Active transport
Exam-ready definition
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.
How this is marked
The two scoring points students drop: 'against the concentration gradient' and 'energy from respiration' (not just 'energy'). Classic applications in exam questions: root hair cells absorbing ions, and glucose reabsorption in the kidney.
In an exam answer
For root hair cells absorbing minerals: 'Mineral ions are absorbed by active transport, from the lower concentration in the soil to the higher concentration in the cell, against the concentration gradient, using energy from respiration.'
Full topic guide: Movement into & out of cells