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Updated Mar 23, 2026
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Cell Structure and Division in AQA Biology
libby griffiths
@libbygriffiths_azle
1 / 4
Cell Structures and Organisation
Think of your cells as bustling cities - each organelle has a specific job that keeps everything running smoothly. The nucleus acts like city hall, containing your DNA and controlling protein production. Meanwhile, mitochondria work as power stations, creating ATP energy exactly where your cells need it most.
Your cellular transport system is equally impressive. The Golgi apparatus functions like a post office, packaging and labelling proteins before shipping them to their destinations via transport vesicles. Lysosomes serve as the cleanup crew, using digestive enzymes to destroy unwanted materials or invading cells when necessary.
Eukaryotic cells (like yours) are far more complex than prokaryotic cells (like bacteria). Whilst your cells have membrane-bound organelles and a proper nucleus, bacterial cells keep their circular DNA floating freely in the cytoplasm. They reproduce through binary fission, simply copying their DNA and splitting in half.
Quick Check: Plant cells have everything animal cells do, plus chloroplasts for photosynthesis, a rigid cell wall, and a large vacuole for support and storage.
Viruses and Microscopy Techniques
Viruses aren't actually alive - they're basically genetic pirates that hijack your cells to reproduce. These acellular particles consist of nucleic acid wrapped in a protein coat called a capsid. They can't divide on their own, so they inject their DNA or RNA into host cells and force them to make viral copies.
Different viruses attack different cells because they need specific receptor proteins to attach. This is why some viruses only target particular cell types whilst others can infect multiple tissues.
To study these tiny structures, scientists use powerful electron microscopes. TEM (Transmission Electron Microscopy) shoots electrons through ultra-thin specimens for detailed internal views, whilst SEM (Scanning Electron Microscopy) bounces electrons off surfaces to create 3D images.
Cell fractionation lets researchers separate organelles by density using ultracentrifugation. After breaking cells open in a blender, they spin the mixture at increasing speeds - heavy nuclei settle first, then chloroplasts, mitochondria, and finally lightweight ribosomes.
Remember: Electron microscopes can only examine dead specimens in a vacuum, but they reveal details impossible to see with light microscopes.
Mitosis and Cell Division Control
Your body performs millions of mitosis events daily for growth and repair, creating two identical daughter cells from one parent cell. The process follows four main stages after interphase (when DNA replicates and organelles duplicate).
During prophase, chromosomes condense and the nuclear envelope dissolves. In metaphase, chromosomes line up centrally and attach to spindle fibres. Anaphase sees chromatids separate and move to opposite cell poles, whilst telophase reforms two nuclei as chromosomes uncoil.
The cell cycle includes growth phases (G1 and G2) surrounding DNA replication (S phase) before mitosis begins. Growth factors and specific genes carefully control this timing - when this control breaks down, cancer develops.
Malignant tumours grow rapidly and spread, making them more dangerous than slower-growing benign tumours. Cancer treatments often target dividing cells by preventing DNA replication or disrupting spindle formation, though this can unfortunately affect healthy cells too.
Key Point: Cancer occurs when normal cell division controls fail, allowing uncontrolled growth and potentially life-threatening tumour formation.
Stem Cells and Medical Applications
Stem cells are your body's master cells - undifferentiated and capable of becoming specialised cell types through a process called differentiation. You've got two main types: embryonic stem cells can become any cell type, whilst adult stem cells have more limited options.
Embryonic stem cells from 3-5 day old embryos offer incredible medical potential since they're pluripotent (can become anything). Adult stem cells from places like bone marrow are more restricted but already help treat blood disorders through transplants.
Therapeutic cloning creates embryos with identical genetic material to patients, potentially solving tissue rejection problems. However, risks include viral contamination during laboratory growth and the possibility of transmitting infections.
The biggest hurdles aren't scientific but ethical. Many people have religious or moral objections to destroying embryos for stem cells, viewing them as potential human life. Fortunately, researchers can often use leftover IVF embryos or collect stem cells from umbilical cord blood after birth - a completely safe, non-invasive alternative.
Looking Ahead: Stem cell therapy could revolutionise medicine, potentially treating everything from spinal injuries to heart disease once we overcome current limitations.
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Stefan S
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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.
