If you're sitting OCR Twenty First Century Biology B (spec code J257), there are 8 compulsory practicals you need to cover. OCR calls them PAGs (Practical Activity Groups) rather than required practicals, which is just a labelling thing. Each PAG is a group of techniques, and your school picks one specific activity that covers the apparatus and skills listed, or writes its own.
This guide walks through all 8 of them in the order OCR lists them, how they get examined in the Breadth and Depth papers, and the three places OCR B differs from OCR Gateway Biology A if you're trying to work out which spec you're actually on.
Quick language note before we start. OCR says PAGs, AQA says required practicals, Edexcel says core practicals. Same idea, different label. This article is OCR Twenty First Century (OCR B) only. If you're on Gateway A, you want our Gateway Biology practical guide instead.
This article was last checked against the OCR Twenty First Century Biology B (J257) specification on 14 October 2026. OCR revises its specification wording from time to time, so cross-check the official spec PDF before relying on specific detail.
OCR has two Biology specs: Gateway A (J247) and Twenty First Century B (J257). They look similar on paper but they're structured differently and the content is framed differently. Gateway splits content by paper. Twenty First Century uses Breadth and Depth: both papers cover every chapter, differentiated by question style. Check your spec code before you start revising, because the wrong one wastes hours.
All 8 OCR B Biology PAGs
The OCR specification says you need to complete at least eight practical activities, which OCR has split into eight Practical Activity Groups based on Department for Education GCSE subject content requirements. On OCR B separate Biology they're labelled PAG1 to PAG8. On Gateway separate Biology (J247) the same groups are labelled PAG B1 to PAG B8, so the letter prefix isn't a Combined Science thing.
At Higher tier the papers are J257/03 (Breadth) and J257/04 (Depth), each 1 hour 45 minutes, 90 marks, half the qualification each.
| PAG | Title | What it covers |
|---|---|---|
| 1 | Microscopy | Observations of biological specimens; labelled scientific drawings; measurement of length, area, mass, time, temperature, volume and pH |
| 2 | Testing for biological molecules | Qualitative reagents for sugars, starch, protein and lipids; continuous sampling in enzyme investigations |
| 3 | Sampling techniques | Distribution and abundance via field-work; quadrats and belt transects; biotic and abiotic factors |
| 4 | Rates of enzyme-controlled reactions | Bunsen burners or water baths; rate measurement; investigating pH or temperature range |
| 5 | Photosynthesis | Rate of photosynthesis measurement using an aquatic plant such as Cabomba; counting bubbles or measuring gas volume |
| 6 | Physiology, responses, respiration | Effect of exercise on pulse rate, ventilation rate and recovery time |
| 7 | Microbiological techniques | Antimicrobial agents on bacterial lawns; aseptic technique; measuring zones of inhibition |
| 8 | Transport in and out of cells | Osmosis using potato chips in different water potentials; percentage change in mass |
Because each PAG is a group of techniques rather than one prescribed experiment, two schools can teach PAG 4 using completely different enzymes (one school on amylase and starch, another on catalase and hydrogen peroxide) and both count. OCR publishes example activities but centres can swap them for their own. When exam questions reference a PAG they tend to describe the apparatus and ask you to apply the technique, not name a specific experiment, so it doesn't matter which version your class ran.
How practical skills are assessed
There's no separate practical exam. Practical skills get examined through written questions on the Breadth and Depth papers, and your school signs a Practical Science Statement confirming you've actually completed the PAGs. The OCR specification says no less than 15% of the questions will assess practical skills, so a chunky part of your grade sits on this.
In terms of what you're being marked on, AO1 (knowledge and understanding) and AO2 (applying it) each account for 40% of the overall grade. AO3 (analysing, evaluating, improving experimental procedures) is the other 20%. The AO3 bit is where the practical reasoning questions sit, and it's the bit a lot of students underprepare for.
OCR B also runs a whole chapter called B7 "Ideas about Science" on separate J257, which is woven through every paper. B7 isn't a PAG, but it covers scientific method, data interpretation and ethics, and it uses real-world contexts to probe whether you can actually reason about scientific evidence. The lore on OCR B is that the Depth paper extended-response questions nearly always sit at the junction of a PAG and B7, which is more or less how it plays out year on year.
