Fiducia TogetherPhotosynthesis and respiration
How plants make glucose and how all living things release energy from it. Not opposites, and not the same as breathing.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Photosynthesis: carbon dioxide + water → glucose + oxygen, using light energy, in chloroplasts. Aerobic respiration: glucose + oxygen → carbon dioxide + water, releasing energy, in mitochondria. Anaerobic respiration releases less energy and produces lactic acid in animals, or ethanol and carbon dioxide in yeast.
Where it applies
GCSE biology and combined science.
How it works
Photosynthesis is endothermic and respiration exothermic. Plants do both, all the time — a common misconception is that plants respire only at night.
Limiting factors control the rate of photosynthesis: light intensity, carbon dioxide concentration and temperature. Whichever is in shortest supply caps the rate.
How to use it in your work
Learn both word equations exactly, and the symbol equations if you are on the higher tier.
On a limiting factor graph, name which factor is limiting in each region of the curve — that is what the question wants.
Respiration is not breathing. Say "respiration" for the chemical process and "ventilation" or "breathing" for the movement of air.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams. The subject song runs the topics in order.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Biology Song The GCSE biology specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.