cells to systems

Organisation • Principles of organisation

Key concepts

What you'll likely be quizzed about

  • Cell lengths primarily use micrometres (µm).
  • One micrometre (µm) equals one-thousandth of a millimetre (1 × 10−3 mm) and one-millionth of a metre (1 × 10−6 m).
  • For more precise measurements of sub-cellular structures, nanometre (nm) precision is required, while tissues and organs typically employ millimetres or metres.

Flashcards

Test your knowledge with interactive flashcards

How many micrometres are in one millimetre?

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One millimetre contains 1000 micrometres (1000 µm).

Key notes

Important points to keep in mind

Use consistent units; convert mm, µm, and nm before calculations.

Magnification is unitless; always express measurements for image and actual size correctly.

SA:V decreases as size increases; lower SA:V reduces efficiency of exchanges per unit volume.

Diffusion is efficient only over short distances; larger internal distances necessitate transport systems.

Small cells maintain high SA:V ratios and effective exchanges without needing complex structures.

Specialized exchange surfaces increase area through folding rather than cell size.

Bacterial cells are considerably smaller than typical eukaryotic cells, ranging approximately from 1 to 10 µm.

Electron microscopes provide resolution for viewing nanometre-scale structures; light microscopes suffice for µm-scale cells.

Always display calculations: convert units, measure the image, apply the magnification formula.

Cube experiments illustrate SA:V effects on diffusion efficiency and heat loss.

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