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04/12/2025
Biology
GCSE AQA bioenergetics
54
•
4 Dec 2025
•
GCSE AQA Bioenergetics Revision Notes
G
G
@gurneet
1 / 5
Photosynthetic Reaction and Rate Factors
Photosynthesis is basically how plants make food using sunlight, carbon dioxide, and water to produce glucose and oxygen. Think of it as nature's solar power system that keeps all life on Earth running.
Several factors control how fast photosynthesis happens. Temperature affects how quickly particles move - warmer means faster reactions, but too hot and the enzymes break down. Light intensity determines how much energy the plant has available - more light equals faster photosynthesis until something else runs out.
Carbon dioxide concentration matters because it's one of the raw ingredients plants need. More CO₂ means faster reactions until other factors become limiting. The amount of chlorophyll in leaves also affects the rate since this green pigment captures the light energy.
Quick Tip: Remember that these factors work together - improving just one won't help if the others are limiting the process!
Light Intensity and Commercial Growing
Here's something that might surprise you - light intensity follows the inverse square law, which means doubling the distance from a light source makes it four times dimmer. Triple the distance and it's nine times dimmer. This matters loads for understanding how plants grow at different distances from light sources.
Farmers use this knowledge in greenhouses and polytunnels to maximise crop yields. They can control artificial lighting, temperature, CO₂ levels, and nutrients through hydroponics. However, it's all about balancing costs with profits.
Too much spending on heating and lighting can actually lose money rather than make it. Smart farmers calculate the most cost-effective combination - perhaps keeping temperatures between 20-25°C and boosting CO₂ to 800-1000 parts per million.
Real World: Commercial tomato growers often burn natural gas to produce both heat and CO₂ for their plants - clever economics!
Uses of Glucose and Food Tests
Plants don't just make glucose and leave it sitting around - they're actually quite clever about using it. Glucose gets converted into starch for storage, turned into cellulose to strengthen cell walls, or changed into fats and oils. Plants also combine glucose with nitrate ions from soil to make amino acids for proteins.
You can test for these substances using simple chemical tests. Iodine solution turns blue-black if starch is present, staying orange-brown if there's none. Benedict's solution changes from blue through green, yellow, orange to brick-red when heated with glucose.
Cellular respiration is an exothermic reaction happening constantly in your cells right now. Aerobic respiration uses oxygen and produces loads of energy (about 38 ATP molecules per glucose), whilst anaerobic respiration works without oxygen but only makes 2 ATP molecules.
Memory Trick: Think "AIR-obic" needs oxygen like you need air to breathe, whilst "AN-aerobic" means without air!
Exercise Response and Oxygen Debt
When you exercise, your body goes into overdrive to meet energy demands. Your heart rate and breathing rate increase to pump more oxygenated blood to working muscles. It's like your body's turbo mode kicking in.
If you can't supply enough oxygen, your muscles switch to anaerobic respiration. This produces lactic acid which makes your muscles feel tired and sore. That burning feeling during intense exercise? That's lactic acid building up.
After exercise, you need extra oxygen to clear out the lactic acid - this is called oxygen debt. Your blood carries the lactic acid to your liver where it gets converted back to glucose. This explains why you keep breathing heavily even after you stop exercising.
Sports Science: Elite athletes train to improve their oxygen delivery systems, reducing how quickly they build up oxygen debt during competition!
Metabolism and Molecular Building Blocks
Metabolism is basically the sum of all chemical reactions keeping you alive right now. It includes breaking down molecules for energy and building new ones for growth and repair.
Sugars like glucose get built into complex carbohydrates or broken down for energy. Amino acids link together to form proteins, whilst proteins get broken down into amino acids when needed. Fatty acids and glycerol combine to make lipids (fats and oils) for energy storage.
Your body constantly juggles these processes - converting glucose to glycogen for storage, making proteins from amino acids, and breaking down excess proteins to form urea for excretion. It's like having a incredibly efficient recycling system running 24/7.
Amazing Fact: Your metabolism processes about your entire body weight in ATP (energy currency) every single day - that's some serious molecular recycling!
