Maths
Chemistry
Biology
English Language
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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
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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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5
1
Oscar66
12/12/2025
Biology
Cell ultrastructure flashcards
109
•
12 Dec 2025
•
Oscar66
@oscar66
Your cells are like incredibly complex cities, packed with specialised... Show more
Ever wondered how scientists can see inside cells? It all comes down to magnification (how much bigger something appears) and resolution (how clearly you can distinguish between two separate points). Think of it like the difference between a blurry enlarged photo and a crisp, detailed one.
The cell surface membrane acts like a selective bouncer at a club - it controls what gets in and out of your cells whilst also handling communication between cells. Inside, you'll find the nucleus, which is basically the cell's control centre containing all your genetic material and directing protein production.
Within the nucleus, heterochromatin represents the tightly packed, inactive DNA, whilst euchromatin is the loose, active form that's busy making proteins. The dark spot you might see is the nucleolus, where important cellular components are assembled.
Quick Tip: Remember that the nucleus is surrounded by a double membrane called the nuclear envelope - this keeps your precious DNA safely separated from the rest of the cell's activities.
Your cells run like efficient factories, and the rough endoplasmic reticulum is where protein production happens. Those "rough" bits are actually ribosomes - tiny protein-making machines that can be found floating freely or attached to membranes.
Ribosomes come in two sizes: 80s ribosomes in eukaryotic cells (like yours) and smaller 70s ribosomes in prokaryotes and interestingly, in mitochondria and chloroplasts too. This size difference actually hints at evolutionary history!
The smooth endoplasmic reticulum handles lipid and carbohydrate synthesis, whilst the Golgi body works like a post office - modifying, packaging, and shipping molecules around the cell using its stack of membranes called cisternae.
Lysosomes are the cell's recycling centres, packed with digestive enzymes that break down waste, old organelles, and harmful substances. They start life as vesicles from the Golgi body before becoming fully functional cleanup crews.
Remember: The ER and Golgi work together like an assembly line - rough ER makes proteins, smooth ER processes other molecules, and Golgi packages everything for delivery.
Mitochondria are your cellular powerhouses, using aerobic respiration to make ATP (your body's energy currency). Inside, the folded inner membranes called cristae house the electron transport chain, whilst the matrix contains the mitochondria's own DNA - proof of their bacterial origins.
The cell's skeleton consists of microtubules that maintain shape and help transport materials. Centrioles organise these structures and play crucial roles during cell division, determining where organelles end up.
Some cells have cilia and flagella for movement, whilst others sport microvilli - tiny finger-like projections that massively increase surface area for absorption (think intestinal cells soaking up nutrients).
Plant cells get extra features: chloroplasts for photosynthesis (with their own DNA too), rigid cell walls for structure, and plasmodesmata - channels connecting neighbouring cells. The vacuole maintains cell pressure and stores materials.
Plant Power: Chloroplasts contain thylakoids (stacked into grana) where light reactions occur, whilst the stroma handles the carbon-fixing reactions of photosynthesis.
Prokaryotes keep things simple - they're single-celled organisms with circular DNA, 70s ribosomes, and peptidoglycan cell walls. No fancy membrane-bound organelles here, just efficient basic living.
Viruses aren't even proper cells - they're just genetic material (DNA or RNA) wrapped in a protein capsid, sometimes with an outer envelope. They're the ultimate parasites, unable to survive without hijacking other cells.
Scale matters in cell biology: remember that 1000 nanometres equals 1 micrometre, and 1000 micrometres equals 1 millimetre. When using microscopes, watch out for artefacts - structures that appear during specimen preparation but aren't actually there.
Polysomes are clusters of ribosomes working together on the same protein, whilst pinocytosis describes how cells gulp down fluids by forming vesicles from their membrane.
Size Check: Most human cells are around 10-30 micrometres, bacteria are 1-5 micrometres, and viruses are typically 20-300 nanometres - that's incredibly tiny!
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.
Quotes from every main character
English LiteratureApp 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
Oscar66
@oscar66
Your cells are like incredibly complex cities, packed with specialised structures called organelles that each have specific jobs to keep you alive. Understanding cell ultrastructure means getting to know these tiny components and how they work together - it's fundamental... Show more
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Improve your grades
Join milions of students
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Ever wondered how scientists can see inside cells? It all comes down to magnification (how much bigger something appears) and resolution (how clearly you can distinguish between two separate points). Think of it like the difference between a blurry enlarged photo and a crisp, detailed one.
The cell surface membrane acts like a selective bouncer at a club - it controls what gets in and out of your cells whilst also handling communication between cells. Inside, you'll find the nucleus, which is basically the cell's control centre containing all your genetic material and directing protein production.
