Maths
Chemistry
Biology
English Language
History
Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
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
World war one
Britain: 1509 -1745
Show all topics
Biology
3 Dec 2025
321
4 pages
eva marshall @evamarshall_
Every living thing around you is made up of tiny building blocks called cells - from the skin... Show more
Think of a cell as a tiny factory where each part has a specific job to keep everything running smoothly. The cell membrane acts like a security guard, deciding what can enter and leave the cell - it's semi-permeable, meaning it's picky about what gets through.
Inside, the cytoplasm is where all the action happens - it's the liquid space where chemical reactions take place. The nucleus is like the cell's control centre, storing all your genetic information on chromosomes that you inherited from your parents.
Mitochondria are the powerhouses that release energy through aerobic respiration - basically, they keep your cells energised! Plant cells have extra bits a cell wall made of cellulose for protection, chloroplasts containing chlorophyll to trap light for photosynthesis, and a large vacuole for support.
Quick Tip Remember that plant cells have everything animal cells have, plus three extras cell wall, chloroplasts, and a large vacuole!
Cells are just the beginning of an amazing organisational system that builds up to create you! When similar cells group together to do the same job, they form tissues - like cardiac muscle tissue in your heart.
Different tissues then team up to create organs with specific functions. Your heart, for example, combines muscle tissue, nerve tissue, and blood vessels to pump blood around your body.
Organ systems form when multiple organs work together - your circulatory system includes your heart, blood vessels, and blood all cooperating. Finally, all your organ systems work together to create a complete organism - that's you!
Remember It's like Russian dolls - cells fit into tissues, tissues into organs, organs into systems, and systems make you!
Diffusion is simply the movement of molecules from where there's loads of them to where there's fewer - like how perfume spreads across a room. This process is crucial for getting oxygen, water, and glucose into cells, and removing waste like CO₂.
Three main factors affect how fast diffusion happens. Temperature speeds things up because particles have more kinetic energy to move around. A larger surface area of the cell membrane means more particles can cross at once.
The concentration gradient is probably the most important factor - the bigger the difference between high and low concentration areas, the faster diffusion occurs. It's like water flowing down a steep hill versus a gentle slope.
Resolution in microscopy refers to seeing two separate points as distinct after magnification - basically, how clear and detailed your view is when studying cells.
Pro Tip Think of diffusion like people leaving a crowded concert - they naturally spread out from the packed venue to less crowded areas!
Animal cells contain the basic kit cell membrane, mitochondria, cytoplasm, nucleus, and nuclear membrane. They're like the standard model that does all the essential life functions.
Plant cells have everything animal cells do, plus their special extras for plant life. The cell wall provides extra protection, chloroplasts enable photosynthesis, and the large vacuole helps maintain structure and support.
Bacterial cells are the rebels - they're much simpler with a non-cellulose cell wall, cytoplasm, and genetic material floating freely as loops of DNA rather than organised in a nucleus. They also have plasmids, which are small rings of extra DNA.
Stem cells are the ultimate multitaskers - they can divide and differentiate into specialised cells. Adult stem cells (found in bone marrow) are limited in what they can become, whilst embryonic stem cells can potentially become any type of cell.
Key Point The main difference between these cell types is complexity - bacterial cells are simplest, animal cells are more complex, and plant cells are the most complex with extra features!
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.
10
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential role of Adenosine Triphosphate (ATP) in cellular respiration and photosynthesis. This summary covers ATP hydrolysis, its function as an immediate energy source, and its importance in various cellular processes such as muscle contraction and active transport. Understand why ATP is not an energy storage molecule and how it is continuously synthesized to meet cellular demands.
BiologyExplore the key differences between eukaryotic and prokaryotic cells, including their structures and functions. This summary covers essential components such as the nucleus, mitochondria, chloroplasts, and more, providing a clear understanding of cellular biology. Ideal for students studying cellular structure and functions.
BiologyExplore the essential components of plant and animal cells, including the cell wall, nucleus, cytoplasm, and mitochondria. This summary provides a clear overview of cell structures, their functions, and the differences between plant and animal cells, perfect for Year 7 revision. Ideal for students preparing for exams.
Biologyscience biology revision cards
BiologyExplore the key sub-cellular structures of plant cells, including the cell membrane, cell wall, vacuole, cytoplasm, chloroplasts, and nucleus. Understand their functions such as support, protection, storage, and photosynthesis in this informative summary.
BiologyExplore the essential sub-cellular structures including the cell membrane, cytoplasm, nucleus, cell wall, chloroplasts, and permanent vacuole. This summary highlights their functions and locations in different cell types, providing a clear understanding of cellular organization. Ideal for biology students studying cell structure and function.
