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
7 Dec 2025
59
2 pages
DA @dharina21
Every living thing is made up of cells - they're literally the building blocks of life! Understanding how... Show more
Think of a cell as a bustling factory where countless processes happen simultaneously to keep you alive. Each cell has a specific job, whether it's carrying oxygen in your blood or helping you digest food.
The cell membrane acts like a selective bouncer at a club - it decides what gets in and what stays out. This selectively permeable barrier separates everything inside the cell (intracellular) from the outside environment (extracellular), maintaining perfect control over the cell's internal conditions.
Inside every cell, you'll find two main regions the cytoplasm and the nucleus (the control centre). The cytoplasm houses amazing structures called organelles - think of them as specialised departments in our cellular factory.
Key organelles include the endoplasmic reticulum (ER), which comes in two types rough ER (covered in ribosomes for making proteins) and smooth ER. You'll also find the Golgi apparatus for storage, mitochondria (the powerhouses making ATP energy), and lysosomes containing digestive enzymes to break down waste.
Quick Tip Remember mitochondria as the "powerhouse of the cell" - this fact appears in virtually every biology exam!
The nucleus is like mission control, containing all the instructions needed to run your entire body. Inside, you'll find DNA organised as chromatin (loose threads) or chromosomes (tightly packed bundles during cell division).
DNA forms a double helix structure with four bases Guanine, Cytosine, Adenine, and Thymine. The sequence of these bases creates genes - specific instructions for making proteins. Since DNA is too large to leave the nucleus, it creates a messenger called RNA to carry instructions to the ribosomes.
This RNA acts like a delivery service, bringing protein-making instructions from the nucleus to ribosomes in the cytoplasm. The ribosomes then build chains of amino acids to create specific proteins - this is how your body makes everything from hair and nails to enzymes.
Cell division happens through two processes Mitosis (creating two identical cells for growth and repair) and Meiosis (creating reproductive cells called gametes). Most human cells contain 46 chromosomes (23 pairs, called the diploid number), but gametes only have 23 chromosomes (the haploid number).
Remember DNA → RNA → Protein is the central dogma of biology - this sequence explains how genetic information becomes functional proteins in your body.
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 processes of cell differentiation, the cell cycle, mitosis, and meiosis. Understand the roles of stem cells, their potency, and the significance of specialized cells like erythrocytes and neutrophils. This summary also addresses ethical concerns surrounding stem cell use and highlights the organization of cells into tissues and organs.
BiologyExplore the detailed stages of mitosis, including Prophase, Metaphase, Anaphase, and Telophase. This summary highlights key events such as chromatin condensation, spindle apparatus formation, and cytokinesis, essential for A Level Biology students. Understand the cell cycle phases and their significance in cell division.
BiologyExplore the essential processes of photosynthesis, including the role of chlorophyll, light-dependent reactions, and factors affecting plant growth. This summary covers the conversion of carbon dioxide and water into glucose, the importance of light, and adaptations of leaves for optimal photosynthesis. Ideal for GCSE Biology students seeking to understand plant productivity and the significance of photosynthesis in ecosystems.
BiologyExplore the detailed stages of mitosis, including early prophase, metaphase, anaphase, and telophase. Understand the role of chromosomes, chromatids, and centrioles in cell division. This summary provides a clear overview of the mitotic process, essential for biology students.
BiologyExplore the intricacies of the cell cycle, including interphase stages (G1, S, G2), the role of checkpoints, and the significance of G0 phase. This summary provides insights into cell growth, division, and regulation mechanisms essential for maintaining cellular integrity.
BiologyExplore the stages of mitosis in detail, including interphase, prophase, metaphase, anaphase, and telophase. This concise summary highlights the key processes involved in cell division, essential for GCSE Edexcel and AQA students. Understand how mitosis contributes to growth and cell replacement, and use the PMAT acronym to remember the sequence of events.