Within the nucleus, heterochromatin represents the tightly packed, inactive DNA, whilst euchromatin is the loose, active form that's busy making proteins. The dark spot you might see is the nucleolus, where important cellular components are assembled.
Quick Tip: Remember that the nucleus is surrounded by a double membrane called the nuclear envelope - this keeps your precious DNA safely separated from the rest of the cell's activities.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your cells run like efficient factories, and the rough endoplasmic reticulum is where protein production happens. Those "rough" bits are actually ribosomes - tiny protein-making machines that can be found floating freely or attached to membranes.
Ribosomes come in two sizes: 80s ribosomes in eukaryotic cells (like yours) and smaller 70s ribosomes in prokaryotes and interestingly, in mitochondria and chloroplasts too. This size difference actually hints at evolutionary history!
The smooth endoplasmic reticulum handles lipid and carbohydrate synthesis, whilst the Golgi body works like a post office - modifying, packaging, and shipping molecules around the cell using its stack of membranes called cisternae.
Lysosomes are the cell's recycling centres, packed with digestive enzymes that break down waste, old organelles, and harmful substances. They start life as vesicles from the Golgi body before becoming fully functional cleanup crews.
Remember: The ER and Golgi work together like an assembly line - rough ER makes proteins, smooth ER processes other molecules, and Golgi packages everything for delivery.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Mitochondria are your cellular powerhouses, using aerobic respiration to make ATP (your body's energy currency). Inside, the folded inner membranes called cristae house the electron transport chain, whilst the matrix contains the mitochondria's own DNA - proof of their bacterial origins.
The cell's skeleton consists of microtubules that maintain shape and help transport materials. Centrioles organise these structures and play crucial roles during cell division, determining where organelles end up.
Some cells have cilia and flagella for movement, whilst others sport microvilli - tiny finger-like projections that massively increase surface area for absorption (think intestinal cells soaking up nutrients).
Plant cells get extra features: chloroplasts for photosynthesis (with their own DNA too), rigid cell walls for structure, and plasmodesmata - channels connecting neighbouring cells. The vacuole maintains cell pressure and stores materials.
Plant Power: Chloroplasts contain thylakoids (stacked into grana) where light reactions occur, whilst the stroma handles the carbon-fixing reactions of photosynthesis.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Prokaryotes keep things simple - they're single-celled organisms with circular DNA, 70s ribosomes, and peptidoglycan cell walls. No fancy membrane-bound organelles here, just efficient basic living.
Viruses aren't even proper cells - they're just genetic material (DNA or RNA) wrapped in a protein capsid, sometimes with an outer envelope. They're the ultimate parasites, unable to survive without hijacking other cells.
Scale matters in cell biology: remember that 1000 nanometres equals 1 micrometre, and 1000 micrometres equals 1 millimetre. When using microscopes, watch out for artefacts - structures that appear during specimen preparation but aren't actually there.
Polysomes are clusters of ribosomes working together on the same protein, whilst pinocytosis describes how cells gulp down fluids by forming vesicles from their membrane.
Size Check: Most human cells are around 10-30 micrometres, bacteria are 1-5 micrometres, and viruses are typically 20-300 nanometres - that's incredibly tiny!
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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Explore the key differences between eukaryotic and prokaryotic cells, including animal, plant, and bacterial cell structures. This summary covers essential components such as the nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, chloroplasts, cell wall, vacuoles, plasmid DNA, and flagella, along with their functions in cellular processes.
BiologyExplore the five main kingdoms of life, focusing on the characteristics of eukaryotic cells, including protists, fungi, and their classification. This summary covers key concepts such as multicellularity, heterotrophy, and autotrophy, providing a clear overview for students studying biological classification.
BiologyExplore the essential components of cells and their functions in this detailed summary. Key topics include the nucleus, mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum, lysosomes, ribosomes, and cell walls. Ideal for A-level Biology students, this resource provides clear explanations and diagrams to enhance understanding of cellular structures and processes.
BiologyExplore the intricate structures of eukaryotic cells, focusing on the nucleus, endoplasmic reticulum, and mitochondria. This summary covers key functions, including DNA replication, protein synthesis, and ATP production, essential for A-level biology students. Ideal for exam preparation and understanding cellular processes.
BiologyExplore the key features and functions of animal and plant cells, including the roles of the nucleus, mitochondria, ribosomes, and chloroplasts. This summary provides essential insights for GCSE biology students, focusing on cell structure and the differences between plant and animal cells.
BiologyExplore the distinctions between prokaryotic and eukaryotic cells across the five kingdoms: Prokaryotae, Protoctista, Fungi, Plantae, and Animalia. This summary covers cellular structures, functions, and key characteristics, including ribosome types, DNA structure, and nutritional modes. Ideal for students studying cellular biology and taxonomy.
BiologyQuotes from every main character
English LiteratureApp 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