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Updated Mar 17, 2026
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Comprehensive Notes on Cell Structure
E
emma preston
@emmapreston
1 / 4
Cell Membranes and Basic Structure
Think of the cell membrane as a bouncer at a club - it decides what gets in and what stays out. This selective permeability means oxygen and glucose can enter your cells, but harmful substances like excess sodium ions are blocked.
The membrane isn't just a simple barrier though. It's made of a phospholipid bilayer - imagine a sandwich where the bread slices are water-loving (hydrophilic) phosphate heads and the filling is water-hating (hydrophobic) lipid tails. Proteins scattered throughout act like doorways and sensors.
Inside the membrane, cytoplasm acts like jelly that holds all the cell's parts in place. The liquid part without organelles is called cytosol, and it's packed with sugars that help with important processes like diffusion and osmosis. Every cell - whether animal or plant - has this essential setup.
Quick Tip: Remember that hydrophilic = water-loving and hydrophobic = water-fearing. The membrane structure keeps the cell's insides separate from the watery environment outside.
Plant-Specific Structures and Cellular Factories
Plant cells have some extra features that animal cells don't need. The cell wall made of cellulose acts like armour, giving plants strength and support since they can't run away from danger like animals can. Unlike the selective cell membrane, the cell wall is fully permeable.
Chloroplasts are where the magic of photosynthesis happens - they're green because of chlorophyll, the pigment that captures sunlight. These are exclusive to plant cells and basically turn your garden into a solar power station.
Both plant and animal cells have the endoplasmic reticulum (ER), which is like the cell's production line. It's a network of interconnected tubes that makes important fats, stores calcium, and produces hormones. The Golgi apparatus works as the packaging and shipping department, taking proteins and lipids from the ER and sending them where they need to go.
Remember: Only plant cells have chloroplasts and cell walls - these features help plants make their own food and stand upright without bones!
Comparing Animal and Plant Cells
Now you can see the key differences side by side. Animal cells are more compact and flexible, with organelles like the nucleus, mitochondria, ribosomes, and both rough and smooth endoplasmic reticulum floating in the cytoplasm.
Plant cells have all the same organelles as animal cells, but they're supersized in some ways. They have a massive central vacuole that helps maintain the plant's shape and stores water. The cell wall provides the rigid structure that lets trees grow hundreds of feet tall.
Both cell types share the essential organelles - the nucleus (control centre), mitochondria (powerhouses), ribosomes (protein makers), and the Golgi apparatus (packaging centre). The main difference is that plant cells have extra equipment for making food and staying upright.
Study Hack: When drawing cell diagrams, start with the basic animal cell structure, then add the cell wall, chloroplasts, and large vacuole to create a plant cell.
Prokaryotic vs Eukaryotic Cells
Here's a major divide in the living world: prokaryotic cells are the simpler, older type without a nucleus or membrane-bound organelles. Think bacteria - they're like studio apartments where everything happens in one room.
Eukaryotic cells are the complex type you've been studying, with a nucleus and specialised organelles. These include animals, plants, fungi, and single-celled organisms like amoeba. They're like mansions with different rooms for different functions.
Don't confuse cell complexity with organism complexity though. Unicellular organisms (like bacteria or amoeba) are made of just one cell, while multicellular organisms (like you!) are made of billions of cells working together.
Key Point: All the cell structures you've learned about (nucleus, mitochondria, ER) only exist in eukaryotic cells - prokaryotes keep things much simpler.
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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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I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
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Brad T
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Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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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Greenlight Bonnie
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Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Comprehensive Notes on Cell Structure
E
emma preston
@emmapreston
Your cells are like tiny factories with specialised parts working together to keep you alive. Understanding cell structure is crucial for biology - it explains how life works at its most basic level and sets the foundation for everything from... Show more
Cell Membranes and Basic Structure
Think of the cell membrane as a bouncer at a club - it decides what gets in and what stays out. This selective permeability means oxygen and glucose can enter your cells, but harmful substances like excess sodium ions are blocked.
The membrane isn't just a simple barrier though. It's made of a phospholipid bilayer - imagine a sandwich where the bread slices are water-loving (hydrophilic) phosphate heads and the filling is water-hating (hydrophobic) lipid tails. Proteins scattered throughout act like doorways and sensors.
Inside the membrane, cytoplasm acts like jelly that holds all the cell's parts in place. The liquid part without organelles is called cytosol, and it's packed with sugars that help with important processes like diffusion and osmosis. Every cell - whether animal or plant - has this essential setup.
Quick Tip: Remember that hydrophilic = water-loving and hydrophobic = water-fearing. The membrane structure keeps the cell's insides separate from the watery environment outside.
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Plant-Specific Structures and Cellular Factories
Plant cells have some extra features that animal cells don't need. The cell wall made of cellulose acts like armour, giving plants strength and support since they can't run away from danger like animals can. Unlike the selective cell membrane, the cell wall is fully permeable.
Chloroplasts are where the magic of photosynthesis happens - they're green because of chlorophyll, the pigment that captures sunlight. These are exclusive to plant cells and basically turn your garden into a solar power station.
Both plant and animal cells have the endoplasmic reticulum (ER), which is like the cell's production line. It's a network of interconnected tubes that makes important fats, stores calcium, and produces hormones. The Golgi apparatus works as the packaging and shipping department, taking proteins and lipids from the ER and sending them where they need to go.
Remember: Only plant cells have chloroplasts and cell walls - these features help plants make their own food and stand upright without bones!
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Comparing Animal and Plant Cells
Now you can see the key differences side by side. Animal cells are more compact and flexible, with organelles like the nucleus, mitochondria, ribosomes, and both rough and smooth endoplasmic reticulum floating in the cytoplasm.
Plant cells have all the same organelles as animal cells, but they're supersized in some ways. They have a massive central vacuole that helps maintain the plant's shape and stores water. The cell wall provides the rigid structure that lets trees grow hundreds of feet tall.
Both cell types share the essential organelles - the nucleus (control centre), mitochondria (powerhouses), ribosomes (protein makers), and the Golgi apparatus (packaging centre). The main difference is that plant cells have extra equipment for making food and staying upright.
Study Hack: When drawing cell diagrams, start with the basic animal cell structure, then add the cell wall, chloroplasts, and large vacuole to create a plant cell.
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Prokaryotic vs Eukaryotic Cells
Here's a major divide in the living world: prokaryotic cells are the simpler, older type without a nucleus or membrane-bound organelles. Think bacteria - they're like studio apartments where everything happens in one room.
Eukaryotic cells are the complex type you've been studying, with a nucleus and specialised organelles. These include animals, plants, fungi, and single-celled organisms like amoeba. They're like mansions with different rooms for different functions.
Don't confuse cell complexity with organism complexity though. Unicellular organisms (like bacteria or amoeba) are made of just one cell, while multicellular organisms (like you!) are made of billions of cells working together.
Key Point: All the cell structures you've learned about (nucleus, mitochondria, ER) only exist in eukaryotic cells - prokaryotes keep things much simpler.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user