Active Transport: Against the Gradient Using Energy
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
Active transport moves particles through a cell membrane from lower to higher concentration, against the concentration gradient, using energy from respiration. Extended students also need root-hair and carrier-protein applications.
Active transport is the only one of the three membrane-transport processes that moves particles against a concentration gradient and requires energy from respiration. Most lost marks come from naming only one of those two features.
The definition that earns the marks
Describe active transport as the movement of particles through a cell membrane from a region of lower concentration to higher concentration, against the concentration gradient, using energy from respiration.
“Uses energy” is incomplete when the question expects the biological source. “Moves substances into the cell” is also incomplete because diffusion can do that too.
Why root hair cells need active transport
Mineral ions may be at a lower concentration in the soil than inside the root-hair cell. Diffusion cannot move them from lower to higher concentration. Carrier proteins in the membrane move the ions against the gradient using energy released by respiration.
Root hair cells have a long extension for a large surface area and many mitochondria to support energy-demanding uptake. Link each feature to its function rather than listing adaptations without reasons.
Diffusion, osmosis and active transport compared
Process
What moves
Direction
Respiration energy?
Diffusion
Particles
Higher to lower concentration
No
Osmosis
Water molecules
Higher to lower water potential
No
Active transport
Molecules or ions
Lower to higher concentration
Yes
Try a focused question (3 marks)
The concentration of nitrate ions is lower in the soil than inside a root hair cell. Explain how the cell still absorbs nitrate ions.
Show the answer and marking guidance
Nitrate ions move by active transport.
They move from lower concentration in the soil to higher concentration in the cell, against the gradient.
The process uses energy from respiration, with membrane carrier proteins credited at Supplement level.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Describing movement down the gradient.
Naming osmosis for mineral ions.
Saying energy is produced rather than released by respiration.
Mentioning carrier proteins but not the concentration direction.