Did you know that The Adventures of Mrs Ribozome is based on life within a human cell? But what is a cell, and what’s inside it? These are great questions! Read on to discover the wonderful world of cell biology.
An introduction to organisms, cells and organelles
Biology is what it’s called when we look at life and living organisms.
In biology, an organism is a living plant, animal, or any other living thing. So, you are an organism, and so are the animals and plants in your backyard. There are even some organisms that we can’t see with the naked eye, such as bacteria and yeast. All of these are organisms, as they are living things.
For now, let’s focus on humans. If we looked inside the human body, we would see things like bones, muscles, and organs (for example, the heart, the brain, and the stomach). But what if we zoomed in further? When we zoom in really far, we can see that there are small building blocks. These are so small, that in real life, they can only be seen with a microscope! These building blocks are called cells.
Because cells are the building blocks of an organism, cells are known as the basic unit of life. In fact, all organisms are made up of one or more cells. Humans are made up of trillions of cells! But not all of these cells are the same. There are skin cells, muscle cells, brain cells, blood cells, and many more different types of cells.
Organelles featured in the book
Inside a human cell, there are organelles, which are like mini buildings or factories within the cell. With many factories in real life, one factory makes one main type of product; for example, a paper factory makes paper, and a biscuit factory makes biscuits. This is the same inside cells – different organelles are just like different factories, and they do extraordinary things! Let’s take a closer look at some of the organelles found in a usual human cell.
The Nucleus
The nucleus is a massive library, and its books are called deoxyribonucleic acid, or DNA, for short. DNA holds the genetic information that helps to make you, you!
Half of the DNA in the nucleus of your cells is from your biological mother, and the other half from your biological father. The information held within DNA is determined by the DNA bases: Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). So, DNA is like a very long book made up only of the four letters A, T, G and C.
Just like a book in real life, DNA can be read, and the information within DNA can be used to make other important cell components. When this happens, DNA is used to make RNA, or ribonucleic acid. From there, the RNA can be used to make proteins – we’ll talk more about proteins soon.
When there are issues in or around a town, often the town hall will react and provide help. In the cell, the nucleus is also like the town hall, as it responds to events inside or outside of the cell. Changes within the nucleus can decide on what parts of the DNA can be read and therefore, what cell components are made.
Ribosomes and the Endoplasmic Reticulum
The information within DNA can be used to make cell components such as proteins. If the cell is a town, then proteins are one of the main building materials used to build the town; they can be used to provide structure to the buildings, or they can act as machines and engines that help the town work efficiently.
Ribosomes are the smallest organelle in the cell, but don’t be fooled by their size, as they have a very important role – they make proteins! Proteins can be made by ribosomes that are floating around in the cell, or by ribosomes that are attached to the endoplasmic reticulum (ER).
When ribosomes are attached to the ER, it appears ‘rough’ under the microscope, and so it is called the rough endoplasmic reticulum. The rough ER has many roles, such as to get proteins ready for their final destination, and to help transport them to different parts of the cell.
When no ribosomes are attached to the ER, the ER appears ‘smooth’ and it is called smooth endoplasmic reticulum. One important role of the smooth ER is to make products such as fats and some hormones.
Mitochondria
The mitochondria are commonly known as the ‘powerhouse’, or the energy factory of the cell, as they produce most of the cell’s energy.
Remember that the nucleus has a big DNA library? Well, mitochondria have their own little libraries, filled with mitochondrial DNA. However, the DNA in the mitochondria is a bit different to the DNA in the nucleus; for example, mitochondrial DNA forms a circle. Also, humans get all of their mitochondrial DNA from their biological mother – sorry, Dad!
Lysosomes
Lysosomes can be thought of as the cell’s digestive system. If there are contents that need to be degraded, the lysosome is often involved. The inside of a lysosome is a harsh, acidic environment, with many special proteins that can chew and destroy material. If there are bacteria or viruses that enter the cell, they can eventually be destroyed inside the lysosomes. However, some bacteria and viruses are capable of escaping before they are destroyed.
Other Organelles
Although we have only talked about a few organelles here, there are many more organelles that call the cell their home.
One organelle not previously mentioned is the Golgi apparatus. The Golgi apparatus receives proteins and fats from the ER, and then can ‘decorate’ and change them before sending them to other parts of the cell.
We must also mention the cell membrane and the cytosol. The cell membrane is like the fence that surrounds the town. It keeps all of the contents of the cell inside and provides gateways for things to enter. Inside the cell, the organelles float in a watery soup called the cytosol.
You can discover more about cells and organelles from sources in the Further Reading section of this page.
A viral infection
Viruses are tiny, infectious particles. They do not contain the components needed to make more of themselves – no nucleus, no ribosomes, or other organelles. Because of this, they must invade a living cell and use the cell’s components in order to replicate.
Viruses are very simple, usually containing genetic material (DNA or RNA) that is covered in a protein coat. There are viruses that can infect all types of cells – human cells, other animal cells, and plant cells. There are even viruses that only infect bacteria.
When a human cell is infected by a virus, the immune system will be activated, and will work to clear the infection. Your immune system is always learning, and always working hard to protect you from nasty bacteria and viruses!
Further reading
Want to learn more about cells? Check out the free resources below.
And kids - make sure that an adult is learning alongside you, too!
The Essentials of Cell Biology is an online eBook available at Scitable. It is an excellent resource designed for absolute beginners of all ages.
Rader's Biology for Kids has lots of information about biology and cells. Start off with the topics on cell structure and function.
The Ask A Biologist site by Arizona State University is another great resource. Here, you'll find information on cells, as well as a Virtual Cell Viewer, puzzles, and worksheets.