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Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
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Biology
29 Nov 2025
187
5 pages
Freya Playford @freyaplayford_mnhy
Ever wondered how plants make their own food and how your body gets energy from that Sunday roast?... Show more
Think of photosynthesis as the ultimate solar panel system that keeps all life on Earth running. Chloroplasts contain a green pigment called chlorophyll that absorbs light energy to power this amazing process.
The basic equation is surprisingly simple carbon dioxide + water → glucose + oxygen. This endothermic reaction needs energy input from sunlight to work, which is why plants can't photosynthesise in the dark.
But what happens to all that glucose? Plants are pretty clever with their sugar - they use it for cellular respiration to release energy, build cellulose to strengthen cell walls, create starch for long-term storage, and even make amino acids by combining glucose with nitrate ions.
Quick Tip Remember that starch is perfect for storage because it's insoluble - unlike glucose, it won't draw water into cells through osmosis and cause them to burst!
Your plant's photosynthesis performance depends on four key factors working together like a well-oiled machine. Light intensity, temperature, carbon dioxide levels, and chlorophyll amount all play crucial roles.
Chlorophyll levels can drop due to disease (like tobacco mosaic virus), environmental stress, or lack of nutrients. When this happens, even perfect conditions won't boost photosynthesis rates.
The graphs show something fascinating - each factor becomes the limiting factor at different points. More light helps until something else (like CO₂) becomes the bottleneck. Temperature works brilliantly until about 45°C when enzymes start denaturing and everything goes wrong.
Reality Check Understanding limiting factors explains why simply blasting plants with more light won't always help - you need the right balance of all conditions!
Smart farmers have figured out how to hack photosynthesis by creating artificial perfect conditions. Greenhouses trap the sun's heat and protect plants from pests, whilst artificial lighting keeps photosynthesis running even during dark winter days.
They pump in extra CO₂ using paraffin heaters (which produce CO₂ as they burn), add fertilisers to provide essential minerals, and use pesticides to eliminate crop-damaging insects.
Cellular respiration is photosynthesis's partner in crime - this exothermic reaction continuously transfers energy from glucose in all living cells. Your body uses this energy for building proteins from amino acids, muscle contraction for movement, and maintaining body temperature.
Cost vs Benefit Farmers must carefully weigh the extra costs of these artificial conditions against the increased crop yield - not every enhancement is worth the expense!
Metabolism encompasses all chemical processes keeping organisms alive, with respiration being the star player. Aerobic respiration is your body's preferred method - it's the most efficient way to extract energy from glucose when oxygen is plentiful.
The equation mirrors photosynthesis in reverse glucose + oxygen → carbon dioxide + water. This process happens in the mitochondria and provides steady energy for daily activities.
Anaerobic respiration kicks in when oxygen runs short, like during intense exercise when your muscles demand more energy than your breathing can supply. It's less efficient but keeps you moving when aerobic respiration can't keep up.
Energy Efficiency Aerobic respiration produces about 32 ATP molecules per glucose, whilst anaerobic only manages 2 - that's why you can't sprint indefinitely!
When you exercise, your muscles work overtime and demand loads of energy through cellular respiration. Your body responds by increasing breathing rate and heart rate to pump oxygen around faster - you can measure these by counting chest movements and checking your pulse.
During intense exercise, anaerobic respiration becomes your backup energy source, but it produces lactic acid as a waste product. This builds up in your tissues, causing that familiar burning sensation in your muscles.
Oxygen debt occurs when you need extra oxygen after exercise to break down the lactic acid that's accumulated. Your blood carries this lactic acid to your liver, where it reacts with oxygen to form glucose again.
Recovery Tip That heavy breathing after a sprint isn't just you being unfit - it's your body working hard to clear lactic acid and restore normal conditions!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
5
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore essential concepts in bioenergetics, including photosynthesis, cellular respiration, and metabolic processes. This study resource covers glucose storage, the impact of light intensity on photosynthesis, and the differences between aerobic and anaerobic respiration. Ideal for GCSE students preparing for higher-tier exams. Enhance your understanding of energy production in living organisms and the factors influencing these processes.
BiologyExplore the essential concepts of bioenergetics, including the processes of photosynthesis and cellular respiration. This summary covers key factors affecting plant growth, the role of chlorophyll, and the significance of fermentation in energy production. Ideal for AQA GCSE Biology (Higher Tier) students preparing for exams.
BiologyExplore the essential processes of photosynthesis and respiration in this comprehensive overview. Understand the key steps, equations, and factors affecting these metabolic pathways. This summary covers light-dependent and light-independent reactions, aerobic and anaerobic respiration, and the role of glucose in energy production. Ideal for students seeking clarity on bioenergetics concepts.
BiologyExplore the impact of temperature and pH on enzyme activity, along with essential food tests for carbohydrates, proteins, and lipids. This summary covers key concepts in biological molecules and enzyme kinetics, ideal for IGCSE Edexcel Biology students aiming for top grades.
Biologycell biology for gcse biology paper 1
BiologyExplore the key processes of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. This summary highlights the conversion of glucose to ATP, the role of NADH and FADH2, and the importance of oxygen in oxidative phosphorylation. Ideal for A Level Biology students.
