Subjects
Maths
Biology
Chemistry
English Language
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Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
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1l the quest for political stability: germany, 1871-1991
Britain & the wider world: 1745 -1901
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
World war one
Britain: 1509 -1745
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Biology
4 Dec 2025
553
4 pages
Enzymes are absolutely crucial for keeping you alive - they speed up thousands of reactions happening in your... Show more
Ever wondered how your body manages to carry out complex reactions at just 37°C? Enzymes are globular proteins that act as biological catalysts, speeding up metabolic reactions that would otherwise be impossibly slow at body temperature.
These molecular machines work both intracellularly (inside cells) and extracellularly (outside cells). For example, catalase breaks down harmful hydrogen peroxide inside your cells, whilst digestive enzymes like amylase work in your gut to break down food.
The lock and key hypothesis explains enzyme specificity - each enzyme has a uniquely shaped active site that perfectly matches its substrate, like a key fitting into a lock. This three-dimensional shape comes from the enzyme's tertiary structure, determined by its specific amino acid sequence.
Key Insight The induced-fit hypothesis is more accurate than lock and key - the active site actually changes shape slightly when the substrate binds, reducing the activation energy needed for the reaction to occur.
The induced-fit hypothesis reveals how enzymes actually reduce activation energy. When a substrate approaches the active site, it doesn't fit perfectly at first - instead, the binding causes both the enzyme and substrate to change shape slightly, creating the perfect fit and weakening bonds in the substrate.
This creates the enzyme-substrate complex (ESC), which then becomes the enzyme-product complex before releasing the product. The enzyme remains unchanged and ready for another reaction cycle - that's why they're such efficient catalysts!
pH levels dramatically affect enzyme activity because hydrogen ions interfere with the protein's structure. Each enzyme has an optimum pH - stray too far from this, and the active site changes shape, denaturing the enzyme permanently.
Remember Denaturation is irreversible! Once an enzyme loses its shape due to extreme pH, it can never function again.
Temperature effects follow a predictable pattern - initially, higher temperatures increase reaction rates as molecules move faster and collide more frequently, but beyond the optimum temperature, enzymes denature as their bonds break.
Understanding temperature's dual effect on enzymes is crucial for your exams. At low temperatures , enzyme activity increases because molecules gain kinetic energy and collide more frequently with substrates. However, once you exceed the optimum temperature, disaster strikes!
High temperatures cause enzyme molecules to vibrate violently, breaking the hydrogen bonds and ionic bonds that maintain the protein's 3D structure. The enzyme becomes denatured - its active site permanently loses its complementary shape to the substrate.
Enzyme concentration directly affects reaction rate - more enzymes mean more active sites available for substrate binding. It's like having more checkout tills open at a supermarket - more customers get served per minute!
Substrate concentration also boosts reaction rates initially, but there's a catch. Once all enzyme active sites are occupied, the reaction plateaus regardless of how much more substrate you add - the enzymes become the limiting factor.
Exam Tip Remember that both enzyme and substrate concentration effects level off - enzyme concentration plateaus when substrate runs out, substrate concentration plateaus when all active sites are occupied.
When investigating enzyme activity experimentally, precision matters! You'll need to control temperature using a thermostatic water bath, maintain pH with buffer solutions, and ensure reliability by repeating tests multiple times and calculating means.
Your control experiment should omit the enzyme entirely - this proves that no reaction occurs without the catalyst present. Don't forget to stir solutions regularly for even distribution and consider what level of precision is appropriate for your measurements.
Coenzymes and cofactors act as enzyme helpers, though they work differently. Coenzymes are larger organic molecules (often made from B vitamins) that transfer substances between enzymes - like coenzyme A in respiration and NAD in hydrogen transport.
Cofactors are inorganic metal ions that bind to active sites, making enzyme-substrate complex formation quicker and easier. Examples include chloride ions in amylase and zinc ions in carbonic anhydrase.
