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Aishani
12/13/2025
Biology
Introduction to Cells: Basic Units of Life
15
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Dec 13, 2025
•
The Basics of Cells: Exploring Life's Building Blocks
Aishani
@shani_09
1 / 4
Introduction to Cells
Cells are incredibly organized structures made of molecules that serve as the basic unit of life. Every living organism is composed of at least one cell, and they come in two main types: prokaryotic and eukaryotic.
Prokaryotic cells are generally smaller and simpler. The term "pro" means before and "kary" means nucleus, indicating they lack a true nucleus. These single-celled organisms don't enclose their DNA in a nucleus - instead, their DNA is found in an area called the nucleoid. They range from 0.1 to 5.0 micrometers in size and belong to two domains: Bacteria and Archaea.
Eukaryotic cells are larger and more complex than prokaryotic cells. They can be either unicellular or multicellular. A key difference is that prokaryotic cells have a single open space with no internal membranes, while eukaryotic cells contain specialized compartments.
💡 Think of a prokaryotic cell like a studio apartment (one open space) and a eukaryotic cell like a house with many rooms (specialized compartments).
Eukaryotic Cells
Eukaryotic cells make up all multicellular organisms, including plants, animals, and fungi. Unlike prokaryotic cells, they have a nucleus that houses linear chromosomes and multiple membrane-bound organelles that perform specialized functions.
These cells are significantly larger than prokaryotic cells, typically measuring 10 to 100 micrometers. Their compartmentalized structure allows each section to maintain its own unique environment. This organization enables eukaryotic cells to carry out complex metabolic reactions that wouldn't be possible in prokaryotic cells.
The ability to maintain different conditions in different parts of the cell is one of the main reasons why eukaryotic cells can grow larger than prokaryotic cells. Each organelle works like a specialized factory, focusing on specific cellular tasks.
🔍 The compartmentalization in eukaryotic cells is like having different rooms in a house with different conditions - the kitchen is warm for cooking while the refrigerator keeps food cold.
Discovery of Cells
The journey to understanding cells began in the 1500s when eyeglass makers discovered that combining several lenses allowed them to see small objects more clearly. These early discoveries eventually led to the development of microscopes.
In 1665, Robert Hooke made a groundbreaking discovery when he used an early compound microscope to examine a thin slice of cork. He observed tiny compartments that reminded him of small rooms, which he called "cells". Later in 1670, Anton van Leeuwenhoek used a single-lens microscope to observe pond water and discovered a world of tiny living organisms that we now recognize as prokaryotes.
These discoveries laid the foundation for the Cell Theory, which developed through the work of several scientists. Matthias Schleiden (1838) concluded that all plants are made of cells, while Theodor Schwann (1839) extended this to include animals. In 1855, Rudolph Virchow added that new cells can only come from pre-existing cells.
⚡ Imagine the excitement these scientists must have felt seeing an entirely invisible world for the first time - it would be like discovering aliens living in your backyard!
The Cell Theory
The Cell Theory represents one of the most fundamental concepts in biology. This theory emerged from the collective work of several scientists over many years and consists of three main principles.
First, all living things are made of cells. Whether it's a tiny bacterium or a massive blue whale, cells form the foundation of every organism on Earth. Second, cells are the basic units of structure and function in all living things. This means that cells not only make up living organisms but also carry out all the activities necessary for life.
Third, new cells are produced from existing cells through cell division. This principle explains how organisms grow, develop, and repair themselves. It also means there's an unbroken chain of cell division stretching back to the first cells on Earth billions of years ago.
🌟 The Cell Theory connects all living things through a common building block - cells. You're made of the same fundamental units as trees, dogs, and even the bacteria in your yogurt!
We thought you’d never ask...
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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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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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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.
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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
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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
The Basics of Cells: Exploring Life's Building Blocks
Aishani
@shani_09
Cells are the basic building blocks of all living organisms. They come in two main types: prokaryotic and eukaryotic, each with distinct features that affect their function and complexity. Understanding cells helps us understand how life works at its most... Show more
Introduction to Cells
Cells are incredibly organized structures made of molecules that serve as the basic unit of life. Every living organism is composed of at least one cell, and they come in two main types: prokaryotic and eukaryotic.
Prokaryotic cells are generally smaller and simpler. The term "pro" means before and "kary" means nucleus, indicating they lack a true nucleus. These single-celled organisms don't enclose their DNA in a nucleus - instead, their DNA is found in an area called the nucleoid. They range from 0.1 to 5.0 micrometers in size and belong to two domains: Bacteria and Archaea.
Eukaryotic cells are larger and more complex than prokaryotic cells. They can be either unicellular or multicellular. A key difference is that prokaryotic cells have a single open space with no internal membranes, while eukaryotic cells contain specialized compartments.
💡 Think of a prokaryotic cell like a studio apartment (one open space) and a eukaryotic cell like a house with many rooms (specialized compartments).
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Eukaryotic Cells
Eukaryotic cells make up all multicellular organisms, including plants, animals, and fungi. Unlike prokaryotic cells, they have a nucleus that houses linear chromosomes and multiple membrane-bound organelles that perform specialized functions.
These cells are significantly larger than prokaryotic cells, typically measuring 10 to 100 micrometers. Their compartmentalized structure allows each section to maintain its own unique environment. This organization enables eukaryotic cells to carry out complex metabolic reactions that wouldn't be possible in prokaryotic cells.
The ability to maintain different conditions in different parts of the cell is one of the main reasons why eukaryotic cells can grow larger than prokaryotic cells. Each organelle works like a specialized factory, focusing on specific cellular tasks.
🔍 The compartmentalization in eukaryotic cells is like having different rooms in a house with different conditions - the kitchen is warm for cooking while the refrigerator keeps food cold.
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Discovery of Cells
The journey to understanding cells began in the 1500s when eyeglass makers discovered that combining several lenses allowed them to see small objects more clearly. These early discoveries eventually led to the development of microscopes.
In 1665, Robert Hooke made a groundbreaking discovery when he used an early compound microscope to examine a thin slice of cork. He observed tiny compartments that reminded him of small rooms, which he called "cells". Later in 1670, Anton van Leeuwenhoek used a single-lens microscope to observe pond water and discovered a world of tiny living organisms that we now recognize as prokaryotes.
These discoveries laid the foundation for the Cell Theory, which developed through the work of several scientists. Matthias Schleiden (1838) concluded that all plants are made of cells, while Theodor Schwann (1839) extended this to include animals. In 1855, Rudolph Virchow added that new cells can only come from pre-existing cells.
⚡ Imagine the excitement these scientists must have felt seeing an entirely invisible world for the first time - it would be like discovering aliens living in your backyard!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Cell Theory
The Cell Theory represents one of the most fundamental concepts in biology. This theory emerged from the collective work of several scientists over many years and consists of three main principles.
First, all living things are made of cells. Whether it's a tiny bacterium or a massive blue whale, cells form the foundation of every organism on Earth. Second, cells are the basic units of structure and function in all living things. This means that cells not only make up living organisms but also carry out all the activities necessary for life.
Third, new cells are produced from existing cells through cell division. This principle explains how organisms grow, develop, and repair themselves. It also means there's an unbroken chain of cell division stretching back to the first cells on Earth billions of years ago.
🌟 The Cell Theory connects all living things through a common building block - cells. You're made of the same fundamental units as trees, dogs, and even the bacteria in your yogurt!
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