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Updated Mar 25, 2026
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Comprehensive Biology Cells Glossary for A-Level Students
leah :)
@sharkido
1 / 3
Cell Structure and Organelles
Every cell is like a bustling city with specialised districts doing different jobs. The nucleus acts as city hall, containing all the DNA instructions and controlling what happens throughout the cell. It's surrounded by two membranes with pores that act like security checkpoints.
The cytoplasm is the jelly-like substance where all the action happens - think of it as the streets where organelles move around safely. Mitochondria are the power stations, using oxygen to make ATP energy through aerobic respiration. In plant cells, chloroplasts work like solar panels, capturing sunlight to make glucose through photosynthesis.
The endoplasmic reticulum comes in two types: rough ER (covered in ribosomes) makes proteins, while smooth ER produces lipids. The Golgi apparatus works like a post office, packaging and modifying proteins before shipping them out in vesicles. Lysosomes are the cleanup crew, breaking down waste with powerful enzymes.
Quick Tip: Remember that plant cells have extra features like cell walls for structure and large vacuoles for storage - up to 80% of the cell volume!
Cell Types and Division
Eukaryotic cells (like yours) have a nucleus and organised compartments, whilst prokaryotic cells (bacteria) have their DNA floating freely in the cytoplasm. Eukaryotes are typically 10-100 times larger than prokaryotes and can reproduce sexually through complex processes.
Mitosis is how your body makes new cells for growth and repair. The cell cycle includes G1 (growth), S (DNA copying), G2 (error checking), then mitosis itself. During mitosis, chromosomes condense and line up in the middle (metaphase), get pulled apart (anaphase), and finally the cell splits in two (cytokinesis).
Centrioles build the spindle fibres that grab chromosomes by their centromeres and drag them to opposite ends of the cell. This ensures each new cell gets exactly the same genetic information. Prokaryotes use the simpler binary fission - just copying their DNA and splitting in half.
Exam Focus: Learn the four stages of mitosis in order: prophase, metaphase, anaphase, telophase. Many exam questions test this sequence!
Cell Membranes and Transport
Your cell membrane is like a selective bouncer at a club - it decides what gets in and what stays out. Made of phospholipids with hydrophilic heads facing outward and hydrophobic tails inward, this creates a barrier that's flexible yet strong. Cholesterol molecules wedged between phospholipids control how fluid the membrane stays.
Diffusion happens when molecules naturally spread from high to low concentration areas - no energy needed. Small molecules like oxygen slip straight through (simple diffusion), whilst larger or charged molecules need protein helpers for facilitated diffusion. Temperature, concentration gradients, and surface area all affect how fast diffusion occurs.
Active transport is like swimming upstream - it moves substances against their concentration gradient using ATP energy and carrier proteins. Co-transport is clever teamwork where one substance hitches a ride with another that's already moving across the membrane.
Real-world Connection: When you're dehydrated, your cells use active transport to grab every bit of water and salt they can from your kidneys - that's why your urine becomes concentrated!
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This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
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Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
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Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
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
Comprehensive Biology Cells Glossary for A-Level Students
leah :)
@sharkido
Cell biology is absolutely everywhere around you - from the food you digest to the muscles you use to scroll through your phone. Understanding how cells work gives you the keys to unlock everything from why you get tired after... Show more
Cell Structure and Organelles
Every cell is like a bustling city with specialised districts doing different jobs. The nucleus acts as city hall, containing all the DNA instructions and controlling what happens throughout the cell. It's surrounded by two membranes with pores that act like security checkpoints.
The cytoplasm is the jelly-like substance where all the action happens - think of it as the streets where organelles move around safely. Mitochondria are the power stations, using oxygen to make ATP energy through aerobic respiration. In plant cells, chloroplasts work like solar panels, capturing sunlight to make glucose through photosynthesis.
The endoplasmic reticulum comes in two types: rough ER (covered in ribosomes) makes proteins, while smooth ER produces lipids. The Golgi apparatus works like a post office, packaging and modifying proteins before shipping them out in vesicles. Lysosomes are the cleanup crew, breaking down waste with powerful enzymes.
Quick Tip: Remember that plant cells have extra features like cell walls for structure and large vacuoles for storage - up to 80% of the cell volume!
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Access to all documents
Improve your grades
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Cell Types and Division
Eukaryotic cells (like yours) have a nucleus and organised compartments, whilst prokaryotic cells (bacteria) have their DNA floating freely in the cytoplasm. Eukaryotes are typically 10-100 times larger than prokaryotes and can reproduce sexually through complex processes.
Mitosis is how your body makes new cells for growth and repair. The cell cycle includes G1 (growth), S (DNA copying), G2 (error checking), then mitosis itself. During mitosis, chromosomes condense and line up in the middle (metaphase), get pulled apart (anaphase), and finally the cell splits in two (cytokinesis).
Centrioles build the spindle fibres that grab chromosomes by their centromeres and drag them to opposite ends of the cell. This ensures each new cell gets exactly the same genetic information. Prokaryotes use the simpler binary fission - just copying their DNA and splitting in half.
Exam Focus: Learn the four stages of mitosis in order: prophase, metaphase, anaphase, telophase. Many exam questions test this sequence!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Cell Membranes and Transport
Your cell membrane is like a selective bouncer at a club - it decides what gets in and what stays out. Made of phospholipids with hydrophilic heads facing outward and hydrophobic tails inward, this creates a barrier that's flexible yet strong. Cholesterol molecules wedged between phospholipids control how fluid the membrane stays.
Diffusion happens when molecules naturally spread from high to low concentration areas - no energy needed. Small molecules like oxygen slip straight through (simple diffusion), whilst larger or charged molecules need protein helpers for facilitated diffusion. Temperature, concentration gradients, and surface area all affect how fast diffusion occurs.
Active transport is like swimming upstream - it moves substances against their concentration gradient using ATP energy and carrier proteins. Co-transport is clever teamwork where one substance hitches a ride with another that's already moving across the membrane.
Real-world Connection: When you're dehydrated, your cells use active transport to grab every bit of water and salt they can from your kidneys - that's why your urine becomes concentrated!
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?
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4.6/5
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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