Competitive inhibitors are the troublemakers of enzyme chemistry! These molecules have similar shapes to the natural substrate and compete for the same active site, reducing reaction rates by blocking substrate access.
Quick Check The amount of competitive inhibition depends on the relative concentrations of inhibitor versus substrate - more inhibitor means more blocked active sites!
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.
8
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential role of enzymes in biochemical reactions, including their structure, function, and mechanisms of action. This summary covers key concepts such as the active site, enzyme specificity, types of inhibitors, and factors affecting enzyme activity. Ideal for A-Level students seeking a comprehensive overview of enzymatic processes.
BiologyExplore the mechanisms of enzyme inhibitors, focusing on competitive and non-competitive inhibition. This summary covers key concepts such as the active site, allosteric site, and the enzyme-substrate complex, providing insights into how inhibitors affect reaction rates. Ideal for students studying biological molecules.
BiologyExplore the mechanisms of cyanide poisoning and the role of enzymes in biological processes. This study note covers key concepts such as enzyme-substrate interactions, the impact of cyanide on cellular respiration, and the importance of maintaining homeostasis. Ideal for AQA Biology students preparing for exams, this resource includes past paper questions and detailed explanations of enzyme activity and DNA replication.
BiologyExplore the role of enzymes as biological catalysts, including the enzyme-substrate complex, induced fit model, and types of inhibition (competitive and non-competitive). This summary covers key concepts such as enzyme concentration, reaction rates, and the impact of pH on enzyme activity, tailored for AQA specifications.
BiologyExplore essential methods for crop protection in higher biology, including pest control techniques, the impact of weeds, plant diseases, and the principles of integrated pest management. This summary covers key concepts such as bioaccumulation, biomagnification, and the use of pesticides, providing a comprehensive overview for students studying plant health and productivity.
BiologyExplore the role of enzymes as biological catalysts in digestion, including key digestive enzymes like amylase, proteases, and lipases. Understand how temperature and pH affect enzyme activity and the concept of denaturation. This summary provides essential insights for biology students studying enzyme kinetics and digestion.
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
Enzymes are absolutely crucial for keeping you alive - they speed up thousands of reactions happening in your body right now! These protein catalysts make reactions occur fast enough at body temperature to sustain life, from digesting your breakfast to... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered how your body manages to carry out complex reactions at just 37°C? Enzymes are globular proteins that act as biological catalysts, speeding up metabolic reactions that would otherwise be impossibly slow at body temperature.
These molecular machines work both intracellularly (inside cells) and extracellularly (outside cells). For example, catalase breaks down harmful hydrogen peroxide inside your cells, whilst digestive enzymes like amylase work in your gut to break down food.
The lock and key hypothesis explains enzyme specificity - each enzyme has a uniquely shaped active site that perfectly matches its substrate, like a key fitting into a lock. This three-dimensional shape comes from the enzyme's tertiary structure, determined by its specific amino acid sequence.
Key Insight: The induced-fit hypothesis is more accurate than lock and key - the active site actually changes shape slightly when the substrate binds, reducing the activation energy needed for the reaction to occur.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The induced-fit hypothesis reveals how enzymes actually reduce activation energy. When a substrate approaches the active site, it doesn't fit perfectly at first - instead, the binding causes both the enzyme and substrate to change shape slightly, creating the perfect fit and weakening bonds in the substrate.
This creates the enzyme-substrate complex (ESC), which then becomes the enzyme-product complex before releasing the product. The enzyme remains unchanged and ready for another reaction cycle - that's why they're such efficient catalysts!
pH levels dramatically affect enzyme activity because hydrogen ions interfere with the protein's structure. Each enzyme has an optimum pH - stray too far from this, and the active site changes shape, denaturing the enzyme permanently.
Remember: Denaturation is irreversible! Once an enzyme loses its shape due to extreme pH, it can never function again.
