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3 Dec 2025
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Key Biological Molecules Explained
Annlisa
@iaminsane
1 / 4
Elements and Bonding Basics
Think of elements as the basic building blocks of everything alive - including you! Elements are defined by how many protons sit in their nucleus, and all living things rely on just four key players.
The fantastic four elements are carbon, hydrogen, nitrogen, and oxygen (remember CHNO). When these atoms team up by sharing electrons, they form covalent bonds and create molecules - the compounds that actually do the work in your body.
Each element has strict bonding rules: carbon makes 4 bonds, nitrogen makes 3, oxygen makes 2, and hydrogen makes just 1. It's like each atom has a specific number of hands to hold onto others! Water (H₂O), carbon dioxide (CO₂), and methane (CH₄) are perfect examples of how these bonding rules play out in real molecules.
Quick Tip: Remember the bonding numbers by thinking "C-4-yourself, N-3-eds company, O-2-gether, H-1-and only!"
Water Structure and Hydrogen Bonding
Water isn't just boring H₂O - it's actually a polar molecule with a personality! The oxygen atom is a bit greedy and pulls the shared electrons closer, making itself slightly negative (δ-) whilst leaving the hydrogen atoms slightly positive (δ+).
This creates a dipolar molecule with different charged regions. The slightly negative oxygen of one water molecule attracts the slightly positive hydrogen of another, forming hydrogen bonds. These bonds are individually weak but incredibly powerful when working together.
Hydrogen bonding explains why water behaves so uniquely - from its high boiling point to its ability to dissolve so many substances. The angle between the hydrogen atoms is exactly 104.5°, creating water's distinctive bent shape that makes all its amazing properties possible.
Remember: Hydrogen bonds are like weak handshakes that constantly break and reform, but when millions work together, they create water's incredible strength!
Carbohydrates - Your Body's Fuel
Carbohydrates are your body's preferred energy source, made from just carbon, hydrogen, and oxygen with the general formula CₓH₂Oᵧ. They're also called saccharides or sugars, and they come in three main sizes.
Monosaccharides are single sugar units like glucose and fructose - think of them as individual Lego blocks. Disaccharides form when two monosaccharides join together (like lactose in milk), whilst polysaccharides are long chains that create storage molecules like glycogen and structural compounds like cellulose.
Glucose (C₆H₁₂O₆) is the star player here - it's a hexose sugar with six carbons that comes in two forms: alpha and beta glucose (these are isomers). Because glucose is polar, it dissolves easily in water, allowing it to travel through your bloodstream and into cells where it's converted to ATP energy.
Study Hack: Think "mono = one sugar, di = two sugars, poly = many sugars" - just like monologue, dialogue, and polygon!
Lipids - Fats and Oils Explained
Lipids (fats and oils) are the misunderstood molecules of biology - they're actually essential for insulation, energy storage, and cell membranes. Unlike carbs, lipids are hydrophobic and non-polar, which is why oil and water never mix.
The most common lipids are triglycerides, made from one glycerol molecule bonded to three fatty acids. Glycerol acts like a backbone with three attachment points, each connected to a fatty acid chain through ester bonds formed during esterification.
During esterification, the hydroxyl groups from glycerol react with the carboxyl groups from fatty acids, releasing three water molecules in the process. This condensation reaction creates the stable ester bonds that hold triglycerides together until enzymes like lipase break them down for energy.
Key Insight: Lipids store more than twice the energy per gram compared to carbs - that's why your body saves them for long-term energy storage!
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Anna
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Best app on earth! no words because it’s too good
Thomas R
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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.
Basil
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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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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
Key Biological Molecules Explained
Annlisa
@iaminsane
Your body is essentially a complex chemistry set, and understanding the key biological molecules is like learning the ingredients that make life possible. From the water that fills your cells to the carbs that fuel your brain and the fats... Show more
Elements and Bonding Basics
Think of elements as the basic building blocks of everything alive - including you! Elements are defined by how many protons sit in their nucleus, and all living things rely on just four key players.
The fantastic four elements are carbon, hydrogen, nitrogen, and oxygen (remember CHNO). When these atoms team up by sharing electrons, they form covalent bonds and create molecules - the compounds that actually do the work in your body.
Each element has strict bonding rules: carbon makes 4 bonds, nitrogen makes 3, oxygen makes 2, and hydrogen makes just 1. It's like each atom has a specific number of hands to hold onto others! Water (H₂O), carbon dioxide (CO₂), and methane (CH₄) are perfect examples of how these bonding rules play out in real molecules.
Quick Tip: Remember the bonding numbers by thinking "C-4-yourself, N-3-eds company, O-2-gether, H-1-and only!"
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Water Structure and Hydrogen Bonding
Water isn't just boring H₂O - it's actually a polar molecule with a personality! The oxygen atom is a bit greedy and pulls the shared electrons closer, making itself slightly negative (δ-) whilst leaving the hydrogen atoms slightly positive (δ+).
This creates a dipolar molecule with different charged regions. The slightly negative oxygen of one water molecule attracts the slightly positive hydrogen of another, forming hydrogen bonds. These bonds are individually weak but incredibly powerful when working together.
Hydrogen bonding explains why water behaves so uniquely - from its high boiling point to its ability to dissolve so many substances. The angle between the hydrogen atoms is exactly 104.5°, creating water's distinctive bent shape that makes all its amazing properties possible.
Remember: Hydrogen bonds are like weak handshakes that constantly break and reform, but when millions work together, they create water's incredible strength!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Carbohydrates - Your Body's Fuel
Carbohydrates are your body's preferred energy source, made from just carbon, hydrogen, and oxygen with the general formula CₓH₂Oᵧ. They're also called saccharides or sugars, and they come in three main sizes.
Monosaccharides are single sugar units like glucose and fructose - think of them as individual Lego blocks. Disaccharides form when two monosaccharides join together (like lactose in milk), whilst polysaccharides are long chains that create storage molecules like glycogen and structural compounds like cellulose.
Glucose (C₆H₁₂O₆) is the star player here - it's a hexose sugar with six carbons that comes in two forms: alpha and beta glucose (these are isomers). Because glucose is polar, it dissolves easily in water, allowing it to travel through your bloodstream and into cells where it's converted to ATP energy.
Study Hack: Think "mono = one sugar, di = two sugars, poly = many sugars" - just like monologue, dialogue, and polygon!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Lipids - Fats and Oils Explained
Lipids (fats and oils) are the misunderstood molecules of biology - they're actually essential for insulation, energy storage, and cell membranes. Unlike carbs, lipids are hydrophobic and non-polar, which is why oil and water never mix.
The most common lipids are triglycerides, made from one glycerol molecule bonded to three fatty acids. Glycerol acts like a backbone with three attachment points, each connected to a fatty acid chain through ester bonds formed during esterification.
During esterification, the hydroxyl groups from glycerol react with the carboxyl groups from fatty acids, releasing three water molecules in the process. This condensation reaction creates the stable ester bonds that hold triglycerides together until enzymes like lipase break them down for energy.
Key Insight: Lipids store more than twice the energy per gram compared to carbs - that's why your body saves them for long-term energy storage!
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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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