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29 Mar 2023
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OCR A-Level Biology Respiration Notes - Glycolysis, Krebs Cycle, and Anaerobic Respiration
Niamh Cooke
@niamhcooke_yelp
Oxidative Phosphorylation and Respiratory Substrates
This page delves into the final stage of aerobic respiration - oxidative phosphorylation - and discusses various respiratory substrates and their energy yields.
Oxidative Phosphorylation
Oxidative phosphorylation is the process by which the majority of ATP is synthesized in the electron transport chain within the mitochondria.
Definition: Oxidative phosphorylation is the production of ATP using the energy from the electron transport chain and the resulting proton gradient.
Key aspects of oxidative phosphorylation: • Occurs in the inner mitochondrial membrane • Utilizes reduced coenzymes from earlier stages • Involves a series of redox reactions in the electron transport chain • Creates a proton gradient across the inner mitochondrial membrane • ATP is produced as protons flow back through ATP synthase
Highlight: Oxygen acts as the final electron acceptor in the electron transport chain, combining with protons to form water.
ATP Yield and Efficiency
The theoretical yield of ATP per glucose molecule is 38, but this is rarely achieved due to factors such as: • "Leaky" inner mitochondrial membrane • ATP required for active transport of pyruvate
Respiratory Substrates
Respiratory substrates include carbohydrates, lipids, and proteins, each releasing varying amounts of energy depending on their hydrogen content.
Vocabulary: Respiratory Quotient - the ratio of CO₂ produced to O₂ consumed during respiration, used to determine which respiratory substrate is being used.
RQ values for different substrates: • Carbohydrates: RQ = 1 • Lipids: RQ = 0.8 • Proteins: RQ = 0.9
Example: A measured RQ of 0.8 would indicate that lipids are the primary respiratory substrate being used.
This comprehensive guide covers all major aspects of OCR A Level Biology respiration, including detailed explanations of glycolysis, the link reaction, Krebs cycle, and oxidative phosphorylation. It provides essential information for understanding both aerobic and anaerobic respiration processes, making it an invaluable resource for exam preparation and in-depth study of cellular energy production.
Aerobic Respiration Overview
Aerobic respiration is a multistep process that releases energy from respiratory substrates using oxygen. This page covers the initial stages of respiration, including glycolysis and the link reaction.
Glycolysis
Glycolysis is the first process in both aerobic and anaerobic respiration, occurring in the cytoplasm.
Definition: Glycolysis is the splitting of glucose into two pyruvate molecules, producing a net gain of 2 ATP and 2 NADH.
The process involves phosphorylation of glucose and results in: • 2 pyruvate molecules • 2 NADH molecules • Net production of 2 ATP molecules
The Link Reaction
Following glycolysis, the link reaction converts pyruvate to acetyl-CoA.
Highlight: The link reaction connects glycolysis to the Krebs cycle by producing acetyl-CoA, which enters the cycle.
Key points of the link reaction: • Occurs when oxygen is present • Converts pyruvate to acetyl, which binds to Coenzyme A • Produces NADH and CO₂
Anaerobic Respiration
When oxygen concentration is low, cells can still produce some ATP through anaerobic respiration.
Example: In mammals, pyruvate is converted to lactate during anaerobic conditions, allowing glycolysis to continue.
Anaerobic respiration in different organisms: • Mammals: Pyruvate → Lactate • Yeast and plants: Alcoholic fermentation
The Krebs Cycle
The Krebs cycle, also known as the citric acid cycle, is a series of reactions that complete the oxidation of glucose.
Vocabulary: Substrate-level phosphorylation - the production of ATP by direct transfer of a phosphate group from a substrate to ADP.
