OCR A 2.1.5 · 20 written questions · 44 marks · about 55 minutes · marked as you go
This free quiz has 20 written exam questions on biological membranes, all taken from OCR A Level Biology A papers (AS and A level, 2017 to 2025). Short answers and calculations mark themselves. For longer answers you write your answer, then tick off the OCR mark-scheme points you made, so you see exactly where the marks are. The quiz works through OCR A spec 2.1.5, from what membranes do and how they are built to how temperature and solvents change permeability, how substances cross membranes and how water moves by osmosis.
What the quiz covers (OCR A spec 2.1.5)
Roles of membranes (2.1.5(a)): the cell surface membrane and the membranes inside cells
The fluid mosaic model (2.1.5(b)): phospholipids, cholesterol and membrane proteins, and how ions get across
Permeability (2.1.5(c)): temperature, ethanol and freezing, including beetroot practicals
Transport across membranes (2.1.5(d)): simple and facilitated diffusion, active transport, exocytosis and a model cell investigation
Osmosis (2.1.5(e)): defining osmosis, wilting plants, a visking tubing osmometer and plant tissue in sucrose solutions
How to use it
Write every answer in full, as you would in the exam: the mark for each question is shown, so you know how much to write. When you self-mark, only tick a point if your answer clearly makes it, then read the examiner's tip under each question. Your progress is saved on your device, so you can do it in two sittings, and at the end you can retry just the questions where you dropped marks.
Prefer multiple choice? Try the 33-question Biological Membranes multiple choice quiz first.
Open the Biological Membranes quiz in a new tab (easier on a phone)
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Water potential, not water concentration: Students explain osmosis in terms of 'water concentration' or call the membrane 'semi-permeable', neither of which OCR credits at A level.
✔ Gains credit: Osmosis is the net movement of water across a partially permeable membrane down a water potential gradient.
A gradient isn't a place: Many write that water moves 'from a high water potential gradient to a low water potential gradient', which loses the mark.
✔ Gains credit: Water moves from a higher water potential to a lower (more negative) water potential, i.e. down a water potential gradient.
Facilitated diffusion is passive: A very common misconception is that facilitated diffusion uses ATP; and differences are given as one-sided statements such as 'facilitated diffusion uses carrier proteins'.
✔ Gains credit: Both are passive; only facilitated diffusion uses carrier or channel proteins.
Cholesterol depends on temperature: Students assume more cholesterol always means a less fluid membrane, or just describe where cholesterol sits in the bilayer.
✔ Gains credit: Cholesterol increases fluidity at low temperatures and decreases it at high (body) temperatures, so you need to know the temperature.
Heat moves phospholipids apart: When explaining why heat makes membranes more permeable, students write about denatured enzymes instead of the bilayer.
✔ Gains credit: Phospholipids gain kinetic energy, so more or larger gaps form between them and more molecules can cross.
Frozen, then defrosted: Students predict that frozen beetroot leaks less pigment because cold membranes are rigid, missing that it was defrosted.
✔ Gains credit: Water expands as it freezes and ice crystals pierce the membrane, so more pigment leaks out and absorbance is higher.
ATP releases energy: Students write that ATP 'produces' or 'makes' energy, or that exocytosis moves molecules against a concentration gradient.
✔ Gains credit: ATP is hydrolysed to release energy for motor proteins to move the vesicle along the cytoskeleton and for membrane fusion.
A plateau means saturated carriers: Students only consider active transport for an uptake curve that levels off, ignoring facilitated diffusion.
✔ Gains credit: The curve levels off because carrier or channel proteins become saturated, so it could be facilitated diffusion or active transport.
Keep practising
Try the Biological Membranes multiple choice quiz, the Cell Ultrastructure quiz, the Enzymes written quiz or the Cell Cycle, Mitosis and Meiosis written quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.
Questions, mark schemes and examiners' report extracts © OCR.