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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
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Biology
3 Dec 2025
44
3 pages
Kadiok @kadiokee
Cell membranes aren't just simple barriers - they're complex, dynamic structures that control everything entering and leaving your... Show more
Think of cell membranes as a flexible sandwich made primarily of phospholipids arranged in a bilayer. Each phospholipid has a hydrophilic phosphate head (loves water) and hydrophobic fatty acid tails (hates water). When mixed with water, these clever molecules automatically arrange themselves with heads facing outward and tails tucked safely inside.
Intrinsic proteins are embedded right through the membrane, whilst extrinsic proteins sit on the surface like decorations. The positioning of these proteins depends entirely on their hydrophilic and hydrophobic regions - they naturally find their perfect spot.
It's called the "fluid mosaic" model because phospholipids and proteins can move around freely (fluid), creating a scattered, tile-like pattern (mosaic). Cholesterol molecules squeeze between phospholipids, acting like tiny regulators that keep the membrane at just the right consistency.
Key Point The membrane's structure is self-organising - molecules arrange themselves based on whether they love or hate water!
Cholesterol is your membrane's temperature regulator and bodyguard. It prevents phospholipids from packing too tightly (stops freezing) and provides stability at high temperatures. Think of it as the membrane's personal trainer, keeping everything flexible yet strong.
Glycolipids and glycoproteins act like the cell's reception desk. They bind to specific substances like hormones and neurotransmitters, and work as cell markers for antigens. These are your cell's way of communicating with the outside world.
Transport proteins are the membrane's delivery service. Channel proteins create specific tunnels for ions (used in facilitated diffusion), whilst carrier proteins actually change shape to push larger molecules through using ATP in active transport.
Exam Tip Remember that channel proteins are for small ions, carrier proteins are for bigger molecules and require energy!
When temperatures rise, your membrane structure changes dramatically. High temperatures cause phospholipids to vibrate more due to increased kinetic energy, creating gaps and making the membrane more fluid. Channel and carrier proteins can also denature, losing their specific shapes.
For exam questions about active transport evidence, look for two key clues. If dye leaks out at high temperatures, carrier proteins have denatured. If dye constantly moves into cells against the concentration gradient, that's definitely active transport in action.
To improve any membrane experiment, focus on accuracy (take more readings at smaller temperature intervals) and reliability (repeat experiments for means and to spot anomalies). These simple improvements can transform your practical write-ups.
Success Strategy Practice describing structural changes without mentioning function - examiners love this distinction and it's an easy way to gain marks!
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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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential concepts of plant and animal transport systems, including xylem and phloem functions, blood vessel structures, and the role of stem cells in growth and repair. This summary covers key topics such as cellular respiration, the nervous system, and the structure and function of cells, making it a valuable resource for SQA National 5 Biology students.
BiologyExplore the essential functions and structures of cell membranes, including the fluid mosaic model, phospholipid bilayer, and the role of membrane proteins. This summary covers how membranes regulate substance movement, compartmentalize cellular functions, and facilitate communication within and outside the cell.
BiologyExplore key concepts of cell structure and function in this comprehensive glossary. Understand the roles of organelles, transport mechanisms, and cellular processes essential for A-level biology. Ideal for students seeking clarity on cell anatomy, membrane transport, and the differences between eukaryotic and prokaryotic cells.
BiologyExplore the structure of biological membranes and the various transport mechanisms including simple diffusion, facilitated diffusion, and active transport. This summary covers key concepts such as glycolipids, glycoproteins, and the phospholipid bilayer, essential for A-Level Biology students across all exam boards (OCR, Edexcel, AQA).
BiologyExplore key concepts in cell biology, including DNA structure, protein synthesis, cellular respiration, and genetic engineering. This summary covers essential processes such as glycolysis, fermentation, and enzyme functions, providing a comprehensive overview for students studying cellular structures and functions. Ideal for Nat 5 Biology revision.
BiologyExplore key concepts in NAT5 Biology with this comprehensive summary covering proteins, enzymes, DNA structure, cellular respiration, and genetic engineering. Understand the roles of organelles, protein synthesis, and transport mechanisms like diffusion and osmosis. Ideal for exam preparation and quick revision.