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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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
GCSE AQA Bioenergetics Revision Notes
G
G
@gurneet
Ever wondered how plants make their own food or why you get out of breath during exercise? Bioenergetics is all about how living things capture, store, and use energy to survive. From photosynthesis in plants to respiration in your muscles,... Show more
Photosynthetic Reaction and Rate Factors
Photosynthesis is basically how plants make food using sunlight, carbon dioxide, and water to produce glucose and oxygen. Think of it as nature's solar power system that keeps all life on Earth running.
Several factors control how fast photosynthesis happens. Temperature affects how quickly particles move - warmer means faster reactions, but too hot and the enzymes break down. Light intensity determines how much energy the plant has available - more light equals faster photosynthesis until something else runs out.
Carbon dioxide concentration matters because it's one of the raw ingredients plants need. More CO₂ means faster reactions until other factors become limiting. The amount of chlorophyll in leaves also affects the rate since this green pigment captures the light energy.
Quick Tip: Remember that these factors work together - improving just one won't help if the others are limiting the process!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
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Light Intensity and Commercial Growing
Here's something that might surprise you - light intensity follows the inverse square law, which means doubling the distance from a light source makes it four times dimmer. Triple the distance and it's nine times dimmer. This matters loads for understanding how plants grow at different distances from light sources.
Farmers use this knowledge in greenhouses and polytunnels to maximise crop yields. They can control artificial lighting, temperature, CO₂ levels, and nutrients through hydroponics. However, it's all about balancing costs with profits.
Too much spending on heating and lighting can actually lose money rather than make it. Smart farmers calculate the most cost-effective combination - perhaps keeping temperatures between 20-25°C and boosting CO₂ to 800-1000 parts per million.
Real World: Commercial tomato growers often burn natural gas to produce both heat and CO₂ for their plants - clever economics!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Uses of Glucose and Food Tests
Plants don't just make glucose and leave it sitting around - they're actually quite clever about using it. Glucose gets converted into starch for storage, turned into cellulose to strengthen cell walls, or changed into fats and oils. Plants also combine glucose with nitrate ions from soil to make amino acids for proteins.
You can test for these substances using simple chemical tests. Iodine solution turns blue-black if starch is present, staying orange-brown if there's none. Benedict's solution changes from blue through green, yellow, orange to brick-red when heated with glucose.
Cellular respiration is an exothermic reaction happening constantly in your cells right now. Aerobic respiration uses oxygen and produces loads of energy (about 38 ATP molecules per glucose), whilst anaerobic respiration works without oxygen but only makes 2 ATP molecules.
Memory Trick: Think "AIR-obic" needs oxygen like you need air to breathe, whilst "AN-aerobic" means without air!
Sign up to see the contentIt's free!
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Improve your grades
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Exercise Response and Oxygen Debt
When you exercise, your body goes into overdrive to meet energy demands. Your heart rate and breathing rate increase to pump more oxygenated blood to working muscles. It's like your body's turbo mode kicking in.
If you can't supply enough oxygen, your muscles switch to anaerobic respiration. This produces lactic acid which makes your muscles feel tired and sore. That burning feeling during intense exercise? That's lactic acid building up.
After exercise, you need extra oxygen to clear out the lactic acid - this is called oxygen debt. Your blood carries the lactic acid to your liver where it gets converted back to glucose. This explains why you keep breathing heavily even after you stop exercising.
Sports Science: Elite athletes train to improve their oxygen delivery systems, reducing how quickly they build up oxygen debt during competition!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Metabolism and Molecular Building Blocks
Metabolism is basically the sum of all chemical reactions keeping you alive right now. It includes breaking down molecules for energy and building new ones for growth and repair.
Sugars like glucose get built into complex carbohydrates or broken down for energy. Amino acids link together to form proteins, whilst proteins get broken down into amino acids when needed. Fatty acids and glycerol combine to make lipids (fats and oils) for energy storage.
Your body constantly juggles these processes - converting glucose to glycogen for storage, making proteins from amino acids, and breaking down excess proteins to form urea for excretion. It's like having a incredibly efficient recycling system running 24/7.
Amazing Fact: Your metabolism processes about your entire body weight in ATP (energy currency) every single day - that's some serious molecular recycling!
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.
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4.9/5
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4.8/5
Google 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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user