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
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6
0
Ffion
05/12/2025
Biology
cell structure
192
•
5 Dec 2025
•
Ffion
@ffion_lm
Ever wondered what makes your cells tick? Understanding cell structure... Show more
Your body is built from eukaryotic cells - complex, organised structures packed with specialised parts called organelles. Unlike simple prokaryotic bacteria, these cells are like miniature cities with different departments handling specific tasks.
The plasma membrane acts as your cell's bouncer, controlling what gets in and out whilst responding to chemical signals like hormones. Plant cells get extra protection from a rigid cell wall made of cellulose that stops them from bursting under pressure.
At the heart of every cell sits the nucleus, your genetic control centre wrapped in a double-layered nuclear envelope with tiny pores. Inside, the nucleolus churns out ribosomes - the protein-making factories that either float freely or attach to the rough endoplasmic reticulum (RER).
The RER looks like stacked pancakes covered in ribosomes and specialises in folding proteins, while its smooth cousin (SER) handles lipid production. Vesicles act like delivery vans, shuttling materials between organelles and eventually reaching the Golgi apparatus - your cell's packaging and dispatch centre that also creates lysosomes filled with digestive enzymes.
Key Point: Mitochondria are your cellular power stations, using a double membrane structure with folded inner layers (cristae) to produce ATP through aerobic respiration.
Making proteins is like following a recipe from your genetic cookbook. The process starts when DNA gets transcribed into mRNA in the nucleus, then travels through nuclear pores to ribosomes on the RER where the actual protein assembly happens.
Once built, proteins move through the RER's internal channels, get packaged into vesicles, and travel via microtubules to the Golgi apparatus for modifications. Finally, vesicles carry the finished products to the plasma membrane for release through exocytosis - a process crucial for hormones like insulin.
Prokaryotic cells (bacteria) are completely different beasts. They're tiny (2µm), have circular DNA floating freely, and cell walls made of peptidoglycan rather than cellulose. Their flagella are simple protein helixes, nothing like the complex 9+2 microtubule arrangement in eukaryotic cells.
Eukaryotic cells are giants in comparison with linear DNA safely tucked in a nucleus, membrane-bound organelles, and a sophisticated cytoskeleton made of microtubules and microfilaments that supports, shapes, and moves cellular components.
Remember: The cytoskeleton isn't just structural - it's like your cell's internal motorway system, moving organelles and materials exactly where they need to go.
Light microscopes are your trusty workhorses - cheap, portable, and perfect for viewing living specimens up to 1500x magnification. However, their resolution maxes out at 0.2µm, meaning you'll struggle to see ribosomes or detailed organelle structures.
Laser scanning confocal microscopes create stunning 3D images by using fluorescent dyes that glow when hit with laser light. A pinhole blocks out unwanted light, producing incredibly detailed, coloured images perfect for medical research - though specimens must be dead.
Transmission electron microscopes (TEM) are the resolution champions, reaching 0.2nm and magnifying up to 2 million times. They fire electrons through ultra-thin specimens, creating detailed 2D black-and-white images where denser areas appear darker because they absorb more electrons.
Scanning electron microscopes (SEM) bounce electrons off specimen surfaces to create impressive 3D images at 200,000x magnification. Though resolution is lower than TEM (10nm), they're brilliant for studying surface structures and can even be enhanced with false colour.
Pro Tip: Always calibrate your eyepiece graticule with a stage micrometer before measuring specimens - it's your key to accurate size calculations.
Getting perfect microscope images requires proper specimen preparation. Dehydrate your samples and embed them in wax to prevent distortion, then slice them thin enough for light to pass through effectively.
Staining is your secret weapon for highlighting specific structures. Acetic orcein turns chromosomes bright red, eosin colours cytoplasm, Sudan red reveals lipids, and iodine stains cell walls yellow whilst turning starch granules blue-black.
For measurements, line up your eyepiece graticule with the stage micrometer first. If one stage division (0.1mm) equals 4.5 eyepiece divisions, then each eyepiece division = 0.022mm. A specimen spanning 20 eyepiece divisions would measure 0.44mm.
Your total magnification is simple maths: eyepiece magnification × objective lens magnification. Start with the lowest objective lens, raise the stage to maximum using the coarse adjustment, then fine-tune with the precision knob whilst looking through the eyepiece.
Essential Technique: Always tilt your cover slip when placing it to avoid air bubbles - they'll ruin your image and make measurements impossible.
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.
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
Ffion
@ffion_lm
Ever wondered what makes your cells tick? Understanding cell structure is like getting the blueprint to life itself - from the tiny organelles doing their jobs to the massive differences between simple bacteria and complex human cells.
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Your body is built from eukaryotic cells - complex, organised structures packed with specialised parts called organelles. Unlike simple prokaryotic bacteria, these cells are like miniature cities with different departments handling specific tasks.
