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3 Dec 2025
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Water and Inorganic Ions: Key AS Biology Notes
jessica sweeney
@jessicasweeney_fdpf
1 / 5
The Building Blocks of Life
Your body is essentially a walking chemistry set! Organic molecules make up about 93% of your dry body mass, and they fall into four main groups: carbohydrates, proteins, lipids, and nucleic acids. The remaining 7% consists of small inorganic molecules and ions.
But here's the amazing bit - nearly all the chemical reactions that keep you alive happen in water. Water isn't just there for the ride; it's actively involved as a solvent where reactions occur and often as a product of these reactions.
Water molecules are special because they form hydrogen bonds with each other. The hydrogen atoms carry a slight positive charge whilst the oxygen carries a slight negative charge, creating an attraction between different water molecules.
Quick Fact: Each water molecule can form hydrogen bonds with up to 4 other water molecules, creating a network that gives water its unique properties!
Water as Nature's Ultimate Solvent
Water's polarity (uneven distribution of charges) makes it brilliant at dissolving other substances. When you add charged molecules like ions or amino acids to water, the polar water molecules cluster around them like a protective shield.
Hydrogen bonds in water have four key features: they form between adjacent water molecules (specifically between oxygen and hydrogen atoms), each water molecule can bond with up to four others, and they're relatively weak so they break and reform easily.
This makes water an exceptional solvent because most cellular reactions need to happen in aqueous solution. Water also acts as a transparent medium in living organisms, which is pretty handy for things like your eyeballs!
Hydrophilic substances (like salts) love water and dissolve easily, whilst hydrophobic substances (like oils) hate water and won't dissolve.
Remember: If it dissolves in water, it's hydrophilic. If it repels water, it's hydrophobic!
Water's Superpowers
Water's hydrogen bonding gives it some incredible properties that make life possible. Although individual hydrogen bonds are weak, collectively they make water remarkably stable.
Water has an unusually high specific heat capacity - it takes loads of energy to heat up just 1kg of water by 1°C. This helps regulate your body temperature and keeps Earth's climate stable.
The weakness of individual bonds means water molecules constantly jostle each other in the liquid phase, giving water its molecular mobility. Here's something weird though - water actually expands when it freezes! As it gets colder, molecules slow down and need more space to form the maximum number of hydrogen bonds.
This is why ice floats and why frozen pipes burst. Without this property, lakes would freeze from the bottom up, killing all aquatic life.
Cool Fact: Water's expansion when freezing is why ice floats - if it didn't, entire ecosystems would collapse!
Buffers and pH Control
Your body needs to maintain a stable pH, and that's where buffers come in. A buffer is a substance that resists pH changes when acids or bases are added to it. Think of buffers as pH bodyguards!
Hydrogen carbonate ions and blood proteins like albumin act as natural buffers in your body. This is absolutely crucial because enzymes (which are proteins) need their specific 3D shape to work properly.
If the pH changes too much, enzymes become denatured - they lose their shape and stop working. That's why buffers are essential in enzyme practicals and why your body works so hard to maintain pH balance.
Inorganic ions are equally important for structure and metabolism. These charged particles have lost or gained electrons, and many dissolve easily in water where they can do their jobs.
Key Point: Without buffers, even small pH changes would denature your enzymes and stop vital reactions!
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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.
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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
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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
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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
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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
Water and Inorganic Ions: Key AS Biology Notes
jessica sweeney
@jessicasweeney_fdpf
Ever wondered what makes up living things? About 80% of your body is water, but the remaining 20% contains some fascinating molecules that keep you alive. Let's explore the essential building blocks of life and discover why water is absolutely... Show more
The Building Blocks of Life
Your body is essentially a walking chemistry set! Organic molecules make up about 93% of your dry body mass, and they fall into four main groups: carbohydrates, proteins, lipids, and nucleic acids. The remaining 7% consists of small inorganic molecules and ions.
But here's the amazing bit - nearly all the chemical reactions that keep you alive happen in water. Water isn't just there for the ride; it's actively involved as a solvent where reactions occur and often as a product of these reactions.
Water molecules are special because they form hydrogen bonds with each other. The hydrogen atoms carry a slight positive charge whilst the oxygen carries a slight negative charge, creating an attraction between different water molecules.
Quick Fact: Each water molecule can form hydrogen bonds with up to 4 other water molecules, creating a network that gives water its unique properties!
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Water as Nature's Ultimate Solvent
Water's polarity (uneven distribution of charges) makes it brilliant at dissolving other substances. When you add charged molecules like ions or amino acids to water, the polar water molecules cluster around them like a protective shield.
Hydrogen bonds in water have four key features: they form between adjacent water molecules (specifically between oxygen and hydrogen atoms), each water molecule can bond with up to four others, and they're relatively weak so they break and reform easily.
This makes water an exceptional solvent because most cellular reactions need to happen in aqueous solution. Water also acts as a transparent medium in living organisms, which is pretty handy for things like your eyeballs!
Hydrophilic substances (like salts) love water and dissolve easily, whilst hydrophobic substances (like oils) hate water and won't dissolve.
Remember: If it dissolves in water, it's hydrophilic. If it repels water, it's hydrophobic!
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Water's Superpowers
Water's hydrogen bonding gives it some incredible properties that make life possible. Although individual hydrogen bonds are weak, collectively they make water remarkably stable.
Water has an unusually high specific heat capacity - it takes loads of energy to heat up just 1kg of water by 1°C. This helps regulate your body temperature and keeps Earth's climate stable.
The weakness of individual bonds means water molecules constantly jostle each other in the liquid phase, giving water its molecular mobility. Here's something weird though - water actually expands when it freezes! As it gets colder, molecules slow down and need more space to form the maximum number of hydrogen bonds.
This is why ice floats and why frozen pipes burst. Without this property, lakes would freeze from the bottom up, killing all aquatic life.
Cool Fact: Water's expansion when freezing is why ice floats - if it didn't, entire ecosystems would collapse!
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Buffers and pH Control
Your body needs to maintain a stable pH, and that's where buffers come in. A buffer is a substance that resists pH changes when acids or bases are added to it. Think of buffers as pH bodyguards!
Hydrogen carbonate ions and blood proteins like albumin act as natural buffers in your body. This is absolutely crucial because enzymes (which are proteins) need their specific 3D shape to work properly.
If the pH changes too much, enzymes become denatured - they lose their shape and stop working. That's why buffers are essential in enzyme practicals and why your body works so hard to maintain pH balance.
Inorganic ions are equally important for structure and metabolism. These charged particles have lost or gained electrons, and many dissolve easily in water where they can do their jobs.
Key Point: Without buffers, even small pH changes would denature your enzymes and stop vital reactions!
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We thought you’d never ask...
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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