Subjects
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
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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
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Biology
10 Dec 2025
86
1 page
Every cell in your body is like a bustling city, packed with tiny structures called organelles that keep... Show more
Think of organelles as the specialized departments in a cell's factory. Each one has a specific job that keeps the cell alive and functioning properly.
The cell-surface membrane acts like a selective security gate around the cell. It's made of a phospholipid bilayer with proteins, cholesterol, and special recognition molecules called glycoproteins and glycolipids. This structure is known as the fluid-mosaic model because it's flexible and contains various types of molecules that can move around.
The nucleus is basically the cell's control center, surrounded by a nuclear envelope with tiny doorways called nuclear pores. Inside, you'll find chromosomes (your DNA) and the nucleolus, which churns out ribosomes like a factory producing protein-making machines.
Mitochondria are the cell's powerhouses, featuring a double membrane with folded inner sections called cristae. They're where aerobic respiration happens, converting glucose into ATP - the cell's energy currency. Meanwhile, chloroplasts (found only in plants) have a similar double membrane structure but contain thylakoids packed with chlorophyll for photosynthesis.
๐ก Quick Tip Remember that mitochondria and chloroplasts both have double membranes because they likely evolved from ancient bacteria!
The Golgi apparatus works like a post office, modifying and packaging proteins in stacked membranes called cisternae. Lysosomes are special Golgi vesicles filled with digestive enzymes that break down waste. Ribosomes are the actual protein factories, whilst the endoplasmic reticulum provides highways for transport - the RER (with ribosomes attached) handles proteins, and the SER deals with lipids.
Plant cells get extra support from their cell wall made of cellulose, plus a large cell vacuole surrounded by a tonoplast membrane for storage and structural support. The cytoskeleton runs throughout all cells like scaffolding, providing strength and helping organelles move around.
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 โ all at your fingertips.
1
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ 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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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
Every cell in your body is like a bustling city, packed with tiny structures called organelles that keep everything running smoothly. Understanding what each organelle does is crucial for grasping how life works at the most basic level - and... Show more
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Think of organelles as the specialized departments in a cell's factory. Each one has a specific job that keeps the cell alive and functioning properly.
The cell-surface membrane acts like a selective security gate around the cell. It's made of a phospholipid bilayer with proteins, cholesterol, and special recognition molecules called glycoproteins and glycolipids. This structure is known as the fluid-mosaic model because it's flexible and contains various types of molecules that can move around.
The nucleus is basically the cell's control center, surrounded by a nuclear envelope with tiny doorways called nuclear pores. Inside, you'll find chromosomes (your DNA) and the nucleolus, which churns out ribosomes like a factory producing protein-making machines.
Mitochondria are the cell's powerhouses, featuring a double membrane with folded inner sections called cristae. They're where aerobic respiration happens, converting glucose into ATP - the cell's energy currency. Meanwhile, chloroplasts (found only in plants) have a similar double membrane structure but contain thylakoids packed with chlorophyll for photosynthesis.
๐ก Quick Tip: Remember that mitochondria and chloroplasts both have double membranes because they likely evolved from ancient bacteria!
The Golgi apparatus works like a post office, modifying and packaging proteins in stacked membranes called cisternae. Lysosomes are special Golgi vesicles filled with digestive enzymes that break down waste. Ribosomes are the actual protein factories, whilst the endoplasmic reticulum provides highways for transport - the RER (with ribosomes attached) handles proteins, and the SER deals with lipids.
Plant cells get extra support from their cell wall made of cellulose, plus a large cell vacuole surrounded by a tonoplast membrane for storage and structural support. The cytoskeleton runs throughout all cells like scaffolding, providing strength and helping organelles move around.
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 โ all at your fingertips.
1
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ 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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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
Combined Science
Sociology