BiologyApp Store
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
Kadiok
@kadiokee
Cell membranes aren't just simple barriers - they're complex, dynamic structures that control everything entering and leaving your cells. Understanding the fluid mosaic model and how temperature affects membrane structure is crucial for your A-level Biology exams.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of cell membranes as a flexible sandwich made primarily of phospholipids arranged in a bilayer. Each phospholipid has a hydrophilic phosphate head (loves water) and hydrophobic fatty acid tails (hates water). When mixed with water, these clever molecules automatically arrange themselves with heads facing outward and tails tucked safely inside.
Intrinsic proteins are embedded right through the membrane, whilst extrinsic proteins sit on the surface like decorations. The positioning of these proteins depends entirely on their hydrophilic and hydrophobic regions - they naturally find their perfect spot.
It's called the "fluid mosaic" model because phospholipids and proteins can move around freely (fluid), creating a scattered, tile-like pattern (mosaic). Cholesterol molecules squeeze between phospholipids, acting like tiny regulators that keep the membrane at just the right consistency.
Key Point: The membrane's structure is self-organising - molecules arrange themselves based on whether they love or hate water!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Cholesterol is your membrane's temperature regulator and bodyguard. It prevents phospholipids from packing too tightly (stops freezing) and provides stability at high temperatures. Think of it as the membrane's personal trainer, keeping everything flexible yet strong.
Glycolipids and glycoproteins act like the cell's reception desk. They bind to specific substances like hormones and neurotransmitters, and work as cell markers for antigens. These are your cell's way of communicating with the outside world.
Transport proteins are the membrane's delivery service. Channel proteins create specific tunnels for ions (used in facilitated diffusion), whilst carrier proteins actually change shape to push larger molecules through using ATP in active transport.
Exam Tip: Remember that channel proteins are for small ions, carrier proteins are for bigger molecules and require energy!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When temperatures rise, your membrane structure changes dramatically. High temperatures cause phospholipids to vibrate more due to increased kinetic energy, creating gaps and making the membrane more fluid. Channel and carrier proteins can also denature, losing their specific shapes.
For exam questions about active transport evidence, look for two key clues. If dye leaks out at high temperatures, carrier proteins have denatured. If dye constantly moves into cells against the concentration gradient, that's definitely active transport in action.
To improve any membrane experiment, focus on accuracy (take more readings at smaller temperature intervals) and reliability (repeat experiments for means and to spot anomalies). These simple improvements can transform your practical write-ups.
Success Strategy: Practice describing structural changes without mentioning function - examiners love this distinction and it's an easy way to gain marks!
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.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential concepts of plant and animal transport systems, including xylem and phloem functions, blood vessel structures, and the role of stem cells in growth and repair. This summary covers key topics such as cellular respiration, the nervous system, and the structure and function of cells, making it a valuable resource for SQA National 5 Biology students.
BiologyExplore the essential functions and structures of cell membranes, including the fluid mosaic model, phospholipid bilayer, and the role of membrane proteins. This summary covers how membranes regulate substance movement, compartmentalize cellular functions, and facilitate communication within and outside the cell.
BiologyExplore key concepts of cell structure and function in this comprehensive glossary. Understand the roles of organelles, transport mechanisms, and cellular processes essential for A-level biology. Ideal for students seeking clarity on cell anatomy, membrane transport, and the differences between eukaryotic and prokaryotic cells.
BiologyExplore the structure of biological membranes and the various transport mechanisms including simple diffusion, facilitated diffusion, and active transport. This summary covers key concepts such as glycolipids, glycoproteins, and the phospholipid bilayer, essential for A-Level Biology students across all exam boards (OCR, Edexcel, AQA).
BiologyExplore key concepts in cell biology, including DNA structure, protein synthesis, cellular respiration, and genetic engineering. This summary covers essential processes such as glycolysis, fermentation, and enzyme functions, providing a comprehensive overview for students studying cellular structures and functions. Ideal for Nat 5 Biology revision.
BiologyExplore key concepts in NAT5 Biology with this comprehensive summary covering proteins, enzymes, DNA structure, cellular respiration, and genetic engineering. Understand the roles of organelles, protein synthesis, and transport mechanisms like diffusion and osmosis. Ideal for exam preparation and quick revision.
BiologyApp Store
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
Sociology