GCSE Biology revision (AQA, Edexcel, OCR)

Every living thing is built from cells, and every cell is a bundle of specialised parts. Learn to name the organelles, compare animal, plant and bacterial cells, do magnification maths without unit slips, and follow the cell cycle from DNA copy to two identical daughters.

Cells live or die by what gets across their membranes. Diffusion drifts particles down a gradient, osmosis moves only water, and active transport burns respiration energy to push substances the wrong way. Master the three processes, the potato-chip practical and the surface-area-to-volume maths.

Digestion is applied enzyme chemistry. Learn the lock-and-key model, what heat and wrong pH do to an active site, which enzyme breaks down which food and where, why bile is the gut’s washing-up liquid, and how to run both digestion practicals — plus the rate maths that accompanies them.

A pump, a pipe network and a delivery fluid: the circulatory system in one line. Learn why the heart is a double pump, which vessel carries what and why their walls differ, how each blood cell is shaped for its job, and how stents, statins and transplants fight coronary heart disease.

Health is more than the absence of disease — and diseases gang up. See how immune defects, viruses and stress interact, which lifestyle factors carry proven causal mechanisms, how to tell correlation from cause, and what makes one tumour harmless and another cancer.

A plant is a plumbing project: roots drink, xylem lifts, phloem delivers. Walk through the leaf’s tissue layers, follow the transpiration stream from root hair to stoma, learn what opens and closes the pores, and calculate water-uptake rates like an examiner.

Every infectious disease starts with a pathogen getting past your defences. Meet the viral, bacterial, protist and fungal diseases on the GCSE list, follow the immune response from first contact to immunity, weigh up vaccines and antibiotics, and see how a new drug earns its licence.

This chapter is separate-Biology territory: build antibodies to order with hybridomas, send them hunting for HCG, pathogens or cancer cells, learn how plants spot and fight disease, and grow bacteria safely on agar — with the πr² maths examiners love.

Photosynthesis is the reaction that feeds almost every food chain. Learn the equation, read limiting-factor graphs like an examiner, handle inverse-square light maths, run the pondweed practical, follow glucose through a plant, and weigh up the cost of a warmer, brighter greenhouse.

Respiration is not breathing — it is the exothermic reaction that pays for everything you do. Compare aerobic and anaerobic pathways, follow the body’s exercise responses into oxygen debt, watch yeast ferment your bread, and map the metabolism that respiration powers.

Your body keeps its inside world steady while the outside world swings. See how automatic control systems use negative feedback, trace a reflex arc from finger to spine and back, watch a synapse pass the message, and time your own reflexes with a falling ruler.

Separate-Biology territory: map the three brain regions that run your mind, balance and breathing; follow light through the eye and watch the lens change shape; fix short and long sight; and track how your hypothalamus holds your temperature steady.

Hormones are the body’s slow mail: chemical messages riding the bloodstream. Meet the master gland, watch insulin and glucagon balance your blood sugar, compare the two types of diabetes, and — for separate Biology — follow water through the kidney under ADH’s orders.

The same signalling system that steadies your blood sugar also times fertility and ripens fruit. Follow the four hormones of the menstrual cycle, weigh up contraception and IVF, and — for separate Biology — see how auxin bends a seedling toward the light.

Two ways to make the next generation — shuffle the deck or photocopy it. Compare sexual and asexual reproduction, follow meiosis down to four gametes, unzip the DNA double helix, meet the four bases, and trace a gene’s message from nucleus to ribosome.

Your parents dealt you a hand of alleles and you have been playing it ever since. Learn to read a Punnett square like a bookmaker, work out XX/XY odds, trace polydactyly and cystic fibrosis through family trees, and see how Mendel’s peas started it all.

Life keeps a library of every winning mutation. Follow Darwin’s argument from finches to formal theory, watch resistance evolve in real time in a hospital ward, weigh up selective breeding and GM crops, and file every living thing from domains down to species.

Ecology is accounting with claws: who eats whom, what limits whom, and where every atom goes. Read communities and their limits, follow food chains and the cyclical rise and fall of predators, estimate populations with quadrats, time the decay practical, and close the carbon and water loops.