Key points of the Krebs cycle: • Occurs twice for each glucose molecule • Produces 4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP per glucose • ATP is produced via substrate-level phosphorylation
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Stefan S
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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
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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
OCR A-Level Biology Respiration Notes - Glycolysis, Krebs Cycle, and Anaerobic Respiration
Niamh Cooke
@niamhcooke_yelp
OCR A Level Biology Respiration: A comprehensive guide to aerobic and anaerobic respiration processes, including glycolysis, the link reaction, Krebs cycle, and oxidative phosphorylation. This summary covers key concepts, equations, and cellular locations for each stage of respiration, providing... Show more
Oxidative Phosphorylation and Respiratory Substrates
This page delves into the final stage of aerobic respiration - oxidative phosphorylation - and discusses various respiratory substrates and their energy yields.
Oxidative Phosphorylation
Oxidative phosphorylation is the process by which the majority of ATP is synthesized in the electron transport chain within the mitochondria.
Definition: Oxidative phosphorylation is the production of ATP using the energy from the electron transport chain and the resulting proton gradient.
Key aspects of oxidative phosphorylation: • Occurs in the inner mitochondrial membrane • Utilizes reduced coenzymes from earlier stages • Involves a series of redox reactions in the electron transport chain • Creates a proton gradient across the inner mitochondrial membrane • ATP is produced as protons flow back through ATP synthase
Highlight: Oxygen acts as the final electron acceptor in the electron transport chain, combining with protons to form water.
ATP Yield and Efficiency
The theoretical yield of ATP per glucose molecule is 38, but this is rarely achieved due to factors such as: • "Leaky" inner mitochondrial membrane • ATP required for active transport of pyruvate
Respiratory Substrates
Respiratory substrates include carbohydrates, lipids, and proteins, each releasing varying amounts of energy depending on their hydrogen content.
Vocabulary: Respiratory Quotient - the ratio of CO₂ produced to O₂ consumed during respiration, used to determine which respiratory substrate is being used.
RQ values for different substrates: • Carbohydrates: RQ = 1 • Lipids: RQ = 0.8 • Proteins: RQ = 0.9
Example: A measured RQ of 0.8 would indicate that lipids are the primary respiratory substrate being used.
This comprehensive guide covers all major aspects of OCR A Level Biology respiration, including detailed explanations of glycolysis, the link reaction, Krebs cycle, and oxidative phosphorylation. It provides essential information for understanding both aerobic and anaerobic respiration processes, making it an invaluable resource for exam preparation and in-depth study of cellular energy production.
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
Aerobic Respiration Overview
Aerobic respiration is a multistep process that releases energy from respiratory substrates using oxygen. This page covers the initial stages of respiration, including glycolysis and the link reaction.
Glycolysis
Glycolysis is the first process in both aerobic and anaerobic respiration, occurring in the cytoplasm.
Definition: Glycolysis is the splitting of glucose into two pyruvate molecules, producing a net gain of 2 ATP and 2 NADH.
The process involves phosphorylation of glucose and results in: • 2 pyruvate molecules • 2 NADH molecules • Net production of 2 ATP molecules
The Link Reaction
Following glycolysis, the link reaction converts pyruvate to acetyl-CoA.
Highlight: The link reaction connects glycolysis to the Krebs cycle by producing acetyl-CoA, which enters the cycle.
Key points of the link reaction: • Occurs when oxygen is present • Converts pyruvate to acetyl, which binds to Coenzyme A • Produces NADH and CO₂
Anaerobic Respiration
When oxygen concentration is low, cells can still produce some ATP through anaerobic respiration.
Example: In mammals, pyruvate is converted to lactate during anaerobic conditions, allowing glycolysis to continue.
Anaerobic respiration in different organisms: • Mammals: Pyruvate → Lactate • Yeast and plants: Alcoholic fermentation
The Krebs Cycle
The Krebs cycle, also known as the citric acid cycle, is a series of reactions that complete the oxidation of glucose.
Vocabulary: Substrate-level phosphorylation - the production of ATP by direct transfer of a phosphate group from a substrate to ADP.
Key points of the Krebs cycle: • Occurs twice for each glucose molecule • Produces 4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP per glucose • ATP is produced via substrate-level phosphorylation
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
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