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
eva marshall
@evamarshall_
Every living thing around you is made up of tiny building blocks called cells - from the skin on your hands to the leaves on trees. Understanding how cells work and organise themselves is key to grasping how all life... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of a cell as a tiny factory where each part has a specific job to keep everything running smoothly. The cell membrane acts like a security guard, deciding what can enter and leave the cell - it's semi-permeable, meaning it's picky about what gets through.
Inside, the cytoplasm is where all the action happens - it's the liquid space where chemical reactions take place. The nucleus is like the cell's control centre, storing all your genetic information on chromosomes that you inherited from your parents.
Mitochondria are the powerhouses that release energy through aerobic respiration - basically, they keep your cells energised! Plant cells have extra bits: a cell wall made of cellulose for protection, chloroplasts containing chlorophyll to trap light for photosynthesis, and a large vacuole for support.
Quick Tip: Remember that plant cells have everything animal cells have, plus three extras: cell wall, chloroplasts, and a large vacuole!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Cells are just the beginning of an amazing organisational system that builds up to create you! When similar cells group together to do the same job, they form tissues - like cardiac muscle tissue in your heart.
Different tissues then team up to create organs with specific functions. Your heart, for example, combines muscle tissue, nerve tissue, and blood vessels to pump blood around your body.
Organ systems form when multiple organs work together - your circulatory system includes your heart, blood vessels, and blood all cooperating. Finally, all your organ systems work together to create a complete organism - that's you!
Remember: It's like Russian dolls - cells fit into tissues, tissues into organs, organs into systems, and systems make you!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Diffusion is simply the movement of molecules from where there's loads of them to where there's fewer - like how perfume spreads across a room. This process is crucial for getting oxygen, water, and glucose into cells, and removing waste like CO₂.
Three main factors affect how fast diffusion happens. Temperature speeds things up because particles have more kinetic energy to move around. A larger surface area of the cell membrane means more particles can cross at once.
The concentration gradient is probably the most important factor - the bigger the difference between high and low concentration areas, the faster diffusion occurs. It's like water flowing down a steep hill versus a gentle slope.
Resolution in microscopy refers to seeing two separate points as distinct after magnification - basically, how clear and detailed your view is when studying cells.
Pro Tip: Think of diffusion like people leaving a crowded concert - they naturally spread out from the packed venue to less crowded areas!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Animal cells contain the basic kit: cell membrane, mitochondria, cytoplasm, nucleus, and nuclear membrane. They're like the standard model that does all the essential life functions.
Plant cells have everything animal cells do, plus their special extras for plant life. The cell wall provides extra protection, chloroplasts enable photosynthesis, and the large vacuole helps maintain structure and support.
Bacterial cells are the rebels - they're much simpler with a non-cellulose cell wall, cytoplasm, and genetic material floating freely as loops of DNA rather than organised in a nucleus. They also have plasmids, which are small rings of extra DNA.
Stem cells are the ultimate multitaskers - they can divide and differentiate into specialised cells. Adult stem cells (found in bone marrow) are limited in what they can become, whilst embryonic stem cells can potentially become any type of cell.
Key Point: The main difference between these cell types is complexity - bacterial cells are simplest, animal cells are more complex, and plant cells are the most complex with extra features!
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.
10
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential role of Adenosine Triphosphate (ATP) in cellular respiration and photosynthesis. This summary covers ATP hydrolysis, its function as an immediate energy source, and its importance in various cellular processes such as muscle contraction and active transport. Understand why ATP is not an energy storage molecule and how it is continuously synthesized to meet cellular demands.
BiologyExplore the key differences between eukaryotic and prokaryotic cells, including their structures and functions. This summary covers essential components such as the nucleus, mitochondria, chloroplasts, and more, providing a clear understanding of cellular biology. Ideal for students studying cellular structure and functions.
BiologyExplore the essential components of plant and animal cells, including the cell wall, nucleus, cytoplasm, and mitochondria. This summary provides a clear overview of cell structures, their functions, and the differences between plant and animal cells, perfect for Year 7 revision. Ideal for students preparing for exams.
Biologyscience biology revision cards
BiologyExplore the key sub-cellular structures of plant cells, including the cell membrane, cell wall, vacuole, cytoplasm, chloroplasts, and nucleus. Understand their functions such as support, protection, storage, and photosynthesis in this informative summary.
BiologyExplore the essential sub-cellular structures including the cell membrane, cytoplasm, nucleus, cell wall, chloroplasts, and permanent vacuole. This summary highlights their functions and locations in different cell types, providing a clear understanding of cellular organization. Ideal for biology students studying cell structure and function.
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