GCSE biology: cells, respiration and photosynthesis
These pages cover three linked topics from GCSE biology and KS3 science. Cells come first, with diagrams of animal, plant and bacterial cells you can tap. Then come the word equations for respiration and photosynthesis, the magnification formula and the limiting factors of photosynthesis. Each page gives the answer first, then the detail, and says how AQA, Edexcel and OCR word it.
Biology pages
- Photosynthesis equation: carbon dioxide + water → glucose + oxygen
- Respiration equations: aerobic and anaerobic, in words
- Aerobic respiration equation: glucose + oxygen → carbon dioxide + water
- Anaerobic respiration equations: lactic acid, or ethanol and carbon dioxide
- Plant cell diagram: the parts of a plant cell and what they do
- Animal cell diagram: five parts and their jobs
- Bacterial cell diagram: a cell with no nucleus
- Plant and animal cells: what is the same and what is different
- Magnification formula: magnification = image size ÷ real size
- Limiting factors of photosynthesis: light, carbon dioxide and temperature
How the three topics fit together
Every living thing is made of cells. The KS3 curriculum calls the cell the basic unit of living things. Inside it are smaller parts, each with its own job. The nucleus holds the instructions, and the mitochondria carry out respiration. A plant cell also has chloroplasts, where photosynthesis happens.
Those two reactions are the other two topics. Photosynthesis uses light to turn carbon dioxide and water into glucose and oxygen. Respiration breaks glucose down to release the energy a cell needs. The two equations are close to mirror images, so learning one helps with the other.
Magnification links back to cells. Cells are tiny, so you look at them through a microscope. The magnification formula connects the size of the image with the size of the real cell.
Pages on cells
There is one interactive diagram each for the animal cell, the plant cell and the bacterial cell. Tap or tab to a part, and its name and job appear. Turn the labels off when you want to test yourself.
Animal cells have five main parts. Plant cells have those five plus a cell wall, chloroplasts and a permanent vacuole. Bacterial cells are much smaller, have no nucleus and keep their DNA in a single loop. The page on animal and plant cells sets all three side by side in a table of ticks and crosses.
The magnification formula page has a calculator. It works in mm, µm and nm and shows each line of working, with three worked examples.
Pages on respiration and photosynthesis
Start with the respiration equation page if you are not sure which version you need. It sets out all three word equations. The aerobic page adds the symbol equation and an atom count. The anaerobic page covers muscles, yeast and the oxygen debt.
The photosynthesis equation page gives the word and symbol forms and shows what a plant does with the glucose. The page on limiting factors has graphs you can explore, for light, carbon dioxide and temperature.
Where a page shows a symbol equation, a button lists the atoms on each side, so you can see that it balances.
Which boards and levels these pages follow
Every fact here was checked against the current specification from each exam board. That means six GCSE courses:
- AQA GCSE Biology (8461) and Combined Science: Trilogy (8464)
- Edexcel GCSE Biology (1BI0) and Combined Science (1SC0)
- OCR Biology A, Gateway Science (J247)
- OCR Biology B, Twenty First Century Science (J257)
The boards set these topics out in different ways. AQA prints the word equations for respiration and photosynthesis and the magnification formula. Edexcel describes photosynthesis in a sentence and asks you to compare the two kinds of respiration. OCR Gateway asks for the word equations without printing them. Where the boards differ, each page says which board says what.
Some of this is also KS3 work. The KS3 National Curriculum covers the jobs of the main cell parts, how plant and animal cells compare, and word summaries of respiration and photosynthesis. Magnification and limiting factors start at GCSE.
Higher tier content
A few ideas are for Higher tier only, and the pages say so where it applies. The inverse square law for light and the way limiting factors interact are Higher tier on every board. For AQA, the detail of the oxygen debt is Higher tier too. For Edexcel, calculating with standard form is Higher tier.
For teachers
The diagrams and the magnification calculator work on a classroom screen, and nothing needs a login. Our teachers page covers using a game in a lesson and how the site protects your students' privacy.
Common mistakes
- Mixing up breathing and respiration. Breathing moves air in and out of the lungs. Respiration is a chemical reaction in every cell.
- Forgetting that plant cells respire. They have mitochondria and respire day and night, as well as photosynthesising in the light.
- Giving a bacterial cell a nucleus. Its DNA lies free in the cytoplasm.
Each topic has its own game, starting with Cell Builder for the three cell diagrams.
Questions people ask
Is this for GCSE Biology or Combined Science?
Both. For these topics, AQA 8461 and 8464 use the same wording, and so do Edexcel 1BI0 and 1SC0. The one exception here is growing bacteria in the lab, which is in AQA 8461 only.
Do I need to know the balanced symbol equations?
None of the six specifications prints them. AQA lists the formulae of glucose, oxygen, carbon dioxide and water for you to recognise. Ask your teacher which form your course uses.
Are the pages free?
Yes. Every page and game on Crazy Science Games is free, with no sign up.