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Updated Mar 30, 2026
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Cell Diffusion: Year 11 Biology Summary Notes
izzy
@isabelmay
Understanding Diffusion
Think of diffusion as nature's way of mixing things up. Diffusion is the movement of molecules from areas where there's loads of them to areas where there's fewer - basically from high concentration to low concentration.
The clever bit is that whilst particles move in all directions, there's always a net movement from the crowded area to the less crowded one. It's like people spreading out at a party - they naturally move from the packed kitchen to the emptier living room.
Several factors speed up or slow down this process. A steeper concentration gradient (bigger difference between high and low areas) means faster diffusion. Higher temperature gives particles more energy to move about quickly. Plus, having a larger surface area means more space for molecules to cross through.
Quick Tip: Remember that diffusion happens naturally - no energy required from the cell!
Diffusion in Your Body
Your body relies on diffusion constantly, especially in your lungs and liver. In your lungs, blood arriving from your body is packed with CO₂ but low on oxygen. The clever design of alveoli (tiny air sacs) allows CO₂ to diffuse out into the air you breathe out, whilst oxygen diffuses from the air into your blood.
Your liver cells use diffusion differently. Urea (a waste product) builds up to high concentrations inside liver cells, then diffuses out into nearby blood vessels. From there, your kidneys filter it out completely.
Every single cell in your body depends on diffusion for survival. Oxygen diffuses into cells where it's needed for respiration, whilst CO₂ (the waste product) diffuses out to be carried away by your blood.
Real-world connection: This is why exercise makes you breathe harder - your cells need more oxygen and produce more CO₂!
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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.
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Best app on earth! no words because it’s too good
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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.
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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!
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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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iOS user
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Cell Diffusion: Year 11 Biology Summary Notes
izzy
@isabelmay
Ever wondered how oxygen gets into your blood or how waste products leave your cells? It's all down to diffusion - a simple but essential process that keeps every cell in your body functioning properly.
Understanding Diffusion
Think of diffusion as nature's way of mixing things up. Diffusion is the movement of molecules from areas where there's loads of them to areas where there's fewer - basically from high concentration to low concentration.
The clever bit is that whilst particles move in all directions, there's always a net movement from the crowded area to the less crowded one. It's like people spreading out at a party - they naturally move from the packed kitchen to the emptier living room.
Several factors speed up or slow down this process. A steeper concentration gradient (bigger difference between high and low areas) means faster diffusion. Higher temperature gives particles more energy to move about quickly. Plus, having a larger surface area means more space for molecules to cross through.
Quick Tip: Remember that diffusion happens naturally - no energy required from the cell!
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Diffusion in Your Body
Your body relies on diffusion constantly, especially in your lungs and liver. In your lungs, blood arriving from your body is packed with CO₂ but low on oxygen. The clever design of alveoli (tiny air sacs) allows CO₂ to diffuse out into the air you breathe out, whilst oxygen diffuses from the air into your blood.
Your liver cells use diffusion differently. Urea (a waste product) builds up to high concentrations inside liver cells, then diffuses out into nearby blood vessels. From there, your kidneys filter it out completely.
Every single cell in your body depends on diffusion for survival. Oxygen diffuses into cells where it's needed for respiration, whilst CO₂ (the waste product) diffuses out to be carried away by your blood.
Real-world connection: This is why exercise makes you breathe harder - your cells need more oxygen and produce more CO₂!
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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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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