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7 Dec 2025
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GCSE Double Award: Cell Biology Basics
L
lucy flanagan
@lucyflanagan_klco
1 / 6
Cell Structure Basics
Every living thing is made of cells, but not all cells are the same! Animal and plant cells both have several key parts that keep them alive and functioning.
The cell membrane acts like a bouncer at a club - it controls what gets in and out of the cell. Inside, the cytoplasm is a gel-like substance where most chemical reactions happen. The nucleus is the control centre containing genetic material, whilst ribosomes are the protein-making factories.
Plant cells have some extra features that animal cells don't. They've got a tough cell wall for support, a large permanent vacuole filled with cell sap, and chloroplasts containing chlorophyll for photosynthesis.
Bacterial cells are much simpler and smaller - they're called prokaryotic because they don't have a proper nucleus. Instead, their DNA floats around as a circular loop, plus some tiny rings called plasmids.
Quick tip: Remember the magnification formula: Image size ÷ Real size = Magnification
Stem Cells and Their Potential
Stem cells are like blank canvases - they're undifferentiated cells that can become almost any type of cell your body needs. This makes them incredibly valuable for medical treatments.
These cells could revolutionise medicine by replacing damaged blood cells or faulty organs. Scientists can even modify them to match a patient's genetic information, reducing the risk of rejection. However, there are risks - lab-grown cells might become contaminated and actually harm patients.
The debate around human embryonic stem cells is intense. Supporters argue that curing diseases is more important than concerns about embryos, whilst opponents believe we should find alternative treatments that don't involve embryos.
Plant stem cells are much less controversial and equally useful. They can create clones of rare species, help farmers grow crops with desirable features like disease resistance, and produce large numbers of identical plants quickly and cheaply.
Did you know? Unlike human stem cells, plant stem cells can regenerate entire organisms from just a small cutting!
Cell Specialisation
Differentiation is how cells transform from generic stem cells into specialists with specific jobs. Once differentiated, these cells become perfectly adapted for their particular function.
Sperm cells are built for one mission - reaching the egg. They have streamlined heads for swimming efficiently and long tails for propulsion, plus loads of mitochondria to power their journey. Nerve cells are the body's electrical cables, with long extensions and branched connections forming networks throughout your body.
Muscle cells are packed with mitochondria to generate energy for contraction, making them long and strong. Root hair cells have tiny projections that massively increase their surface area for absorbing water and minerals from soil.
Transport cells like xylem and xylem are basically biological pipes. Xylem cells are completely hollow tubes for moving water, whilst phloem cells have minimal internal structures so nutrients can flow freely through them.
Memory trick: Think of specialised cells like different jobs - each one has the right tools and shape for what it needs to do!
Diffusion Fundamentals
Diffusion is nature's way of spreading things out evenly - particles naturally move from crowded areas to less crowded ones through a semipermeable membrane. The best part? It happens automatically without using any energy.
Three main factors control how fast diffusion occurs. Temperature speeds things up because particles have more kinetic energy and move faster. Concentration gradients drive the process - the bigger the difference between high and low areas, the faster particles move.
Surface area also matters hugely - more membrane means more space for particles to cross. This is why your lungs have millions of tiny air sacs rather than just being big empty bags.
Organisms have evolved brilliant adaptations for exchange surfaces: thin membranes reduce the distance particles travel, large surface areas speed up transfer, and good blood or air supply keeps materials moving efficiently.
Real-world example: When you smell food cooking from another room, that's diffusion in action - odour molecules spreading through the air!
Osmosis Explained
Osmosis is diffusion's more specific cousin - it only deals with water molecules moving through partially permeable membranes. Water always moves from areas with high water concentration to areas with low water concentration.
Think of it like this: if you put a potato in salty water, the salt can't cross the membrane, but water can. Since there's less water outside the potato (because salt takes up space), water moves out of the potato cells.
Both osmosis and diffusion are passive processes moving from high to low concentration without needing energy. The key difference? Osmosis only moves water molecules, whilst diffusion can move any type of particle.
You can observe this in practical experiments - potatoes lose mass in salty water because water leaves the cells. If the salt concentration gets too high, cells become plasmolysed, meaning the cell membrane pulls away from the cell wall.
Lab tip: In osmosis experiments, higher salt concentration always means greater mass loss in plant tissues!
Active Transport and Exchange Systems
Sometimes cells need to move substances against the concentration gradient - from low to high concentration. This is active transport, and unlike diffusion and osmosis, it requires energy to work.
Root hair cells use active transport to absorb mineral ions from soil, even when there are more minerals inside the cell than outside. This energy-requiring process ensures plants get essential nutrients regardless of soil conditions.
Your body has amazing specialised exchange systems. Lungs contain millions of alveoli with enormous surface area, moist linings for gas dissolution, and thin walls with excellent blood supply. Villi in your small intestine have single-layer cells and rich blood supply for rapid nutrient absorption.
Fish gills are equally impressive - gill filaments covered in lamellae create massive surface area, whilst dense capillary networks speed up diffusion. These adaptations ensure efficient gas exchange in water.
Remember: Active transport is the only process that can move substances uphill against concentration gradients!
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Best app on earth! no words because it’s too good
Thomas R
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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.
