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Understanding Cell Basics
Cells are the basic units of life that demonstrate emergent properties—individual organelles can't sustain life alone, but when organized within a cell membrane, they create living systems. These microscopic structures are the foundation of all living organisms.
There are two primary types of cells: prokaryotic and eukaryotic. Prokaryotic cells (including bacteria and archaea) evolved first, about 3.5 billion years ago. They lack a nucleus and membrane-bound organelles, though they do contain ribosomes. The oldest fossil evidence of these ancient cells can be found in stromatolites in Shark Bay, Australia.
Eukaryotic cells developed later and feature a membrane-bound nucleus and organelles. All organisms except bacteria and archaea are composed of eukaryotic cells. They're generally larger and more complex than their prokaryotic counterparts.
💡 The Endosymbiotic Hypothesis explains how eukaryotic cells evolved: smaller prokaryotes began living inside larger ones in mutually beneficial relationships. Over time, these smaller organisms evolved into organelles like mitochondria and chloroplasts.
Evidence for Endosymbiosis & Cell Dynamics
The evidence supporting the endosymbiotic theory is compelling when we examine mitochondria and chloroplasts. These organelles maintain their own circular chromosomes similar to bacteria, contain bacteria-like ribosomes, and can reproduce independently within eukaryotic cells. Their double phospholipid bilayer membranes suggest they were once free-living organisms that were engulfed.
A crucial concept in cell biology is the surface area-to-volume ratio. As cells grow larger, their surface area increases more slowly than their volume. This ratio is critical because nutrients and wastes must pass through the cell's surface. The ratio explains why cells have specific shapes and why organelles like mitochondria have folded internal structures—to maximize surface area.
The specialized shapes of cellular structures aren't random. The folds inside mitochondria and the flat, pancake-like structures in chloroplasts provide greater surface area for chemical reactions to occur. This design principle helps cells function efficiently at their microscopic scale.
🔍 Think about it: If you were to design a cell, how would you maximize its surface area while maintaining a practical volume? Nature has already solved this problem through evolution!
Prokaryotic Cell Structure
Prokaryotic cells are always unicellular organisms with simpler structures than eukaryotic cells. They contain a single circular chromosome (not enclosed in a nuclear membrane), ribosomes for protein synthesis, and cytoplasm. While they lack membrane-bound organelles, they do have specialized internal regions for specific functions.
Prokaryotes come in three basic shapes that relate to their functions and environments. Cocci are round bacteria, bacilli are rod-shaped, and helical bacteria have spiral forms. These shapes influence how the bacteria move, attach to surfaces, and resist environmental pressures.
The cell wall is a crucial protective structure in prokaryotes that prevents them from bursting in watery environments. In bacteria, this wall is made primarily of peptidoglycan—a combination of proteins and complex carbohydrates. Bacteria can be classified as either Gram-positive or Gram-negative based on their cell wall structure.
🧪 Gram staining is a key laboratory technique: Gram-positive bacteria have thick peptidoglycan layers and stain blue, while Gram-negative bacteria have thin peptidoglycan layers between phospholipid layers and stain red. This difference affects which antibiotics work against them!
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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
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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.
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
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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
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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
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
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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
Understanding Cells: Key Study Notes
Cells are the fundamental units of life, where individual parts work together to create living systems. Understanding cell structure and function is essential to grasping how all living things operate, from the simplest bacteria to complex organisms like humans.
Understanding Cell Basics
Cells are the basic units of life that demonstrate emergent properties—individual organelles can't sustain life alone, but when organized within a cell membrane, they create living systems. These microscopic structures are the foundation of all living organisms.
There are two primary types of cells: prokaryotic and eukaryotic. Prokaryotic cells (including bacteria and archaea) evolved first, about 3.5 billion years ago. They lack a nucleus and membrane-bound organelles, though they do contain ribosomes. The oldest fossil evidence of these ancient cells can be found in stromatolites in Shark Bay, Australia.
Eukaryotic cells developed later and feature a membrane-bound nucleus and organelles. All organisms except bacteria and archaea are composed of eukaryotic cells. They're generally larger and more complex than their prokaryotic counterparts.
💡 The Endosymbiotic Hypothesis explains how eukaryotic cells evolved: smaller prokaryotes began living inside larger ones in mutually beneficial relationships. Over time, these smaller organisms evolved into organelles like mitochondria and chloroplasts.
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Evidence for Endosymbiosis & Cell Dynamics
The evidence supporting the endosymbiotic theory is compelling when we examine mitochondria and chloroplasts. These organelles maintain their own circular chromosomes similar to bacteria, contain bacteria-like ribosomes, and can reproduce independently within eukaryotic cells. Their double phospholipid bilayer membranes suggest they were once free-living organisms that were engulfed.
A crucial concept in cell biology is the surface area-to-volume ratio. As cells grow larger, their surface area increases more slowly than their volume. This ratio is critical because nutrients and wastes must pass through the cell's surface. The ratio explains why cells have specific shapes and why organelles like mitochondria have folded internal structures—to maximize surface area.
The specialized shapes of cellular structures aren't random. The folds inside mitochondria and the flat, pancake-like structures in chloroplasts provide greater surface area for chemical reactions to occur. This design principle helps cells function efficiently at their microscopic scale.
🔍 Think about it: If you were to design a cell, how would you maximize its surface area while maintaining a practical volume? Nature has already solved this problem through evolution!
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Prokaryotic Cell Structure
Prokaryotic cells are always unicellular organisms with simpler structures than eukaryotic cells. They contain a single circular chromosome (not enclosed in a nuclear membrane), ribosomes for protein synthesis, and cytoplasm. While they lack membrane-bound organelles, they do have specialized internal regions for specific functions.
Prokaryotes come in three basic shapes that relate to their functions and environments. Cocci are round bacteria, bacilli are rod-shaped, and helical bacteria have spiral forms. These shapes influence how the bacteria move, attach to surfaces, and resist environmental pressures.
The cell wall is a crucial protective structure in prokaryotes that prevents them from bursting in watery environments. In bacteria, this wall is made primarily of peptidoglycan—a combination of proteins and complex carbohydrates. Bacteria can be classified as either Gram-positive or Gram-negative based on their cell wall structure.
🧪 Gram staining is a key laboratory technique: Gram-positive bacteria have thick peptidoglycan layers and stain blue, while Gram-negative bacteria have thin peptidoglycan layers between phospholipid layers and stain red. This difference affects which antibiotics work against them!
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 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