Explain why active transport is needed to absorb mineral ions into plant root hair cells from the soil.

AQA GCSE Biology (8461) — 4.1.3 Transport in cells · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

The concentration of mineral ions in the soil water is often lower than the concentration of mineral ions inside root hair cells.

Model answer (4 marks)

Mineral ions are present at a lower concentration in soil water than inside root hair cells, so they must move from a dilute to a concentrated solution.

Diffusion and osmosis can only move substances down a concentration gradient, not against it.

Active transport uses membrane pumps to move ions against the gradient.

These pumps require ATP produced by cellular respiration to function.

Examiner tips

Use the exact phrase ‘move from a dilute to a concentrated solution’ for the first point. Show the direction of diffusion is opposite to the required movement. Mention ‘ATP from respiration’ for the energy source. Keep each point short and to the point to fit the 4‑mark structure.

Common mistakes

Confusing diffusion with osmosis or saying diffusion can move ions against a gradient. Forgetting to mention that active transport requires ATP. Using vague terms like ‘energy’ without specifying respiration or ATP.

Mark scheme (4 marks)

Mineral ions need to move from a more dilute solution (soil water) to a more concentrated solution (inside the root hair cell)
Diffusion / osmosis cannot move substances against a concentration gradient
Active transport moves substances against the concentration gradient
Active transport requires energy from respiration

Key terms in this question

active transport