The plasma membrane acts as your cell's bouncer, controlling what gets in and out whilst responding to chemical signals like hormones. Plant cells get extra protection from a rigid cell wall made of cellulose that stops them from bursting under pressure.
At the heart of every cell sits the nucleus, your genetic control centre wrapped in a double-layered nuclear envelope with tiny pores. Inside, the nucleolus churns out ribosomes - the protein-making factories that either float freely or attach to the rough endoplasmic reticulum (RER).
The RER looks like stacked pancakes covered in ribosomes and specialises in folding proteins, while its smooth cousin (SER) handles lipid production. Vesicles act like delivery vans, shuttling materials between organelles and eventually reaching the Golgi apparatus - your cell's packaging and dispatch centre that also creates lysosomes filled with digestive enzymes.
Key Point: Mitochondria are your cellular power stations, using a double membrane structure with folded inner layers (cristae) to produce ATP through aerobic respiration.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Making proteins is like following a recipe from your genetic cookbook. The process starts when DNA gets transcribed into mRNA in the nucleus, then travels through nuclear pores to ribosomes on the RER where the actual protein assembly happens.
Once built, proteins move through the RER's internal channels, get packaged into vesicles, and travel via microtubules to the Golgi apparatus for modifications. Finally, vesicles carry the finished products to the plasma membrane for release through exocytosis - a process crucial for hormones like insulin.
Prokaryotic cells (bacteria) are completely different beasts. They're tiny (2µm), have circular DNA floating freely, and cell walls made of peptidoglycan rather than cellulose. Their flagella are simple protein helixes, nothing like the complex 9+2 microtubule arrangement in eukaryotic cells.
Eukaryotic cells are giants in comparison with linear DNA safely tucked in a nucleus, membrane-bound organelles, and a sophisticated cytoskeleton made of microtubules and microfilaments that supports, shapes, and moves cellular components.
Remember: The cytoskeleton isn't just structural - it's like your cell's internal motorway system, moving organelles and materials exactly where they need to go.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Light microscopes are your trusty workhorses - cheap, portable, and perfect for viewing living specimens up to 1500x magnification. However, their resolution maxes out at 0.2µm, meaning you'll struggle to see ribosomes or detailed organelle structures.
Laser scanning confocal microscopes create stunning 3D images by using fluorescent dyes that glow when hit with laser light. A pinhole blocks out unwanted light, producing incredibly detailed, coloured images perfect for medical research - though specimens must be dead.
Transmission electron microscopes (TEM) are the resolution champions, reaching 0.2nm and magnifying up to 2 million times. They fire electrons through ultra-thin specimens, creating detailed 2D black-and-white images where denser areas appear darker because they absorb more electrons.
Scanning electron microscopes (SEM) bounce electrons off specimen surfaces to create impressive 3D images at 200,000x magnification. Though resolution is lower than TEM (10nm), they're brilliant for studying surface structures and can even be enhanced with false colour.
Pro Tip: Always calibrate your eyepiece graticule with a stage micrometer before measuring specimens - it's your key to accurate size calculations.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Getting perfect microscope images requires proper specimen preparation. Dehydrate your samples and embed them in wax to prevent distortion, then slice them thin enough for light to pass through effectively.
Staining is your secret weapon for highlighting specific structures. Acetic orcein turns chromosomes bright red, eosin colours cytoplasm, Sudan red reveals lipids, and iodine stains cell walls yellow whilst turning starch granules blue-black.
For measurements, line up your eyepiece graticule with the stage micrometer first. If one stage division (0.1mm) equals 4.5 eyepiece divisions, then each eyepiece division = 0.022mm. A specimen spanning 20 eyepiece divisions would measure 0.44mm.
Your total magnification is simple maths: eyepiece magnification × objective lens magnification. Start with the lowest objective lens, raise the stage to maximum using the coarse adjustment, then fine-tune with the precision knob whilst looking through the eyepiece.
Essential Technique: Always tilt your cover slip when placing it to avoid air bubbles - they'll ruin your image and make measurements impossible.
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
Explore the essential differences between light and electron microscopes, including magnification, resolution, and sample requirements. This summary covers key concepts for Edexcel Biology, ensuring you understand how to effectively use microscopes in your studies.
BiologyExplore the differences between light and electron microscopes, focusing on magnification and resolution. Learn how to calculate magnification using various units, including micrometers and nanometers. This summary provides essential insights for students studying microscopy.
BiologyMaster the essential steps for using a microscope effectively in Year 7 science. This guide covers key components such as the ocular lens, objective lenses, and stage controls, along with detailed instructions for focusing and magnification adjustments. Ideal for students preparing for exams or practical assessments.
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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
Combined Science
Sociology