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Cellular transport mechanisms: diffusion, osmosis, and active transport

Cell biology • Transport in cells

Key concepts

What you'll likely be quizzed about

  • Diffusion is the net movement of particles from a higher concentration to a lower concentration.
  • This process occurs when more particles move towards the area of lower concentration than in the opposite direction, resulting in a net flow until equilibrium is reached.
  • Since diffusion is a passive process, it does not require energy, and examples include oxygen moving from alveoli into blood and glucose moving from the small intestine into blood after meals.

Flashcards

Test your knowledge with interactive flashcards

Give an animal example of active transport.

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Cells in the small intestine use active transport to absorb sugars from lower concentrations in the gut into the blood.

Key notes

Important points to keep in mind

Diffusion and osmosis are passive; active transport requires energy (ATP).

Osmosis applies only to water and requires a partially permeable membrane.

Net movement indicates the overall direction after random motions.

Steeper concentration gradients and higher temperatures accelerate diffusion and osmosis.

Surface area to volume ratio and membrane thickness greatly impact exchange rates.

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