Biology
Chemistry
AP Chemistry
English
AP English Literature
Biology
Dec 5, 2025
65
3 pages
Yujun Ge @yujunge_jflh
The cell membrane is the protective barrier that surrounds every living cell, controlling what enters and exits. This... Show more
Ever wondered how your cells decide what to let in and keep out? The cell membrane acts like a smart security system for every cell in your body. It serves three main functions regulating what enters and exits the cell, protecting the cell's contents, and providing structural support.
The cell membrane is composed of three key components. Phospholipids form the main structure with their water-loving (hydrophilic) heads and water-fearing (hydrophobic) tails. Proteins embedded throughout act as doorways for specific molecules. Carbohydrates attached to the outer surface help cells recognize each other.
Phospholipids arrange themselves in a special way called a lipid bilayer. The hydrophilic heads face outward toward watery environments both inside and outside the cell, while the hydrophobic tails hide in the middle away from water. Some tails are straight (saturated fats), while others have bends (unsaturated fats).
Quick Tip Think of the cell membrane like a school with security guards (proteins) that check IDs before allowing people (molecules) to enter or exit, while the building itself (phospholipids) forms the protective structure.
The phospholipids in cell membranes form a bilayer - two layers with heads facing outward and tails tucked inside. This arrangement creates a flexible but secure barrier around the cell.
Proteins in the membrane come in two types peripheral proteins that sit on the surface and integral proteins that extend through the entire bilayer. These integral proteins form channels that allow specific substances to pass through that couldn't otherwise cross the phospholipid barrier.
Carbohydrates attach to proteins on the exterior surface of the membrane. These sugar chains function as identification tags, helping cells recognize one another - like name badges at a conference that help people know who they're talking to.
The cell membrane is semi-permeable, meaning it's selective about what passes through. Small uncharged polar molecules (like water) and hydrophobic molecules (like oxygen) can pass through freely. However, ions (like sodium or chloride) and large polar molecules (like glucose) cannot cross without help from membrane proteins.
Your cell membrane acts like a sophisticated filter, allowing only certain substances to pass through based on their size and chemical properties. This selective permeability is crucial for maintaining the cell's internal environment.
Hydrophobic molecules like oxygen (O₂), carbon dioxide (CO₂), and steroids can easily pass through the membrane's fatty interior. Their non-polar nature makes them compatible with the hydrophobic tails of the phospholipids.
Small uncharged polar molecules including water, glycerol, urea, and ethanol can also cross the membrane, though not as easily as hydrophobic molecules. Their small size allows them to slip through small spaces in the lipid bilayer.
Remember This The membrane keeps out two key types of molecules large uncharged polar molecules (like glucose and sucrose) and ions (like Na⁺, K⁺, Cl⁻). These substances need special protein channels or transporters to enter or exit the cell!
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.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Gives a diagram of both a plant and animal cell and explains parts of the cell
BiologyInventors
BiologyExplore the key organelles in plant and animal cells, including their functions and differences. This summary covers the nucleus, mitochondria, ribosomes, chloroplasts, vacuoles, and more, providing essential insights for understanding cell biology.
BiologyDifferences include shape, cell wall, chloroplasts, food, vacuoles, centrioles, lysosomes and fun fact about Robert Brown
Environmental ScienceWhole first Semester of Biology
BiologyNotes with images, descriptions, and makeup of cell parts and organelles. Honors Biology (9th-10th grades)
BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
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 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 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 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 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
Yujun Ge
@yujunge_jflh
The cell membrane is the protective barrier that surrounds every living cell, controlling what enters and exits. This essential structure not only shields the cell's contents but also facilitates communication with other cells and manages the movement of nutrients and... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered how your cells decide what to let in and keep out? The cell membrane acts like a smart security system for every cell in your body. It serves three main functions: regulating what enters and exits the cell, protecting the cell's contents, and providing structural support.
The cell membrane is composed of three key components. Phospholipids form the main structure with their water-loving (hydrophilic) heads and water-fearing (hydrophobic) tails. Proteins embedded throughout act as doorways for specific molecules. Carbohydrates attached to the outer surface help cells recognize each other.
Phospholipids arrange themselves in a special way called a lipid bilayer. The hydrophilic heads face outward toward watery environments both inside and outside the cell, while the hydrophobic tails hide in the middle away from water. Some tails are straight (saturated fats), while others have bends (unsaturated fats).
Quick Tip: Think of the cell membrane like a school with security guards (proteins) that check IDs before allowing people (molecules) to enter or exit, while the building itself (phospholipids) forms the protective structure.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The phospholipids in cell membranes form a bilayer - two layers with heads facing outward and tails tucked inside. This arrangement creates a flexible but secure barrier around the cell.
Proteins in the membrane come in two types: peripheral proteins that sit on the surface and integral proteins that extend through the entire bilayer. These integral proteins form channels that allow specific substances to pass through that couldn't otherwise cross the phospholipid barrier.
Carbohydrates attach to proteins on the exterior surface of the membrane. These sugar chains function as identification tags, helping cells recognize one another - like name badges at a conference that help people know who they're talking to.
The cell membrane is semi-permeable, meaning it's selective about what passes through. Small uncharged polar molecules (like water) and hydrophobic molecules (like oxygen) can pass through freely. However, ions (like sodium or chloride) and large polar molecules (like glucose) cannot cross without help from membrane proteins.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your cell membrane acts like a sophisticated filter, allowing only certain substances to pass through based on their size and chemical properties. This selective permeability is crucial for maintaining the cell's internal environment.
Hydrophobic molecules like oxygen (O₂), carbon dioxide (CO₂), and steroids can easily pass through the membrane's fatty interior. Their non-polar nature makes them compatible with the hydrophobic tails of the phospholipids.
Small uncharged polar molecules including water, glycerol, urea, and ethanol can also cross the membrane, though not as easily as hydrophobic molecules. Their small size allows them to slip through small spaces in the lipid bilayer.
Remember This: The membrane keeps out two key types of molecules: large uncharged polar molecules (like glucose and sucrose) and ions (like Na⁺, K⁺, Cl⁻). These substances need special protein channels or transporters to enter or exit the cell!
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.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Gives a diagram of both a plant and animal cell and explains parts of the cell
BiologyInventors
BiologyExplore the key organelles in plant and animal cells, including their functions and differences. This summary covers the nucleus, mitochondria, ribosomes, chloroplasts, vacuoles, and more, providing essential insights for understanding cell biology.
BiologyDifferences include shape, cell wall, chloroplasts, food, vacuoles, centrioles, lysosomes and fun fact about Robert Brown
Environmental ScienceWhole first Semester of Biology
BiologyNotes with images, descriptions, and makeup of cell parts and organelles. Honors Biology (9th-10th grades)
BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
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 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 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 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 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
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