Active transport — Cambridge IGCSE Biology
Active transport moves particles against a concentration gradient using energy from respiration and protein carriers.
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Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, against a concentration gradient, using energy from respiration. It uses protein carriers in the membrane. Root hair cells use active transport to absorb mineral ions such as nitrate from the soil, where their concentration is very low.
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Quick check questions
Define active transport.
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The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration.
Where does the energy for active transport come from?
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Respiration.
Supplement Give an example of active transport in plants.
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Ion uptake by root hairs.
Supplement What moves molecules or ions across a membrane in active transport?
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Protein carriers.
Frequently asked questions
Why is active transport important in root hair cells?
Supplement Active transport lets root hair cells absorb mineral ions such as nitrate from the soil, where their concentration is very low, against the concentration gradient. The plant needs these ions for healthy growth. Root hair cells have many mitochondria to release the energy from respiration that active transport needs.
What is the difference between active transport and diffusion?
Active transport moves particles against a concentration gradient, from a lower to a higher concentration, and needs energy from respiration. Diffusion moves particles down a concentration gradient and needs no energy from the cell. This is why active transport stops if respiration stops. Never say that active transport makes energy.
How do protein carriers work in active transport?
Supplement In active transport, a molecule or ion binds to a carrier protein on one side of the cell membrane. The carrier uses energy from respiration and changes shape. The molecule or ion is then released on the other side of the membrane, against its concentration gradient, so cells can take in or remove substances.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026