Photosynthesis and respiration are two essential processes that keep life... Show more
Biology167 views·Updated Jun 10, 2026·2 pagesComplete Guide to Bioenergetics - AQA GCSE Biology Topic 4
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oliviaa2008@oliviaa2008
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Photosynthesis: How Plants Make Food
Ever wondered how plants create their own food using just sunlight, water, and carbon dioxide? Photosynthesis is an endothermic reaction that happens in the chloroplasts of plant cells. The green pigment chlorophyll acts like a solar panel, trapping light energy and converting it into chemical energy.
The equation for photosynthesis shows exactly what's happening: carbon dioxide + water → glucose + oxygen . Plants use the glucose they make in brilliant ways - for respiration to release energy, converting it to starch for storage, making cellulose to strengthen cell walls, and producing amino acids for proteins.
Limiting factors control how fast photosynthesis happens. Temperature, light intensity, carbon dioxide concentration, and chlorophyll concentration can all slow things down when they're in short supply. The inverse square law explains why moving a plant twice as far from a light source reduces light intensity by a quarter.
Top Tip: In exam questions about limiting factors, look for which one is preventing the rate from increasing further - that's your limiting factor!
Commercial greenhouses cleverly manipulate these limiting factors to maximise plant growth and profits.
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Cellular Respiration: Releasing Energy for Life
Your cells are constantly working to release energy from food through cellular respiration - an exothermic reaction that happens in the mitochondria. Unlike photosynthesis, this process releases energy and occurs in all living things, not just plants.
Aerobic respiration uses oxygen to completely break down glucose: glucose + oxygen → carbon dioxide + water . When oxygen runs short during intense exercise, your muscles switch to anaerobic respiration, producing lactic acid instead. This causes muscle fatigue and that burning sensation you feel during hard workouts.
Fermentation is anaerobic respiration in yeast and plants, producing ethanol and carbon dioxide . This process is essential for making bread rise and producing alcoholic drinks.
Remember: Aerobic respiration releases much more energy than anaerobic respiration - that's why you can't sprint forever!
Metabolism encompasses all these chemical reactions in your body. The energy from respiration powers everything from building proteins to keeping your body temperature constant, making it absolutely vital for survival.
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Biology167 views·Updated Jun 10, 2026·2 pagesComplete Guide to Bioenergetics - AQA GCSE Biology Topic 4
O
oliviaa2008@oliviaa2008
Photosynthesis and respiration are two essential processes that keep life on Earth running. Photosynthesis lets plants capture sunlight to make food, whilst respiration helps all living things release energy from that food to power their daily activities.
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Photosynthesis: How Plants Make Food
Ever wondered how plants create their own food using just sunlight, water, and carbon dioxide? Photosynthesis is an endothermic reaction that happens in the chloroplasts of plant cells. The green pigment chlorophyll acts like a solar panel, trapping light energy and converting it into chemical energy.
The equation for photosynthesis shows exactly what's happening: carbon dioxide + water → glucose + oxygen . Plants use the glucose they make in brilliant ways - for respiration to release energy, converting it to starch for storage, making cellulose to strengthen cell walls, and producing amino acids for proteins.
Limiting factors control how fast photosynthesis happens. Temperature, light intensity, carbon dioxide concentration, and chlorophyll concentration can all slow things down when they're in short supply. The inverse square law explains why moving a plant twice as far from a light source reduces light intensity by a quarter.
Top Tip: In exam questions about limiting factors, look for which one is preventing the rate from increasing further - that's your limiting factor!
Commercial greenhouses cleverly manipulate these limiting factors to maximise plant growth and profits.
2
of 2Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Cellular Respiration: Releasing Energy for Life
Your cells are constantly working to release energy from food through cellular respiration - an exothermic reaction that happens in the mitochondria. Unlike photosynthesis, this process releases energy and occurs in all living things, not just plants.
Aerobic respiration uses oxygen to completely break down glucose: glucose + oxygen → carbon dioxide + water . When oxygen runs short during intense exercise, your muscles switch to anaerobic respiration, producing lactic acid instead. This causes muscle fatigue and that burning sensation you feel during hard workouts.
Fermentation is anaerobic respiration in yeast and plants, producing ethanol and carbon dioxide . This process is essential for making bread rise and producing alcoholic drinks.
Remember: Aerobic respiration releases much more energy than anaerobic respiration - that's why you can't sprint forever!
Metabolism encompasses all these chemical reactions in your body. The energy from respiration powers everything from building proteins to keeping your body temperature constant, making it absolutely vital for survival.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content: Ribosome
2Most popular content in Biology
9Most popular content
9Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user