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5
0
ridita
10/12/2025
Biology
carbohydrates
606
•
10 Dec 2025
•
ridita
@ridita
Carbohydrates are essential biological molecules that come in three main... Show more
Monosaccharides are the building blocks of all carbohydrates - think of glucose, galactose, and fructose as the basic units. Glucose has two forms called isomers: α-glucose and β-glucose, which differ slightly in their structure but play very different roles in biology.
When two monosaccharides join together through a condensation reaction, they form a disaccharide and release a water molecule. This bond between them is called a glycosidic bond - you'll need to remember this term!
Common disaccharides include maltose , lactose , and sucrose . Each one forms through the same condensation process, creating that crucial glycosidic bond.
Key Point: The type of glycosidic bond determines whether the final polysaccharide will be straight, coiled, or branched - this affects its function!
Starch and glycogen are storage molecules that keep energy locked away until needed. Their coiled structure makes them compact, whilst being large enough that they can't accidentally leave the cell through the membrane.
Because they're insoluble, they won't mess with the cell's water potential - preventing dangerous osmotic problems. When energy is needed, hydrolysing enzymes attack the many ends of these branched molecules.
Cellulose is completely different - it's built for strength, not storage. Made from β-glucose with beta 1,4 glycosidic bonds, it forms straight chains that lie parallel to each other. These chains group together: microfibrils → macrofibrils → cell wall.
Glycogen has more branches than starch, meaning more ends for enzymes to attack. This allows animals to break it down faster - essential since animals have higher respiratory rates than plants.
Remember: Structure determines function - storage molecules are coiled and branched, whilst structural molecules like cellulose are straight and strong!
The Benedict's test detects reducing sugars and you'll definitely need to know this practical. Grind your sample with water, add equal amounts of Benedict's reagent, then heat gently in a water bath.
Reducing sugars (all monosaccharides and some disaccharides) will turn the solution from blue to orange-brown. The intensity tells you the concentration - from not present (blue) through low, medium, to high .
For non-reducing sugars, you need an extra step. Take your failed Benedict's test, get a fresh sample, add HCl to break down molecules, then neutralise with sodium hydrogen carbonate before doing Benedict's test again.
The iodine test for starch is beautifully simple - add potassium iodide drops to your sample and shake. Starch's coiled structure traps iodine, turning the solution from yellow to blue-black.
Exam Tip: Remember the colour changes - Benedict's goes blue to orange-brown, whilst iodine goes yellow to blue-black for starch!
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.
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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.
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
ridita
@ridita
Carbohydrates are essential biological molecules that come in three main sizes: monosaccharides (single sugars), disaccharides (double sugars), and polysaccharides (many sugars joined together). Understanding these structures and how to test for them is crucial for your A-level Biology exams.
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Monosaccharides are the building blocks of all carbohydrates - think of glucose, galactose, and fructose as the basic units. Glucose has two forms called isomers: α-glucose and β-glucose, which differ slightly in their structure but play very different roles in biology.
When two monosaccharides join together through a condensation reaction, they form a disaccharide and release a water molecule. This bond between them is called a glycosidic bond - you'll need to remember this term!
Common disaccharides include maltose , lactose , and sucrose . Each one forms through the same condensation process, creating that crucial glycosidic bond.
Key Point: The type of glycosidic bond determines whether the final polysaccharide will be straight, coiled, or branched - this affects its function!
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Starch and glycogen are storage molecules that keep energy locked away until needed. Their coiled structure makes them compact, whilst being large enough that they can't accidentally leave the cell through the membrane.
Because they're insoluble, they won't mess with the cell's water potential - preventing dangerous osmotic problems. When energy is needed, hydrolysing enzymes attack the many ends of these branched molecules.
Cellulose is completely different - it's built for strength, not storage. Made from β-glucose with beta 1,4 glycosidic bonds, it forms straight chains that lie parallel to each other. These chains group together: microfibrils → macrofibrils → cell wall.
Glycogen has more branches than starch, meaning more ends for enzymes to attack. This allows animals to break it down faster - essential since animals have higher respiratory rates than plants.
Remember: Structure determines function - storage molecules are coiled and branched, whilst structural molecules like cellulose are straight and strong!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Benedict's test detects reducing sugars and you'll definitely need to know this practical. Grind your sample with water, add equal amounts of Benedict's reagent, then heat gently in a water bath.
Reducing sugars (all monosaccharides and some disaccharides) will turn the solution from blue to orange-brown. The intensity tells you the concentration - from not present (blue) through low, medium, to high .
For non-reducing sugars, you need an extra step. Take your failed Benedict's test, get a fresh sample, add HCl to break down molecules, then neutralise with sodium hydrogen carbonate before doing Benedict's test again.
The iodine test for starch is beautifully simple - add potassium iodide drops to your sample and shake. Starch's coiled structure traps iodine, turning the solution from yellow to blue-black.
Exam Tip: Remember the colour changes - Benedict's goes blue to orange-brown, whilst iodine goes yellow to blue-black for starch!
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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Explore the structure and function of carbohydrates, including monosaccharides, disaccharides, and polysaccharides. This summary covers key concepts such as glycosidic bonds, condensation and hydrolysis reactions, and the roles of starch, glycogen, and cellulose in biological systems. Ideal for A Level Biology students studying biological molecules.
BiologyExplore the key types of polysaccharides, including cellulose, glycogen, and starch. This summary highlights their structures, bonding types, and biological significance, tailored for A-level Biology students. Understand the role of glycosidic bonds and the implications for digestion and energy storage.
BiologyExplore the fundamentals of biological molecules, including monomers, polymers, and carbohydrates. This summary covers key concepts such as monosaccharides, disaccharides, and the structure of glucose. Ideal for A-level Biology students seeking to understand the building blocks of life.
BiologyExplore the essential characteristics of monosaccharides, including their structure, types (pentose and hexose), and properties such as solubility in water. This summary highlights key concepts like glucose, fructose, and galactose, and explains the significance of hydrogen bonding in their hydrophilic nature. Ideal for students studying biological molecules.
BiologyExplore the diverse structures and functions of carbohydrates, including monosaccharides like glucose and fructose, disaccharides such as sucrose and lactose, and polysaccharides like starch and cellulose. This summary covers key concepts such as glycosidic bonds, hydrophilicity, and the role of carbohydrates in biological systems. Ideal for students studying biomolecules and macromolecules.
BiologyExplore the mechanisms of carbohydrate formation, including condensation and hydrolysis reactions. This summary covers the structure of polysaccharides like amylose and amylopectin, the types of glycosidic bonds, and the formation of disaccharides such as lactose, maltose, and sucrose. Ideal for A-level biology students studying biomolecules and macromolecules.
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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.
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