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21 Jan 2026
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Comprehensive Biology Mind Maps: Biological Molecules and Enzymes for IGCSE Edexcel
lemon_socks94
@water_lily_butterfly
1 / 4
Biological Molecules: The Building Blocks of Life
Your body runs on three main types of biological molecules, and each one has a specific job to do. Think of them as different tools in a toolbox - each perfectly designed for their role.
Carbohydrates are your body's favourite fuel source. They're made from carbon, hydrogen, and oxygen atoms arranged in different ways. The simplest ones are called monosaccharides (like glucose), which are sweet and dissolve easily in water. When two of these join together, you get disaccharides like sucrose (table sugar). Chain loads of them together and you get polysaccharides like starch - these aren't sweet and don't dissolve easily.
Proteins are the workhorses of your cells. Made from carbon, hydrogen, oxygen, and nitrogen, they're built from 20 different amino acids that can be arranged in countless ways. Proteins handle growth, repair, and act as enzymes, hormones, and structural support - basically, they keep everything running smoothly.
Quick Tip: Remember that glucose + oxygen = carbon dioxide + water + ENERGY - this is how your cells get power!
Lipids (fats) are your long-term energy storage and insulation. They're made from carbon, hydrogen, and oxygen, but arranged differently than carbs. Each lipid has one glycerol molecule attached to three fatty acids - think of it like a three-pronged fork.
Enzymes: Your Body's Speed Boosters
Enzymes are special proteins that act as biological catalysts - they speed up chemical reactions without getting used up themselves. Every single reaction in your body needs its own specific enzyme to work properly.
Each enzyme has a unique 3D shape with a special pocket called the active site. This is where the magic happens. Substrates (the molecules being changed) fit into this site like a key in a lock - they must be complementary to work. When they bind together, they form an enzyme-substrate complex, the reaction happens, and products are released.
Temperature and pH massively affect how well enzymes work. Each enzyme has an optimum temperature and pH where it works fastest. Too hot, too cold, too acidic, or too alkaline, and the enzyme becomes denatured - its shape changes and it stops working completely.
Remember: Higher temperature means molecules move faster and collide more often, speeding up reactions - but only up to the optimum point!
Understanding enzymes is crucial because they control every chemical process in your body, from digesting food to building new cells. Without them, these reactions would be far too slow to sustain life.
Food Tests: Detecting What's in Your Meals
Want to become a food detective? These simple food tests let you identify which biological molecules are hiding in different foods using colour-changing reactions.
The Benedict's test reveals glucose and other reducing sugars. Start with a blue solution, heat it with your sample, and watch for a colour change. Brick red means loads of glucose is present, whilst green indicates just a tiny amount. No change? No glucose there.
For starch, use the iodine test - dead simple and super reliable. Add orange iodine solution to your sample. If it turns blue-black, starch is present. Stays orange? No starch detected.
Lab Safety: Always wear safety goggles when heating solutions and handling chemicals like iodine!
The Biuret test hunts down proteins using two solutions. Mix your sample with sodium hydroxide, then add copper sulphate. Purple or lilac colour means protein is there, whilst blue means it's absent.
Finally, the emulsion test spots lipids by mixing your sample with ethanol, then pouring it into cold water. A cloudy white emulsion forming means fats are present - if it stays clear, there are no lipids.
Enzyme Investigation: Measuring Reaction Rates
Time to put your enzyme knowledge into practice! This investigation shows how temperature and pH affect enzyme activity by measuring oxygen production from hydrogen peroxide breakdown.
Set up your experiment with test tubes containing the enzyme catalase at different temperatures in water baths. Use an inverted measuring cylinder to collect oxygen gas and measure how much is produced per minute. The independent variable is temperature, the dependent variable is oxygen produced, and you'll control pH and enzyme concentration.
For the pH investigation, prepare test tubes with solutions at different pH levels (pH 4, 5, 6, 7, 8). Test each one and time how long substrates take to disappear - measure every 10 seconds for accuracy.
Practical Tip: Always use the same volume of enzyme solution and substrate to make your results fair and comparable!
Watch for the optimum conditions where the enzyme works fastest. You'll see reaction rates increase with temperature up to a point, then suddenly drop off when the enzyme denatures. Each enzyme has its own perfect pH too.
This investigation perfectly demonstrates how enzymes are affected by their environment and why your body works so hard to maintain stable temperature and pH levels.
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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.
