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Britain & the wider world: 1745 -1901
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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
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Biology
6 Dec 2025
494
3 pages
George Mackenzie @eorgeackenzie_qonvnr
Ever wondered how your muscles keep working during an intense workout, or how plants and yeast produce alcohol?... Show more
Think of glycolysis as breaking a six-piece puzzle (glucose) into two three-piece puzzles (pyruvate) - and getting paid in energy for doing it! This happens in your cell's cytoplasm and doesn't need oxygen, making it incredibly versatile.
The process has two main stages phosphorylation and oxidation. During phosphorylation, glucose gets two phosphate groups attached (using 2 ATP), then splits into two triose phosphate molecules. The oxidation stage then converts these into pyruvate, producing 4 ATP and 2 reduced NAD. With a net gain of 2 ATP, you're already ahead!
The link reaction acts like a preparation kitchen for the next stage. Each pyruvate molecule loses a carbon (forming CO₂), gets oxidised, and combines with coenzyme A to form acetyl coenzyme A. This happens twice per glucose molecule and produces 2 reduced NAD molecules.
Quick Tip Remember that everything in the link reaction happens twice because you start with two pyruvate molecules from glycolysis!
The Krebs cycle is like a recycling plant in your mitochondrial matrix that squeezes every bit of energy from acetyl CoA. It's a circular process that regenerates oxaloacetate to keep the cycle spinning.
Starting with acetyl CoA combining with oxaloacetate to form citrate, the cycle involves two decarboxylation steps (removing CO₂) and multiple dehydrogenation reactions. Each turn produces 1 ATP, 3 reduced NAD, and 1 reduced FAD. Since it runs twice per glucose molecule, you get double these amounts.
Oxidative phosphorylation is where the real energy jackpot happens. In the inner mitochondrial membrane, reduced NAD and FAD release hydrogen, which splits into protons and electrons. The electrons travel down the electron transport chain, losing energy that's used to pump protons into the intermembrane space.
This creates an electrochemical gradient that drives chemiosmosis - protons flow back through ATP synthase, producing ATP. Oxygen acts as the final electron acceptor, combining with protons and electrons to form water. The total yield? Up to 32 ATP molecules from one glucose!
Key Point Oxygen is essential here - without it, the electron transport chain stops, and ATP production plummets.
When oxygen runs out, cells don't just give up - they switch to anaerobic respiration! This backup system ensures glycolysis can continue by regenerating NAD from reduced NAD.
In alcoholic fermentation (plants and yeast), pyruvate converts to ethanol and CO₂. This is exactly how bread rises and beer ferments! The process recycles NAD, allowing glycolysis to keep producing ATP even without oxygen.
Lactate fermentation happens in animal cells, including your muscles during intense exercise. Pyruvate converts directly to lactate (lactic acid), which is why your muscles might feel sore after a tough workout. Again, this regenerates NAD to maintain energy production.
While anaerobic respiration produces far less ATP than aerobic respiration, it's a crucial survival mechanism. It keeps essential processes running when oxygen is scarce, though it can only sustain cells for limited periods.
Real-world connection The "burn" you feel during exercise? That's lactate building up in your muscles during anaerobic respiration!
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.
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the key concepts of fermentation in both animals and plants, including glycolysis, ATP production, and the conversion of pyruvate to lactate or ethanol. This summary highlights the differences between aerobic respiration and fermentation, detailing the cellular activities that require ATP and the biochemical pathways involved. Ideal for biology students seeking to understand cellular metabolism.
BiologyExplore the key differences between aerobic and anaerobic respiration, including energy transfer, ATP production, and the role of enzymes. This summary covers the processes involved, equations, and implications for organisms during strenuous exercise. Ideal for students studying cellular energetics and bioenergetics.
BiologyComprehensive summary of respiration processes including glycolysis, Krebs cycle, and oxidative phosphorylation. Ideal for AQA A Level Biology students preparing for exams. Key concepts include ATP production, NADH, and anaerobic respiration pathways.
BiologyExplore the essential processes of aerobic and anaerobic respiration, including key equations, energy release, and the role of lactic acid. This summary covers cellular respiration, fermentation, and their significance in energy production for living organisms. Ideal for students studying cellular bioenergetics.
BiologyExplore the key concepts of anaerobic respiration, including the process of lactic acid fermentation, energy release, and the implications of oxygen debt. This summary covers essential topics such as glycolysis, the differences between aerobic and anaerobic processes, and the role of lactic acid in muscle fatigue. Ideal for GCSE Biology students.
BiologyExplore the processes of aerobic and anaerobic respiration, including energy transfer, metabolic reactions, and the role of enzymes. This summary covers key concepts such as oxygen debt, lactic acid buildup, and fermentation in yeast, providing essential insights for understanding cellular energetics and metabolism. Ideal for biology revision.
