Active Transport
Recap Active Transport for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Unlike diffusion, active transport moves substances against the concentration gradient and needs energy from respiration — think root hairs absorbing mineral ions.
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Topic overview
Active transport moves substances from a more dilute solution to a more concentrated one — against the concentration gradient. Because this is the opposite of the natural direction of diffusion, it requires energy from respiration.
That energy requirement is the defining feature and the reason cells carrying out a lot of active transport contain many mitochondria. Root hair cells are the standard example.
Two examples must be known. Plants absorb mineral ions from very dilute soil solutions into root hair cells, and the human gut absorbs glucose into the blood even when the glucose concentration in the gut is lower than in the blood, ensuring none is lost.
Revision notes
What makes it different
Active transport moves substances against the concentration gradient, from lower to higher concentration.
This requires energy released by respiration, unlike diffusion and osmosis which are passive. Cells doing a lot of active transport have many mitochondria.
Example: mineral ions in plants
Soil solutions are very dilute, so mineral ions are at a lower concentration outside the root than inside.
Active transport moves them into root hair cells against the gradient, allowing the plant to absorb the ions it needs for healthy growth.
Example: glucose in the gut
Glucose is absorbed from the small intestine into the blood.
When the concentration in the gut falls below that in the blood, active transport allows absorption to continue, so no glucose is wasted. This is important for respiration.
Key points
- Active transport moves substances against the concentration gradient.
- It requires energy from respiration.
- Diffusion and osmosis are passive; active transport is not.
- Cells using it have many mitochondria.
- Plants absorb mineral ions from dilute soil solutions.
- The gut absorbs glucose even against the gradient.
Worked examples
Example 1
State one way in which active transport differs from diffusion. [1 mark]
Model answer
Active transport moves substances against the concentration gradient and requires energy, whereas diffusion moves substances down the gradient and requires none (1 mark).
Example 2
Explain why root hair cells contain many mitochondria. [2 marks]
Model answer
Root hair cells absorb mineral ions by active transport, which requires energy (1 mark). Mitochondria release this energy by respiration, so many are needed to supply enough (1 mark).
Example 3
Explain why active transport is needed to absorb glucose in the small intestine. [3 marks]
Model answer
Glucose must be absorbed into the blood so it can be used in respiration (1 mark). Sometimes the glucose concentration in the gut is lower than in the blood (1 mark), so it must be moved against the concentration gradient by active transport, which ensures none is wasted (1 mark).
Common mistakes
Saying active transport is a type of diffusion.
They are opposites in direction and energy requirement.
Forgetting to mention energy.
The energy requirement is the defining feature and almost always carries a mark.
Describing the gradient direction wrongly.
Active transport goes from lower to higher concentration — against the gradient.
Not linking mitochondria to energy.
Say mitochondria release energy by respiration, which active transport requires.
Exam tips
- Always mention both the gradient direction and the energy requirement.
- Learn one plant example and one animal example.
- Link many mitochondria to a high energy demand.
- Contrast it explicitly with diffusion when asked for a difference.
Key terms
- Active transport
- Movement of substances against the concentration gradient using energy.
- Concentration gradient
- The difference in concentration between two regions.
- Mineral ions
- Dissolved nutrients absorbed by plant roots.
- Respiration
- The process releasing energy, used to power active transport.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.