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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
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Sudenaz Ocak
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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
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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 Knowunity AI. 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 Knowunity AI. 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
Comprehensive Biology Mind Maps: Biological Molecules and Enzymes for IGCSE Edexcel
lemon_socks94
@water_lily_butterfly
Ever wondered how your body breaks down that chocolate bar or why bread tastes sweet when you chew it? It's all down to biological molecules - the building blocks that keep you alive and functioning every single day.
Biological Molecules: The Building Blocks of Life
Your body runs on three main types of biological molecules, and each one has a specific job to do. Think of them as different tools in a toolbox - each perfectly designed for their role.
Carbohydrates are your body's favourite fuel source. They're made from carbon, hydrogen, and oxygen atoms arranged in different ways. The simplest ones are called monosaccharides (like glucose), which are sweet and dissolve easily in water. When two of these join together, you get disaccharides like sucrose (table sugar). Chain loads of them together and you get polysaccharides like starch - these aren't sweet and don't dissolve easily.
Proteins are the workhorses of your cells. Made from carbon, hydrogen, oxygen, and nitrogen, they're built from 20 different amino acids that can be arranged in countless ways. Proteins handle growth, repair, and act as enzymes, hormones, and structural support - basically, they keep everything running smoothly.
Quick Tip: Remember that glucose + oxygen = carbon dioxide + water + ENERGY - this is how your cells get power!
Lipids (fats) are your long-term energy storage and insulation. They're made from carbon, hydrogen, and oxygen, but arranged differently than carbs. Each lipid has one glycerol molecule attached to three fatty acids - think of it like a three-pronged fork.
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Enzymes: Your Body's Speed Boosters
Enzymes are special proteins that act as biological catalysts - they speed up chemical reactions without getting used up themselves. Every single reaction in your body needs its own specific enzyme to work properly.
Each enzyme has a unique 3D shape with a special pocket called the active site. This is where the magic happens. Substrates (the molecules being changed) fit into this site like a key in a lock - they must be complementary to work. When they bind together, they form an enzyme-substrate complex, the reaction happens, and products are released.
Temperature and pH massively affect how well enzymes work. Each enzyme has an optimum temperature and pH where it works fastest. Too hot, too cold, too acidic, or too alkaline, and the enzyme becomes denatured - its shape changes and it stops working completely.
Remember: Higher temperature means molecules move faster and collide more often, speeding up reactions - but only up to the optimum point!
Understanding enzymes is crucial because they control every chemical process in your body, from digesting food to building new cells. Without them, these reactions would be far too slow to sustain life.
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Improve your grades
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Food Tests: Detecting What's in Your Meals
Want to become a food detective? These simple food tests let you identify which biological molecules are hiding in different foods using colour-changing reactions.
The Benedict's test reveals glucose and other reducing sugars. Start with a blue solution, heat it with your sample, and watch for a colour change. Brick red means loads of glucose is present, whilst green indicates just a tiny amount. No change? No glucose there.
For starch, use the iodine test - dead simple and super reliable. Add orange iodine solution to your sample. If it turns blue-black, starch is present. Stays orange? No starch detected.
Lab Safety: Always wear safety goggles when heating solutions and handling chemicals like iodine!
The Biuret test hunts down proteins using two solutions. Mix your sample with sodium hydroxide, then add copper sulphate. Purple or lilac colour means protein is there, whilst blue means it's absent.
Finally, the emulsion test spots lipids by mixing your sample with ethanol, then pouring it into cold water. A cloudy white emulsion forming means fats are present - if it stays clear, there are no lipids.
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
Enzyme Investigation: Measuring Reaction Rates
Time to put your enzyme knowledge into practice! This investigation shows how temperature and pH affect enzyme activity by measuring oxygen production from hydrogen peroxide breakdown.
Set up your experiment with test tubes containing the enzyme catalase at different temperatures in water baths. Use an inverted measuring cylinder to collect oxygen gas and measure how much is produced per minute. The independent variable is temperature, the dependent variable is oxygen produced, and you'll control pH and enzyme concentration.
For the pH investigation, prepare test tubes with solutions at different pH levels (pH 4, 5, 6, 7, 8). Test each one and time how long substrates take to disappear - measure every 10 seconds for accuracy.
Practical Tip: Always use the same volume of enzyme solution and substrate to make your results fair and comparable!
Watch for the optimum conditions where the enzyme works fastest. You'll see reaction rates increase with temperature up to a point, then suddenly drop off when the enzyme denatures. Each enzyme has its own perfect pH too.
This investigation perfectly demonstrates how enzymes are affected by their environment and why your body works so hard to maintain stable temperature and pH levels.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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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.
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iOS user
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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.
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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 Knowunity AI. 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