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
George Mackenzie
@eorgeackenzie_qonvnr
Ever wondered how your muscles keep working during an intense workout, or how plants and yeast produce alcohol? It all comes down to cellular respiration - the process that extracts energy from glucose to power every cell in your body.... Show more
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Improve your grades
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Think of glycolysis as breaking a six-piece puzzle (glucose) into two three-piece puzzles (pyruvate) - and getting paid in energy for doing it! This happens in your cell's cytoplasm and doesn't need oxygen, making it incredibly versatile.
The process has two main stages: phosphorylation and oxidation. During phosphorylation, glucose gets two phosphate groups attached (using 2 ATP), then splits into two triose phosphate molecules. The oxidation stage then converts these into pyruvate, producing 4 ATP and 2 reduced NAD. With a net gain of 2 ATP, you're already ahead!
The link reaction acts like a preparation kitchen for the next stage. Each pyruvate molecule loses a carbon (forming CO₂), gets oxidised, and combines with coenzyme A to form acetyl coenzyme A. This happens twice per glucose molecule and produces 2 reduced NAD molecules.
Quick Tip: Remember that everything in the link reaction happens twice because you start with two pyruvate molecules from glycolysis!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Krebs cycle is like a recycling plant in your mitochondrial matrix that squeezes every bit of energy from acetyl CoA. It's a circular process that regenerates oxaloacetate to keep the cycle spinning.
Starting with acetyl CoA combining with oxaloacetate to form citrate, the cycle involves two decarboxylation steps (removing CO₂) and multiple dehydrogenation reactions. Each turn produces 1 ATP, 3 reduced NAD, and 1 reduced FAD. Since it runs twice per glucose molecule, you get double these amounts.
Oxidative phosphorylation is where the real energy jackpot happens. In the inner mitochondrial membrane, reduced NAD and FAD release hydrogen, which splits into protons and electrons. The electrons travel down the electron transport chain, losing energy that's used to pump protons into the intermembrane space.
This creates an electrochemical gradient that drives chemiosmosis - protons flow back through ATP synthase, producing ATP. Oxygen acts as the final electron acceptor, combining with protons and electrons to form water. The total yield? Up to 32 ATP molecules from one glucose!
Key Point: Oxygen is essential here - without it, the electron transport chain stops, and ATP production plummets.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When oxygen runs out, cells don't just give up - they switch to anaerobic respiration! This backup system ensures glycolysis can continue by regenerating NAD from reduced NAD.
In alcoholic fermentation (plants and yeast), pyruvate converts to ethanol and CO₂. This is exactly how bread rises and beer ferments! The process recycles NAD, allowing glycolysis to keep producing ATP even without oxygen.
Lactate fermentation happens in animal cells, including your muscles during intense exercise. Pyruvate converts directly to lactate (lactic acid), which is why your muscles might feel sore after a tough workout. Again, this regenerates NAD to maintain energy production.
While anaerobic respiration produces far less ATP than aerobic respiration, it's a crucial survival mechanism. It keeps essential processes running when oxygen is scarce, though it can only sustain cells for limited periods.
Real-world connection: The "burn" you feel during exercise? That's lactate building up in your muscles during anaerobic respiration!
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.
7
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the key concepts of fermentation in both animals and plants, including glycolysis, ATP production, and the conversion of pyruvate to lactate or ethanol. This summary highlights the differences between aerobic respiration and fermentation, detailing the cellular activities that require ATP and the biochemical pathways involved. Ideal for biology students seeking to understand cellular metabolism.
BiologyExplore the key differences between aerobic and anaerobic respiration, including energy transfer, ATP production, and the role of enzymes. This summary covers the processes involved, equations, and implications for organisms during strenuous exercise. Ideal for students studying cellular energetics and bioenergetics.
BiologyComprehensive summary of respiration processes including glycolysis, Krebs cycle, and oxidative phosphorylation. Ideal for AQA A Level Biology students preparing for exams. Key concepts include ATP production, NADH, and anaerobic respiration pathways.
BiologyExplore the essential processes of aerobic and anaerobic respiration, including key equations, energy release, and the role of lactic acid. This summary covers cellular respiration, fermentation, and their significance in energy production for living organisms. Ideal for students studying cellular bioenergetics.
BiologyExplore the key concepts of anaerobic respiration, including the process of lactic acid fermentation, energy release, and the implications of oxygen debt. This summary covers essential topics such as glycolysis, the differences between aerobic and anaerobic processes, and the role of lactic acid in muscle fatigue. Ideal for GCSE Biology students.
BiologyExplore the processes of aerobic and anaerobic respiration, including energy transfer, metabolic reactions, and the role of enzymes. This summary covers key concepts such as oxygen debt, lactic acid buildup, and fermentation in yeast, providing essential insights for understanding cellular energetics and metabolism. Ideal for biology revision.
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