The practical-skills chapter on OCR B separate Biology is Chapter B8, which brings together apparatus and techniques, measurement precision, and analysis of risk.
Ready to boost your grades?
Join 1M+ students who have used Cognito to ace their exams.
Get started for free!
Gateway vs 21st Century
OCR Twenty First Century Biology B differs from OCR Gateway Biology A in three places that matter if you're trying to work out which one you're on.
The first is labelling. OCR B separate Biology has 8 PAGs labelled PAG1 to PAG8. Gateway separate Biology also has 8 PAGs, labelled PAG B1 to PAG B8, and the titles overlap closely: microscopy, biological molecule tests, sampling, enzyme rates, photosynthesis, physiology and respiration, microbiological techniques, and transport in and out of cells both ways. If you see a list of only five labelled PAG B1 to PAG B5, that's a Combined Science list, not a separate Biology list.
The second is paper structure. Gateway Biology splits content between papers so you know Paper 1 covers chapters X to Y and Paper 2 covers the rest. OCR B uses Breadth and Depth: both papers cover all chapters, differentiated only by the style of question. Breadth is multi-topic shorter questions. Depth is deeper application and extended-response synoptic reasoning. Don't go into an OCR B exam expecting "Paper 1 covers topics A to M". Both papers cover everything.
The third is Ideas about Science. OCR B treats scientific method, data interpretation and ethics as an examinable chapter in its own right (Chapter B7 on separate J257), framed around real-world contexts. Gateway handles Working Scientifically differently and doesn't have a direct equivalent of B7 as a standalone examined chapter. A lot of OCR B questions use real contexts like screening programmes, antibiotic resistance, or climate evidence, that would feel out of place on a Gateway paper.
OCR B separate Biology PAGs are PAG1 to PAG8. Gateway J247 uses PAG B1 to PAG B8. A list of only five (B1 Microscopy, B2 Sampling and so on) is a Combined Science list, not a separate Biology list.
Study tips for the 8 PAGs
Reading through the method once isn't really enough. PAGs test whether you can think like a scientist, not whether you can recite the recipe your teacher wrote on the board.
For each PAG, pick the activity your class actually ran and try writing the method out from memory. Then check it against your notes or a Cognito video. The steps you forgot are the ones that would have cost you marks in the exam. Pay attention to the small details OCR likes to probe: incubating microbiology plates at 25 degrees Celsius rather than 37 (to reduce the risk of growing something pathogenic), taping agar lids rather than fully sealing them, blotting potato cylinders before weighing, and measuring the diameter of the clear zone across the disc so you can use pi r squared for its area.
For every PAG, prep answers for the four question types that keep coming up: method, variables, explanation of results, evaluation. The language matters a lot. In an evaluation question, "repeat it" won't score. You want a specific improvement with a specific reason attached.
For the Depth paper, drill linking a PAG back to B7 Ideas about Science. A question on PAG 7 (the antibiotic plates one) can swerve into evaluating whether a particular study was ethical, or how confident you can be in a conclusion given a small sample. The Depth paper rewards you for naming the uncertainty (sample size, confounders, variability) rather than just reporting the result.
The best thing to do is work through past paper questions by PAG. OCR recycles wording and graph shapes year on year, and the mark schemes are the clearest guide to the exact phrases they want to see. Our guide to getting a grade 9 in GCSE Biology walks through exam technique, time management and revision strategies that apply across boards.
The Breadth paper rewards speed and precision across lots of topics. The Depth paper rewards extended reasoning. Match your practice to the paper: Breadth drills with past-paper short-answer sections, Depth drills with 6-mark and extended-response questions that link a PAG to B7.
How Cognito helps
Our OCR Twenty First Century Biology course covers all 8 PAGs through short video lessons, worked examples and exam-style questions. Each PAG has its own lesson walking through the technique, apparatus, variables and exam language, so you can jump straight to the one you're weakest on rather than scrolling through a whole textbook chapter. Dive into the OCR B Biology course to track your progress through the whole spec. For the wider shape of the qualification, our complete guide to OCR Twenty First Century GCSE Biology covers Breadth and Depth paper structure, chapter list and timing in one place.
