Cell Membrane & Transport
The cell membrane is a partially permeable barrier that controls the movement of substances into and out of the cell. The fluid mosaic model describes the membrane as a phospholipid bilayer with embedded proteins, cholesterol, glycoproteins, and glycolipids. Transport across the membrane can be passive (diffusion, facilitated diffusion, osmosis) or active (requiring energy).
Full topic guide: the detailed syllabus page with worked examples and common mistakes lives at studyvector.co.uk/a-level/biology/cells/cell-membrane-transport.
Topic preview: Cell Membrane & Transport
Sample stems from the StudyVector question bank (AQA · Edexcel · OCR) — not generic filler text.
More questions are being linked to this topic. You can still start low-focus cards after you create a free account.
Coverage and provenance
What this page is based on
StudyVector does not present unsupported question coverage as complete. Read how questions are selected and reviewed.
Topic explanation
The cell membrane is a partially permeable barrier that controls the movement of substances into and out of the cell. The fluid mosaic model describes the membrane as a phospholipid bilayer with embedded proteins, cholesterol, glycoproteins, and glycolipids. Transport across the membrane can be passive (diffusion, facilitated diffusion, osmosis) or active (requiring energy).
Cell Membrane & Transport is easiest to revise when it is treated as a precise exam behaviour, not a loose note-taking category. In A-Level Biology, the goal is to recognise how the topic appears in a question, identify the command word, and decide what evidence, method, or vocabulary earns marks. StudyVector keeps this page tied to AQA · Edexcel · OCR language where coverage is available, then routes practice towards the same topic so revision moves from explanation into retrieval.
A strong revision session starts with a short recall check. Write down the rule, definition, process, or method linked to Cell Membrane & Transport before looking at any notes. Then answer one exam-style prompt and compare your answer with the mark-scheme logic: did you make a clear point, support it with the right step, and avoid drifting into a nearby topic? This matters because many lost marks come from almost-correct answers that do not match the expected structure.
Use this guide as the first layer: understand the topic, look at the worked examples, complete the mini quiz, then move into full practice. The full StudyVector practice loop is designed to capture whether mistakes are caused by knowledge, method, language, or timing. That distinction is important. If the error is factual, you need reteaching. If the error is method-based, you need a worked retry. If the error is wording, you need command-word calibration. That is how Cell Membrane & Transport becomes a controlled revision target rather than another page in a folder.
Lost marks → repair task
Why marks are usually lost here
These are the error patterns StudyVector looks for after an attempt. The goal is not a generic explanation; it is one repair move and one follow-up question.
Command-word miss
Examiner move: Answer the action in the command word before adding extra detail.
Repair drill: 60-second rewrite: start the answer with explain, compare, evaluate, state, or calculate in mind.
Weak evidence or data reference
Examiner move: Use a precise value, quote, example, diagram feature, or syllabus term to support the claim.
Repair drill: Add one concrete reference to the answer and remove any generic sentence that does not earn a mark.
Missing chain of reasoning
Examiner move: Show the link between point, method, evidence, and conclusion instead of jumping to the final line.
Repair drill: Write the missing because/therefore step, then retry one isomorphic question.
Mini quiz
Use these checks before full practice. They test topic recognition, exam technique, and whether you can connect the explanation to a marked response.
1. What should you check first when a Cell Membrane & Transport question appears in A-Level Biology?
- A.The command word and the exact topic focus
- B.The longest paragraph in your notes
- C.A memorised answer from a different topic
2. Which revision action gives the strongest evidence that Cell Membrane & Transport is improving?
- A.Rereading the explanation twice
- B.Answering a timed exam-style question and reviewing lost marks
- C.Highlighting every key phrase in the topic notes
Sample questions
Topic-specific public question previews are still being reviewed. We keep them off public pages until the topic match is safe.
Exam tips
- Read the command word carefully — "explain" needs reasons; "state" expects a short fact.
- For Cell Membrane & Transport, show structured working even when you are practising multiple choice — it builds accuracy under time pressure.
- Mark yourself against the mark scheme style: one clear point per mark, in logical order.
- Come back to this topic after a day or two; short spaced reviews beat one long cram.
Worked examples
Example 1
Modelled exam response
To calculate water potential, you can use the formula: Ψ = Ψs + Ψp. If a plant cell has a solute potential (Ψs) of -0.7 MPa and a pressure potential (Ψp) of 0.5 MPa, its water potential (Ψ) is -0.7 + 0.5 = -0.2 MPa. Water will move from a region of higher water potential to a region of lower water potential.
Example 2
Identify the task before answering
Question type: a Cell Membrane & Transport prompt asks for a clear response in A-Level Biology. Step 1: underline the command word. Step 2: name the exact part of Cell Membrane & Transport being tested. Step 3: decide whether the mark scheme wants a definition, method, explanation, comparison, or calculation. Why it works: most weak answers fail before the content starts because they answer the topic generally rather than the exact exam task.
Example 3
Turn feedback into a repair task
Suppose your answer shows partial understanding but loses marks for precision. First, rewrite the missing mark as a short target: "I need to state the mechanism, unit, reason, or evidence explicitly." Then answer one similar question without notes. Finally, compare the second attempt with the first and check whether the same mark was recovered. Why it works: Cell Membrane & Transport improves faster when feedback creates a specific retry, not another passive reading session.
Next revision routes from this subject
Good topic pages should lead naturally into the next useful page. Use these links to stay inside the same strand or jump into the next topic area without starting your search again.
Stay in the same topic area
Common mistakes
- Confusing simple diffusion with facilitated diffusion. Simple diffusion is the movement of small, nonpolar molecules directly through the phospholipid bilayer, while facilitated diffusion requires a channel or carrier protein for polar molecules and ions.
- Not understanding the role of cholesterol. Cholesterol molecules are interspersed within the phospholipid bilayer, regulating the fluidity of the membrane. At high temperatures, it reduces fluidity, and at low temperatures, it prevents the membrane from becoming too rigid.
- Forgetting that active transport requires ATP. Active transport moves substances against their concentration gradient, from a region of lower concentration to a region of higher concentration, and this process requires energy from the hydrolysis of ATP.
Exam board notes
The fluid mosaic model of the cell membrane and the different mechanisms of transport are fundamental concepts covered by all A-Level Biology boards (AQA, Edexcel, OCR). The specific examples and experimental techniques, such as investigating the effect of temperature on membrane permeability, may differ.
FAQs
What is osmosis?
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential.
How does active transport work?
Active transport uses carrier proteins that bind to specific molecules or ions. ATP provides the energy to change the shape of the protein, moving the substance across the membrane against its concentration gradient.
More on StudyVector
Full practice set
The complete adaptive question bank for this topic — personalised to your weak areas — is available after you sign in. Your session can start on this topic immediately.