Temperature effects follow a predictable pattern - initially, higher temperatures increase reaction rates as molecules move faster and collide more frequently, but beyond the optimum temperature, enzymes denature as their bonds break.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Understanding temperature's dual effect on enzymes is crucial for your exams. At low temperatures , enzyme activity increases because molecules gain kinetic energy and collide more frequently with substrates. However, once you exceed the optimum temperature, disaster strikes!
High temperatures cause enzyme molecules to vibrate violently, breaking the hydrogen bonds and ionic bonds that maintain the protein's 3D structure. The enzyme becomes denatured - its active site permanently loses its complementary shape to the substrate.
Enzyme concentration directly affects reaction rate - more enzymes mean more active sites available for substrate binding. It's like having more checkout tills open at a supermarket - more customers get served per minute!
Substrate concentration also boosts reaction rates initially, but there's a catch. Once all enzyme active sites are occupied, the reaction plateaus regardless of how much more substrate you add - the enzymes become the limiting factor.
Exam Tip: Remember that both enzyme and substrate concentration effects level off - enzyme concentration plateaus when substrate runs out, substrate concentration plateaus when all active sites are occupied.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When investigating enzyme activity experimentally, precision matters! You'll need to control temperature using a thermostatic water bath, maintain pH with buffer solutions, and ensure reliability by repeating tests multiple times and calculating means.
Your control experiment should omit the enzyme entirely - this proves that no reaction occurs without the catalyst present. Don't forget to stir solutions regularly for even distribution and consider what level of precision is appropriate for your measurements.
Coenzymes and cofactors act as enzyme helpers, though they work differently. Coenzymes are larger organic molecules (often made from B vitamins) that transfer substances between enzymes - like coenzyme A in respiration and NAD in hydrogen transport.
Cofactors are inorganic metal ions that bind to active sites, making enzyme-substrate complex formation quicker and easier. Examples include chloride ions in amylase and zinc ions in carbonic anhydrase.
Competitive inhibitors are the troublemakers of enzyme chemistry! These molecules have similar shapes to the natural substrate and compete for the same active site, reducing reaction rates by blocking substrate access.
Quick Check: The amount of competitive inhibition depends on the relative concentrations of inhibitor versus substrate - more inhibitor means more blocked active sites!
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.
8
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential role of enzymes in biochemical reactions, including their structure, function, and mechanisms of action. This summary covers key concepts such as the active site, enzyme specificity, types of inhibitors, and factors affecting enzyme activity. Ideal for A-Level students seeking a comprehensive overview of enzymatic processes.
BiologyExplore the mechanisms of enzyme inhibitors, focusing on competitive and non-competitive inhibition. This summary covers key concepts such as the active site, allosteric site, and the enzyme-substrate complex, providing insights into how inhibitors affect reaction rates. Ideal for students studying biological molecules.
BiologyExplore the mechanisms of cyanide poisoning and the role of enzymes in biological processes. This study note covers key concepts such as enzyme-substrate interactions, the impact of cyanide on cellular respiration, and the importance of maintaining homeostasis. Ideal for AQA Biology students preparing for exams, this resource includes past paper questions and detailed explanations of enzyme activity and DNA replication.
BiologyExplore the role of enzymes as biological catalysts, including the enzyme-substrate complex, induced fit model, and types of inhibition (competitive and non-competitive). This summary covers key concepts such as enzyme concentration, reaction rates, and the impact of pH on enzyme activity, tailored for AQA specifications.
BiologyExplore essential methods for crop protection in higher biology, including pest control techniques, the impact of weeds, plant diseases, and the principles of integrated pest management. This summary covers key concepts such as bioaccumulation, biomagnification, and the use of pesticides, providing a comprehensive overview for students studying plant health and productivity.
BiologyExplore the role of enzymes as biological catalysts in digestion, including key digestive enzymes like amylase, proteases, and lipases. Understand how temperature and pH affect enzyme activity and the concept of denaturation. This summary provides essential insights for biology students studying enzyme kinetics and digestion.
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