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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
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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
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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 Knowunity AI. 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 Knowunity AI. 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
Cell Structure and Division in AQA Biology
libby griffiths
@libbygriffiths_azle
Your cells are like incredibly organised factories, each with specialised departments working together to keep you alive. Understanding how these cellular structures function, divide, and develop will help you grasp everything from why you grow taller to how diseases like... Show more
Cell Structures and Organisation
Think of your cells as bustling cities - each organelle has a specific job that keeps everything running smoothly. The nucleus acts like city hall, containing your DNA and controlling protein production. Meanwhile, mitochondria work as power stations, creating ATP energy exactly where your cells need it most.
Your cellular transport system is equally impressive. The Golgi apparatus functions like a post office, packaging and labelling proteins before shipping them to their destinations via transport vesicles. Lysosomes serve as the cleanup crew, using digestive enzymes to destroy unwanted materials or invading cells when necessary.
Eukaryotic cells (like yours) are far more complex than prokaryotic cells (like bacteria). Whilst your cells have membrane-bound organelles and a proper nucleus, bacterial cells keep their circular DNA floating freely in the cytoplasm. They reproduce through binary fission, simply copying their DNA and splitting in half.
Quick Check: Plant cells have everything animal cells do, plus chloroplasts for photosynthesis, a rigid cell wall, and a large vacuole for support and storage.
Sign up to see the contentIt's free!
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Viruses and Microscopy Techniques
Viruses aren't actually alive - they're basically genetic pirates that hijack your cells to reproduce. These acellular particles consist of nucleic acid wrapped in a protein coat called a capsid. They can't divide on their own, so they inject their DNA or RNA into host cells and force them to make viral copies.
Different viruses attack different cells because they need specific receptor proteins to attach. This is why some viruses only target particular cell types whilst others can infect multiple tissues.
To study these tiny structures, scientists use powerful electron microscopes. TEM (Transmission Electron Microscopy) shoots electrons through ultra-thin specimens for detailed internal views, whilst SEM (Scanning Electron Microscopy) bounces electrons off surfaces to create 3D images.
Cell fractionation lets researchers separate organelles by density using ultracentrifugation. After breaking cells open in a blender, they spin the mixture at increasing speeds - heavy nuclei settle first, then chloroplasts, mitochondria, and finally lightweight ribosomes.
Remember: Electron microscopes can only examine dead specimens in a vacuum, but they reveal details impossible to see with light microscopes.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Mitosis and Cell Division Control
Your body performs millions of mitosis events daily for growth and repair, creating two identical daughter cells from one parent cell. The process follows four main stages after interphase (when DNA replicates and organelles duplicate).
During prophase, chromosomes condense and the nuclear envelope dissolves. In metaphase, chromosomes line up centrally and attach to spindle fibres. Anaphase sees chromatids separate and move to opposite cell poles, whilst telophase reforms two nuclei as chromosomes uncoil.
The cell cycle includes growth phases (G1 and G2) surrounding DNA replication (S phase) before mitosis begins. Growth factors and specific genes carefully control this timing - when this control breaks down, cancer develops.
Malignant tumours grow rapidly and spread, making them more dangerous than slower-growing benign tumours. Cancer treatments often target dividing cells by preventing DNA replication or disrupting spindle formation, though this can unfortunately affect healthy cells too.
Key Point: Cancer occurs when normal cell division controls fail, allowing uncontrolled growth and potentially life-threatening tumour formation.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Stem Cells and Medical Applications
Stem cells are your body's master cells - undifferentiated and capable of becoming specialised cell types through a process called differentiation. You've got two main types: embryonic stem cells can become any cell type, whilst adult stem cells have more limited options.
Embryonic stem cells from 3-5 day old embryos offer incredible medical potential since they're pluripotent (can become anything). Adult stem cells from places like bone marrow are more restricted but already help treat blood disorders through transplants.
Therapeutic cloning creates embryos with identical genetic material to patients, potentially solving tissue rejection problems. However, risks include viral contamination during laboratory growth and the possibility of transmitting infections.
The biggest hurdles aren't scientific but ethical. Many people have religious or moral objections to destroying embryos for stem cells, viewing them as potential human life. Fortunately, researchers can often use leftover IVF embryos or collect stem cells from umbilical cord blood after birth - a completely safe, non-invasive alternative.
Looking Ahead: Stem cell therapy could revolutionise medicine, potentially treating everything from spinal injuries to heart disease once we overcome current limitations.
We thought you’d never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
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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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
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 Knowunity AI. 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 Knowunity AI. 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