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
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
1 Dec 2025
121
4 pages
Gracie B @gracieb_l513o
Cells are the building blocks of all life, from tiny bacteria to complex humans. Understanding how cells work,... Show more
Ever wondered what makes you different from a bacterium? It's all about whether your cells have a nucleus or not. Eukaryotic cells (like yours and plant cells) keep their genetic material safely tucked inside a nucleus, whilst prokaryotic cells (bacteria) let their DNA float freely around.
Each part of a cell has a specific job. The cytoplasm is where chemical reactions happen, mitochondria are your cellular powerhouses for respiration, and ribosomes are protein factories. Plant cells get extra features like chloroplasts for photosynthesis and a cell wall for strength.
Cell division happens through mitosis, where one cell splits into two identical copies. Stem cells are special because they haven't decided what to become yet - they can turn into any type of cell your body needs.
Key Point Specialised cells like sperm, nerve cells, and muscle cells are perfectly designed for their specific jobs through a process called differentiation.
Your body is brilliantly organised - it's like a company with different departments working together. Cells group together to form tissues, tissues combine into organs, and organs work together as organ systems.
Take your digestive system - it's a perfect example of teamwork. Your mouth produces saliva containing amylase enzymes that break down starch, your stomach churns food with digestive juices, and your small intestine handles the final digestion and absorption.
Your circulatory system is equally impressive. Arteries carry blood away from your heart under high pressure with thick walls, whilst veins bring blood back with thinner walls and handy valves to prevent backflow. Tiny capillaries connect them, allowing gas exchange in your lungs' alveoli.
Enzymes are biological catalysts that speed up reactions - they're very fussy about temperature and pH levels. In plants, transpiration moves water from roots to leaves, whilst translocation carries sugars around the plant.
Key Point Every level of organisation - from cells to organ systems - has a specific function that contributes to keeping you alive and healthy.
Pathogens are microorganisms that want to make you ill, and they're surprisingly sneaky about it. They spread through direct contact, contaminated water, air droplets, or vectors like mosquitoes carrying malaria.
Different pathogens cause different problems. Viruses like measles and HIV hijack your cells to reproduce rapidly. Bacteria produce toxins that damage your tissues - think salmonella food poisoning. Fungi cause issues like rose black spot in plants, whilst protists give us diseases like malaria.
Fortunately, your body has an amazing defence system. Your skin acts as a barrier, your nose hairs trap particles, and your stomach acid kills unwanted guests. Your immune system then produces antibodies and antitoxins to fight specific threats.
Vaccination is like giving your immune system a practice run with dead or weakened pathogens. Antibiotics kill bacteria (but not viruses!), though antibiotic resistance is becoming a serious problem as bacteria evolve to survive our medicines.
Key Point Your immune system has memory - once it's fought a pathogen, it remembers how to defeat it quickly if it returns.
Photosynthesis is probably the most important process on Earth - it's how plants turn sunlight, carbon dioxide, and water into glucose and oxygen. The equation is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Limiting factors can slow down photosynthesis - mainly light intensity, temperature, and CO₂ concentration. If any one of these is in short supply, it becomes the bottleneck that limits the whole process.
Respiration is photosynthesis in reverse - it breaks down glucose to release energy. Aerobic respiration needs oxygen and produces lots of ATP energy, whilst anaerobic respiration happens without oxygen but produces less energy (and lactic acid in your muscles during intense exercise).
When you exercise hard, your heart pumps faster and you breathe deeper to supply oxygen and remove carbon dioxide. Oxygen debt occurs when your muscles produce lactic acid faster than you can supply oxygen - that's why you keep breathing heavily after stopping exercise.
Key Point Photosynthesis and respiration are complementary processes - plants and animals depend on each other for the gases they need.
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
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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
Gracie B
@gracieb_l513o
Cells are the building blocks of all life, from tiny bacteria to complex humans. Understanding how cells work, reproduce, and organise themselves into tissues and organs is fundamental to biology. You'll also explore how plants make food through photosynthesis and... Show more
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Improve your grades
Join milions of students
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Ever wondered what makes you different from a bacterium? It's all about whether your cells have a nucleus or not. Eukaryotic cells (like yours and plant cells) keep their genetic material safely tucked inside a nucleus, whilst prokaryotic cells (bacteria) let their DNA float freely around.
Each part of a cell has a specific job. The cytoplasm is where chemical reactions happen, mitochondria are your cellular powerhouses for respiration, and ribosomes are protein factories. Plant cells get extra features like chloroplasts for photosynthesis and a cell wall for strength.
Cell division happens through mitosis, where one cell splits into two identical copies. Stem cells are special because they haven't decided what to become yet - they can turn into any type of cell your body needs.
Key Point: Specialised cells like sperm, nerve cells, and muscle cells are perfectly designed for their specific jobs through a process called differentiation.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your body is brilliantly organised - it's like a company with different departments working together. Cells group together to form tissues, tissues combine into organs, and organs work together as organ systems.
Take your digestive system - it's a perfect example of teamwork. Your mouth produces saliva containing amylase enzymes that break down starch, your stomach churns food with digestive juices, and your small intestine handles the final digestion and absorption.
Your circulatory system is equally impressive. Arteries carry blood away from your heart under high pressure with thick walls, whilst veins bring blood back with thinner walls and handy valves to prevent backflow. Tiny capillaries connect them, allowing gas exchange in your lungs' alveoli.
Enzymes are biological catalysts that speed up reactions - they're very fussy about temperature and pH levels. In plants, transpiration moves water from roots to leaves, whilst translocation carries sugars around the plant.
Key Point: Every level of organisation - from cells to organ systems - has a specific function that contributes to keeping you alive and healthy.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Pathogens are microorganisms that want to make you ill, and they're surprisingly sneaky about it. They spread through direct contact, contaminated water, air droplets, or vectors like mosquitoes carrying malaria.
Different pathogens cause different problems. Viruses like measles and HIV hijack your cells to reproduce rapidly. Bacteria produce toxins that damage your tissues - think salmonella food poisoning. Fungi cause issues like rose black spot in plants, whilst protists give us diseases like malaria.
Fortunately, your body has an amazing defence system. Your skin acts as a barrier, your nose hairs trap particles, and your stomach acid kills unwanted guests. Your immune system then produces antibodies and antitoxins to fight specific threats.
Vaccination is like giving your immune system a practice run with dead or weakened pathogens. Antibiotics kill bacteria (but not viruses!), though antibiotic resistance is becoming a serious problem as bacteria evolve to survive our medicines.
Key Point: Your immune system has memory - once it's fought a pathogen, it remembers how to defeat it quickly if it returns.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Photosynthesis is probably the most important process on Earth - it's how plants turn sunlight, carbon dioxide, and water into glucose and oxygen. The equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Limiting factors can slow down photosynthesis - mainly light intensity, temperature, and CO₂ concentration. If any one of these is in short supply, it becomes the bottleneck that limits the whole process.
Respiration is photosynthesis in reverse - it breaks down glucose to release energy. Aerobic respiration needs oxygen and produces lots of ATP energy, whilst anaerobic respiration happens without oxygen but produces less energy (and lactic acid in your muscles during intense exercise).
When you exercise hard, your heart pumps faster and you breathe deeper to supply oxygen and remove carbon dioxide. Oxygen debt occurs when your muscles produce lactic acid faster than you can supply oxygen - that's why you keep breathing heavily after stopping exercise.
Key Point: Photosynthesis and respiration are complementary processes - plants and animals depend on each other for the gases they need.
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.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
App 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