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
DA
@dharina21
Every living thing is made up of cells - they're literally the building blocks of life! Understanding how cells work is crucial for grasping everything from how your body grows and repairs itself to how genetic information gets passed down... 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 bustling factory where countless processes happen simultaneously to keep you alive. Each cell has a specific job, whether it's carrying oxygen in your blood or helping you digest food.
The cell membrane acts like a selective bouncer at a club - it decides what gets in and what stays out. This selectively permeable barrier separates everything inside the cell (intracellular) from the outside environment (extracellular), maintaining perfect control over the cell's internal conditions.
Inside every cell, you'll find two main regions: the cytoplasm and the nucleus (the control centre). The cytoplasm houses amazing structures called organelles - think of them as specialised departments in our cellular factory.
Key organelles include the endoplasmic reticulum (ER), which comes in two types: rough ER (covered in ribosomes for making proteins) and smooth ER. You'll also find the Golgi apparatus for storage, mitochondria (the powerhouses making ATP energy), and lysosomes containing digestive enzymes to break down waste.
Quick Tip: Remember mitochondria as the "powerhouse of the cell" - this fact appears in virtually every biology exam!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The nucleus is like mission control, containing all the instructions needed to run your entire body. Inside, you'll find DNA organised as chromatin (loose threads) or chromosomes (tightly packed bundles during cell division).
DNA forms a double helix structure with four bases: Guanine, Cytosine, Adenine, and Thymine. The sequence of these bases creates genes - specific instructions for making proteins. Since DNA is too large to leave the nucleus, it creates a messenger called RNA to carry instructions to the ribosomes.
This RNA acts like a delivery service, bringing protein-making instructions from the nucleus to ribosomes in the cytoplasm. The ribosomes then build chains of amino acids to create specific proteins - this is how your body makes everything from hair and nails to enzymes.
Cell division happens through two processes: Mitosis (creating two identical cells for growth and repair) and Meiosis (creating reproductive cells called gametes). Most human cells contain 46 chromosomes (23 pairs, called the diploid number), but gametes only have 23 chromosomes (the haploid number).
Remember: DNA → RNA → Protein is the central dogma of biology - this sequence explains how genetic information becomes functional proteins in your body.
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 processes of cell differentiation, the cell cycle, mitosis, and meiosis. Understand the roles of stem cells, their potency, and the significance of specialized cells like erythrocytes and neutrophils. This summary also addresses ethical concerns surrounding stem cell use and highlights the organization of cells into tissues and organs.
BiologyExplore the detailed stages of mitosis, including Prophase, Metaphase, Anaphase, and Telophase. This summary highlights key events such as chromatin condensation, spindle apparatus formation, and cytokinesis, essential for A Level Biology students. Understand the cell cycle phases and their significance in cell division.
BiologyExplore the essential processes of photosynthesis, including the role of chlorophyll, light-dependent reactions, and factors affecting plant growth. This summary covers the conversion of carbon dioxide and water into glucose, the importance of light, and adaptations of leaves for optimal photosynthesis. Ideal for GCSE Biology students seeking to understand plant productivity and the significance of photosynthesis in ecosystems.
BiologyExplore the detailed stages of mitosis, including early prophase, metaphase, anaphase, and telophase. Understand the role of chromosomes, chromatids, and centrioles in cell division. This summary provides a clear overview of the mitotic process, essential for biology students.
BiologyExplore the intricacies of the cell cycle, including interphase stages (G1, S, G2), the role of checkpoints, and the significance of G0 phase. This summary provides insights into cell growth, division, and regulation mechanisms essential for maintaining cellular integrity.
BiologyExplore the stages of mitosis in detail, including interphase, prophase, metaphase, anaphase, and telophase. This concise summary highlights the key processes involved in cell division, essential for GCSE Edexcel and AQA students. Understand how mitosis contributes to growth and cell replacement, and use the PMAT acronym to remember the sequence of events.
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