Cell Transport | GCSE Biology

Cell biology

Lesson overview

This lesson introduces the core biology idea, the useful equipment and the calculation or data skills used on this page.

Focusdiffusion, osmosis and active transport

Time45-60 minutes

EquipmentNotebook, calculator and a pen for labelled diagrams.

Practical linkosmosis and concentration-gradient investigations

Maths tagsconcentration gradient, percentage change and surface area

What you will learn

Describe the key biology ideas behind diffusion, osmosis and active transport.
Use precise GCSE command-word language in explanations.
Apply the idea to unfamiliar cells, organisms, data or practical contexts.
Check answers using units, labelled diagrams, observations, calculations or biological evidence where relevant.

Core knowledge

Big idea: Diffusion, osmosis and active transport differ by what moves, which direction it moves, and whether energy is needed.
This lesson focuses on diffusion, osmosis and active transport. A strong answer explains the biology and points to evidence such as cell diagrams, microscope images, concentration gradients and magnification data.
Diffusion: the net movement of particles from a region of higher concentration to lower concentration.
Osmosis: the net movement of water through a partially permeable membrane from a more dilute solution to a more concentrated solution.
Active transport: movement of substances against a concentration gradient using energy from respiration.
Use the model as a thinking route: Particles move down or against a gradient -> Membranes control entry and exit -> Surface area and concentration affect rate.
Likely question evidence: concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data. Use it to justify the explanation, not as decoration.
When numbers or graphs appear, show working with concentration gradient, percentage change and surface area and finish by saying what the result means biologically.

Cell transport and cell division infographic

GCSE Biology infographic showing diffusion, osmosis, active transport and mitosis. — Supplied GCSE Biology visual summary for cell transport and cell division.Download visual

Cell Transport practice set

Use the worked examples and practice questions on this page as a complete study task: learn the definitions of diffusion and osmosis, summarise the infographic in your own words, then answer the questions using the data, equations and observations given here. Check every answer for concentration gradient, percentage change and surface area.

Clear explanation

First secure the anchor idea: diffusion, osmosis and active transport. In ordinary language, this means using diffusion, osmosis and active transport to explain what is happening, not just spotting those words in the question.

Next look for the evidence. In this lesson it is likely to come from concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data.

Then build the answer in order: Particles move down or against a gradient then membranes control entry and exit then surface area and concentration affect rate. This stops the answer becoming a list of disconnected facts.

If the question includes data, use concentration gradient, percentage change and surface area. Keep the unit or comparison visible, then link the result back to diffusion or osmosis.

Exam-ready model sentence: The movement happens because particles or water move in relation to a concentration gradient, with active transport needing energy.

Worked examples

Cell Transport: from idea to explanation

Question: Explain diffusion, osmosis and active transport using the model.

Start with the idea: Particles move down or against a gradient.

Add the mechanism: membranes control entry and exit.

Finish with the consequence: surface area and concentration affect rate.

Reveal worked answer

Answer: A good answer uses diffusion (the net movement of particles from a region of higher concentration to lower concentration), osmosis (the net movement of water through a partially permeable membrane from a more dilute solution to a more concentrated solution) and active transport (movement of substances against a concentration gradient using energy from respiration) in one connected explanation. For example: The movement happens because particles or water move in relation to a concentration gradient, with active transport needing energy.

Cell Transport: from evidence to marks

Question: A student has evidence from concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data. What should their answer include?

Step 1: name the useful evidence rather than writing a general fact about the topic.

Step 2: process any data with concentration gradient, percentage change and surface area.

Step 3: explain what the evidence shows about diffusion and osmosis.

Reveal worked answer

Answer: The answer earns marks by joining evidence, method or data to a biological reason. Avoid naming a cell part or process without explaining how structure, movement or scale affects the result.

Quick checks

Choose an answer, then check your thinking.

1. Which answer would make cell transport clearer?

Particles move down or against a gradient and explain it using diffusion Repeat the topic title without explaining it Ignore the evidence and write a memorised paragraph

2. What should you check before finishing an answer on this lesson?

Whether the answer sounds long enough Whether concentration gradient, percentage change and surface area and evidence such as concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data have been used where needed Whether every keyword from the page has been copied

Practice questions

Question 1

Define diffusion and use it in a complete sentence about diffusion, osmosis and active transport.

Reveal answer and marking guidance

Answer: Diffusion means the net movement of particles from a region of higher concentration to lower concentration. In diffusion, osmosis and active transport, it helps explain particles move down or against a gradient.

Marking: Credit the definition and a sentence that uses the term in the lesson context.

Question 2

Explain the main sequence in Cell Transport using the infographic.

Reveal answer and marking guidance

Answer: Particles move down or against a gradient -> Membranes control entry and exit -> Surface area and concentration affect rate. A strong answer says why the final step follows from the first two steps.

Marking: Credit the correct order plus a biological link between the steps.

Question 3

A question gives evidence such as concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data. What should you do with that evidence?

Reveal answer and marking guidance

Answer: Identify the useful observation, method detail or data first. Then use concentration gradient, percentage change and surface area where relevant and explain what it shows about diffusion, osmosis or active transport.

Marking: Credit evidence use, relevant data handling and a clear biology explanation.

Question 4

A student writes: 'diffusion is involved, so the answer is correct.' What detail is missing?

Reveal answer and marking guidance

Answer: Diffusion means the net movement of particles from a region of higher concentration to lower concentration. A better answer also uses osmosis (the net movement of water through a partially permeable membrane from a more dilute solution to a more concentrated solution) and explains the evidence route: Particles move down or against a gradient then membranes control entry and exit. An exam-ready version could be: The movement happens because particles or water move in relation to a concentration gradient, with active transport needing energy.

Marking: Credit a precise definition, a second linked term and use of evidence or model steps.

Practice ladder

FluencyRecall the key definition, symbol, structure, equation or observation.

ApplicationApply diffusion, osmosis and active transport to unfamiliar organisms, cells, systems, practicals or data.

Practical interpretationUse evidence, method quality, uncertainty or conclusion wording where asked to evaluate.

Maths skillUse units, ratios, graphs and significant figures accurately.

Answers and marking guidance

The exact practice answers are hidden under each question so you can try first. Marks come from using the correct biology model, choosing the right calculation where needed, keeping units with values, labelling diagrams clearly, and explaining changes with precise words such as cells, enzymes, hormones, genes, adaptation, rate, evidence and uncertainty.

Common mistakes

Using diffusion, osmosis or active transport as labels without explaining what they mean.
Forgetting to connect the answer to likely evidence, such as concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data.
Missing the maths or data habit: concentration gradient, percentage change and surface area.
Falling into the common trap of naming a cell part or process without explaining how structure, movement or scale affects the result.

Extension challenge

Create a focused revision card for diffusion, osmosis and active transport: three exact definitions, one model sequence, one evidence detail such as concentration gradients, partially permeable membranes, potato osmosis results, uptake contexts and percentage change data, one data check using concentration gradient, percentage change and surface area, one common misconception, and one exam-ready explanation sentence: The movement happens because particles or water move in relation to a concentration gradient, with active transport needing energy.

Reveal answer

Example answer: A complete response names the biology model, uses accurate units or observations, and explains why the evidence supports the conclusion.