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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
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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
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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
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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
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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
GCSE Double Award: Cell Biology Basics
L
lucy flanagan
@lucyflanagan_klco
Cell biology is all about understanding how the basic units of life work and interact. From the tiny structures inside cells to how they transport materials and specialise for different jobs, these concepts explain everything from why you need to... Show more
Cell Structure Basics
Every living thing is made of cells, but not all cells are the same! Animal and plant cells both have several key parts that keep them alive and functioning.
The cell membrane acts like a bouncer at a club - it controls what gets in and out of the cell. Inside, the cytoplasm is a gel-like substance where most chemical reactions happen. The nucleus is the control centre containing genetic material, whilst ribosomes are the protein-making factories.
Plant cells have some extra features that animal cells don't. They've got a tough cell wall for support, a large permanent vacuole filled with cell sap, and chloroplasts containing chlorophyll for photosynthesis.
Bacterial cells are much simpler and smaller - they're called prokaryotic because they don't have a proper nucleus. Instead, their DNA floats around as a circular loop, plus some tiny rings called plasmids.
Quick tip: Remember the magnification formula: Image size ÷ Real size = Magnification
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Stem Cells and Their Potential
Stem cells are like blank canvases - they're undifferentiated cells that can become almost any type of cell your body needs. This makes them incredibly valuable for medical treatments.
These cells could revolutionise medicine by replacing damaged blood cells or faulty organs. Scientists can even modify them to match a patient's genetic information, reducing the risk of rejection. However, there are risks - lab-grown cells might become contaminated and actually harm patients.
The debate around human embryonic stem cells is intense. Supporters argue that curing diseases is more important than concerns about embryos, whilst opponents believe we should find alternative treatments that don't involve embryos.
Plant stem cells are much less controversial and equally useful. They can create clones of rare species, help farmers grow crops with desirable features like disease resistance, and produce large numbers of identical plants quickly and cheaply.
Did you know? Unlike human stem cells, plant stem cells can regenerate entire organisms from just a small cutting!
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Cell Specialisation
Differentiation is how cells transform from generic stem cells into specialists with specific jobs. Once differentiated, these cells become perfectly adapted for their particular function.
Sperm cells are built for one mission - reaching the egg. They have streamlined heads for swimming efficiently and long tails for propulsion, plus loads of mitochondria to power their journey. Nerve cells are the body's electrical cables, with long extensions and branched connections forming networks throughout your body.
Muscle cells are packed with mitochondria to generate energy for contraction, making them long and strong. Root hair cells have tiny projections that massively increase their surface area for absorbing water and minerals from soil.
Transport cells like xylem and xylem are basically biological pipes. Xylem cells are completely hollow tubes for moving water, whilst phloem cells have minimal internal structures so nutrients can flow freely through them.
Memory trick: Think of specialised cells like different jobs - each one has the right tools and shape for what it needs to do!
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Diffusion Fundamentals
Diffusion is nature's way of spreading things out evenly - particles naturally move from crowded areas to less crowded ones through a semipermeable membrane. The best part? It happens automatically without using any energy.
Three main factors control how fast diffusion occurs. Temperature speeds things up because particles have more kinetic energy and move faster. Concentration gradients drive the process - the bigger the difference between high and low areas, the faster particles move.
Surface area also matters hugely - more membrane means more space for particles to cross. This is why your lungs have millions of tiny air sacs rather than just being big empty bags.
Organisms have evolved brilliant adaptations for exchange surfaces: thin membranes reduce the distance particles travel, large surface areas speed up transfer, and good blood or air supply keeps materials moving efficiently.
Real-world example: When you smell food cooking from another room, that's diffusion in action - odour molecules spreading through the air!
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Osmosis Explained
Osmosis is diffusion's more specific cousin - it only deals with water molecules moving through partially permeable membranes. Water always moves from areas with high water concentration to areas with low water concentration.
Think of it like this: if you put a potato in salty water, the salt can't cross the membrane, but water can. Since there's less water outside the potato (because salt takes up space), water moves out of the potato cells.
Both osmosis and diffusion are passive processes moving from high to low concentration without needing energy. The key difference? Osmosis only moves water molecules, whilst diffusion can move any type of particle.
You can observe this in practical experiments - potatoes lose mass in salty water because water leaves the cells. If the salt concentration gets too high, cells become plasmolysed, meaning the cell membrane pulls away from the cell wall.
Lab tip: In osmosis experiments, higher salt concentration always means greater mass loss in plant tissues!
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Active Transport and Exchange Systems
Sometimes cells need to move substances against the concentration gradient - from low to high concentration. This is active transport, and unlike diffusion and osmosis, it requires energy to work.
Root hair cells use active transport to absorb mineral ions from soil, even when there are more minerals inside the cell than outside. This energy-requiring process ensures plants get essential nutrients regardless of soil conditions.
Your body has amazing specialised exchange systems. Lungs contain millions of alveoli with enormous surface area, moist linings for gas dissolution, and thin walls with excellent blood supply. Villi in your small intestine have single-layer cells and rich blood supply for rapid nutrient absorption.
Fish gills are equally impressive - gill filaments covered in lamellae create massive surface area, whilst dense capillary networks speed up diffusion. These adaptations ensure efficient gas exchange in water.
Remember: Active transport is the only process that can move substances uphill against concentration gradients!
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What is the Knowunity AI companion?
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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 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