How This Topic Appears in Exams

📝 How This Topic Appears in Exams

Typical Question Types

• "Define osmosis / diffusion / active transport" (1-2 marks) — memorise precise definitions. For osmosis: always mention water, partially permeable membrane, and direction (dilute to concentrated).
• "Explain why [cell/structure] is adapted for..." (3-4 marks) — link the structural feature to its transport function. E.g., "The alveoli have a large surface area, which increases the rate of diffusion of oxygen into the blood."
• Required practical questions (RPA2) — you may be asked to describe the method, identify variables, calculate percentage change in mass, or interpret a graph of results against salt concentration.
• Calculation: percentage change in mass — expect at least 1 calculation question. Always show your working and include the % sign and +/− sign in your answer.
• "Explain why active transport requires..." (2-3 marks) — must mention: against the concentration gradient, ATP, mitochondria.
• 6-mark extended response — may ask you to compare all three transport types or explain how the small intestine absorbs food using multiple transport mechanisms.

Key Exam Vocabulary

• Always write "partially permeable membrane" — not just "membrane" or "semi-permeable membrane" (though semi-permeable is accepted).
• For active transport, always include "against the concentration gradient" and "requires energy (ATP)".
• When describing osmosis results, use turgid / flaccid / plasmolysed to pick up technical vocabulary marks.
• For factors affecting diffusion, use "rate" — "the rate of diffusion increases" is better than "diffusion is faster".

Edexcel 1BI0 — Paper 1 (1BI0/1) Notes

On Edexcel Paper 1, cell transport appears in Topic 1: Key Concepts in Biology. Edexcel-specific points to note:

• Scenario-based osmosis questions: Edexcel commonly presents RPA2 (osmosis in plant tissue) in a scenario format — e.g., "A student placed potato cylinders in solutions of different concentrations. The table shows the results." You will be asked to calculate percentage change in mass, plot a graph, and identify the water potential of the potato tissue. Practise all three skills.
• "Suggest" for novel transport contexts: You may be asked to suggest why a particular cell (e.g., a root hair cell, a kidney tubule cell) has many mitochondria. Your answer should link mitochondria → ATP → active transport → against the concentration gradient. Follow the chain of reasoning explicitly.
• Extended writing (6 marks): Edexcel may ask you to compare ALL three transport processes using information from a passage plus your own knowledge. Structure your answer by going through each process in turn, or use a compare-contrast approach — avoid listing random facts.
• Mark scheme flexibility: Edexcel accepts "energy" as well as "ATP" in active transport answers, and "semi-permeable" as well as "partially permeable" for osmosis. Precise terminology always earns marks, but do not worry if you use a valid alternative.