BiologyApp Store
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
Freya Playford
@freyaplayford_mnhy
Ever wondered how plants make their own food and how your body gets energy from that Sunday roast? Photosynthesis and respiration are like nature's ultimate energy exchange system - plants capture sunlight to make glucose, and then both plants and... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of photosynthesis as the ultimate solar panel system that keeps all life on Earth running. Chloroplasts contain a green pigment called chlorophyll that absorbs light energy to power this amazing process.
The basic equation is surprisingly simple: carbon dioxide + water → glucose + oxygen. This endothermic reaction needs energy input from sunlight to work, which is why plants can't photosynthesise in the dark.
But what happens to all that glucose? Plants are pretty clever with their sugar - they use it for cellular respiration to release energy, build cellulose to strengthen cell walls, create starch for long-term storage, and even make amino acids by combining glucose with nitrate ions.
Quick Tip: Remember that starch is perfect for storage because it's insoluble - unlike glucose, it won't draw water into cells through osmosis and cause them to burst!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your plant's photosynthesis performance depends on four key factors working together like a well-oiled machine. Light intensity, temperature, carbon dioxide levels, and chlorophyll amount all play crucial roles.
Chlorophyll levels can drop due to disease (like tobacco mosaic virus), environmental stress, or lack of nutrients. When this happens, even perfect conditions won't boost photosynthesis rates.
The graphs show something fascinating - each factor becomes the limiting factor at different points. More light helps until something else (like CO₂) becomes the bottleneck. Temperature works brilliantly until about 45°C when enzymes start denaturing and everything goes wrong.
Reality Check: Understanding limiting factors explains why simply blasting plants with more light won't always help - you need the right balance of all conditions!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Smart farmers have figured out how to hack photosynthesis by creating artificial perfect conditions. Greenhouses trap the sun's heat and protect plants from pests, whilst artificial lighting keeps photosynthesis running even during dark winter days.
They pump in extra CO₂ using paraffin heaters (which produce CO₂ as they burn), add fertilisers to provide essential minerals, and use pesticides to eliminate crop-damaging insects.
Cellular respiration is photosynthesis's partner in crime - this exothermic reaction continuously transfers energy from glucose in all living cells. Your body uses this energy for building proteins from amino acids, muscle contraction for movement, and maintaining body temperature.
Cost vs Benefit: Farmers must carefully weigh the extra costs of these artificial conditions against the increased crop yield - not every enhancement is worth the expense!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Metabolism encompasses all chemical processes keeping organisms alive, with respiration being the star player. Aerobic respiration is your body's preferred method - it's the most efficient way to extract energy from glucose when oxygen is plentiful.
The equation mirrors photosynthesis in reverse: glucose + oxygen → carbon dioxide + water. This process happens in the mitochondria and provides steady energy for daily activities.
Anaerobic respiration kicks in when oxygen runs short, like during intense exercise when your muscles demand more energy than your breathing can supply. It's less efficient but keeps you moving when aerobic respiration can't keep up.
Energy Efficiency: Aerobic respiration produces about 32 ATP molecules per glucose, whilst anaerobic only manages 2 - that's why you can't sprint indefinitely!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When you exercise, your muscles work overtime and demand loads of energy through cellular respiration. Your body responds by increasing breathing rate and heart rate to pump oxygen around faster - you can measure these by counting chest movements and checking your pulse.
During intense exercise, anaerobic respiration becomes your backup energy source, but it produces lactic acid as a waste product. This builds up in your tissues, causing that familiar burning sensation in your muscles.
Oxygen debt occurs when you need extra oxygen after exercise to break down the lactic acid that's accumulated. Your blood carries this lactic acid to your liver, where it reacts with oxygen to form glucose again.
Recovery Tip: That heavy breathing after a sprint isn't just you being unfit - it's your body working hard to clear lactic acid and restore normal conditions!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
5
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore essential concepts in bioenergetics, including photosynthesis, cellular respiration, and metabolic processes. This study resource covers glucose storage, the impact of light intensity on photosynthesis, and the differences between aerobic and anaerobic respiration. Ideal for GCSE students preparing for higher-tier exams. Enhance your understanding of energy production in living organisms and the factors influencing these processes.
BiologyExplore the essential concepts of bioenergetics, including the processes of photosynthesis and cellular respiration. This summary covers key factors affecting plant growth, the role of chlorophyll, and the significance of fermentation in energy production. Ideal for AQA GCSE Biology (Higher Tier) students preparing for exams.
BiologyExplore the essential processes of photosynthesis and respiration in this comprehensive overview. Understand the key steps, equations, and factors affecting these metabolic pathways. This summary covers light-dependent and light-independent reactions, aerobic and anaerobic respiration, and the role of glucose in energy production. Ideal for students seeking clarity on bioenergetics concepts.
BiologyExplore the impact of temperature and pH on enzyme activity, along with essential food tests for carbohydrates, proteins, and lipids. This summary covers key concepts in biological molecules and enzyme kinetics, ideal for IGCSE Edexcel Biology students aiming for top grades.
Biologycell biology for gcse biology paper 1
BiologyExplore the key processes of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. This summary highlights the conversion of glucose to ATP, the role of NADH and FADH2, and the importance of oxygen in oxidative phosphorylation. Ideal for A Level Biology students.
BiologyApp Store
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
Sociology