Every living thing is made up of cells - they're... Show more
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16 Jan 2026
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KS3 Biology Revision: Cells and Microscopes Explained
summer
@summer_pexs
1 / 4
Cell Structure and Function
Think of a cell as a miniature factory with different parts doing specific jobs to keep everything running smoothly. The nucleus acts like the boss, controlling everything the cell does whilst storing all the genetic material (DNA) that makes you unique.
The cytoplasm is where all the action happens - it's a jelly-like substance where chemical reactions take place constantly. Meanwhile, the mitochondria work as the cell's power stations, using aerobic respiration to create energy for all cellular activities.
The cell membrane works like a security guard, carefully controlling what enters and exits the cell. Plant cells have extra features: a strong cell wall for support, vacuoles filled with sap (dissolved salts and sugars), and chloroplasts that make photosynthesis possible.
Quick Tip: Remember that without chloroplasts, plants couldn't photosynthesise and produce the oxygen we breathe!
Using a Microscope
Microscopes are your gateway to exploring the invisible world of cells! Understanding magnification is crucial - it tells you how much bigger an object appears compared to its actual size.
To calculate total magnification, simply multiply the eyepiece magnification by the objective lens magnification. For example: 10× eyepiece × 40× objective lens = 400× total magnification.
Key microscope parts include the stage (where you place slides), body tube (connects eyepiece to objectives), and focus knobs. Use the coarse focus knob first to get roughly in focus, then fine-tune with the fine focus knob. The iris diaphragm controls light levels for clearer viewing.
Pro Tip: Always start with low power objectives before switching to high power - it makes finding your specimen much easier!
Preparing Microscope Slides
Making your own microscope slides is simpler than you might think! Start by collecting your specimen - this could be anything from onion skin to pond water.
Place your specimen carefully onto a clean slide, then add a drop of iodine stain. This stain makes cell structures (organelles) much easier to see by creating contrast.
Gently lower a cover slip over your specimen to protect it and prevent air bubbles. Finally, place the slide onto the microscope stage and you're ready to explore!
Remember: Adding iodine might seem like an extra step, but it's the difference between seeing blurry shapes and clearly defined cell structures!
From Cells to Organisms
Your body follows an amazing organisational system: cells group together to form tissues, tissues combine to create organs, and organs work together as organ systems. It's like building with increasingly complex Lego sets!
Single-celled organisms like amoeba and euglena are fascinating because they must do everything within just one cell. Amoebas move by growing false feet and eat by engulfing prey, whilst euglenas swim using their flagellum .
Both organisms respire by allowing oxygen to diffuse through their cell membrane and carbon dioxide to exit the same way. They reproduce simply by splitting in two! Euglenas are particularly clever - they have an eyespot that detects light for photosynthesis.
Amazing Fact: When amoebas sense danger, they curl up into a protective ball - it's like having a built-in panic room!
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4.8/5
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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 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
KS3 Biology Revision: Cells and Microscopes Explained
summer
@summer_pexs
Every living thing is made up of cells - they're like tiny building blocks that keep us alive! Understanding how cells work and how to observe them under a microscope will help you grasp the basics of all life on... Show more
Cell Structure and Function
Think of a cell as a miniature factory with different parts doing specific jobs to keep everything running smoothly. The nucleus acts like the boss, controlling everything the cell does whilst storing all the genetic material (DNA) that makes you unique.
The cytoplasm is where all the action happens - it's a jelly-like substance where chemical reactions take place constantly. Meanwhile, the mitochondria work as the cell's power stations, using aerobic respiration to create energy for all cellular activities.
The cell membrane works like a security guard, carefully controlling what enters and exits the cell. Plant cells have extra features: a strong cell wall for support, vacuoles filled with sap (dissolved salts and sugars), and chloroplasts that make photosynthesis possible.
Quick Tip: Remember that without chloroplasts, plants couldn't photosynthesise and produce the oxygen we breathe!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Using a Microscope
Microscopes are your gateway to exploring the invisible world of cells! Understanding magnification is crucial - it tells you how much bigger an object appears compared to its actual size.
To calculate total magnification, simply multiply the eyepiece magnification by the objective lens magnification. For example: 10× eyepiece × 40× objective lens = 400× total magnification.
Key microscope parts include the stage (where you place slides), body tube (connects eyepiece to objectives), and focus knobs. Use the coarse focus knob first to get roughly in focus, then fine-tune with the fine focus knob. The iris diaphragm controls light levels for clearer viewing.
Pro Tip: Always start with low power objectives before switching to high power - it makes finding your specimen much easier!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Preparing Microscope Slides
Making your own microscope slides is simpler than you might think! Start by collecting your specimen - this could be anything from onion skin to pond water.
Place your specimen carefully onto a clean slide, then add a drop of iodine stain. This stain makes cell structures (organelles) much easier to see by creating contrast.
Gently lower a cover slip over your specimen to protect it and prevent air bubbles. Finally, place the slide onto the microscope stage and you're ready to explore!
Remember: Adding iodine might seem like an extra step, but it's the difference between seeing blurry shapes and clearly defined cell structures!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
From Cells to Organisms
Your body follows an amazing organisational system: cells group together to form tissues, tissues combine to create organs, and organs work together as organ systems. It's like building with increasingly complex Lego sets!
Single-celled organisms like amoeba and euglena are fascinating because they must do everything within just one cell. Amoebas move by growing false feet and eat by engulfing prey, whilst euglenas swim using their flagellum .
Both organisms respire by allowing oxygen to diffuse through their cell membrane and carbon dioxide to exit the same way. They reproduce simply by splitting in two! Euglenas are particularly clever - they have an eyespot that detects light for photosynthesis.
Amazing Fact: When amoebas sense danger, they curl up into a protective ball - it's like having a built-in panic room!
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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4.9/5
App Store
4.8/5
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