How do cells work?

Harleen Saini
23 February 2018

Above: Image © jklr,

Sometimes, in everyday life, we don’t stop to think about how or why our bodies do certain things. For example, have you ever wondered how a cut on your arm heals? When you first get the injury, you notice bleeding. You may quickly apply some ointment and then a Band-Aid. After a few days, the cut has mostly healed and may have even left a scar.

Now, this process of healing is actually quite complex. What is important to note, however, is that it involves many cells and proteins. So what exactly are cells, and how do they work?

Did you know? The process of healing for minor skin injuries, such as a cut, is called regeneration. The body removes the damaged cells over the injury area and replaces these with fresh new cells.

What are cells?

Cells are what make up all organisms: eukaryotes (like humans) and prokaryotes (like bacteria). They are critical for all the things an organism needs to do in a day, like make energy, remove toxins, and even make proteins. In other words, cells are a big deal. In fact, humans are made up of trillions of cells. Neither you nor I nor any living thing around us would exist without them!

Cells are made up of many different structures called organelles. Each organelle has a specific function and makes sure the cell is able to work properly. Just like our bodies have organs with specific functions, cells have organelles. In other words, organelles are the “organs” of cells.

Today, we will focus on five major organelles: nucleus, endoplasmic reticulum, Golgi complex, lysosomes, and the mitochondria.

Part of a Cell
Above: Image © Part of a Cell.
Image modified from Wikimedia Commons by Harleen Saini.

The Nucleus (the Control Centre)

The nucleus1 is often considered the most important organelle. It’s found only in the cells of eukaryotes (animals and plants). This is where the cell’s DNA lives.

The DNA is sort of like the blueprints for the cell’s functions. It tells the cell to do what it needs to do! DNA is important for making proteins . You’ll read more about these shortly.

DNA is also the main genetic component of the cell. It is important for determining your traits, such as your eye color and height, and much more. That’s why scientists like me like to think of the nucleus as the “control centre” of the cell.

Did you know? Prokaryotes (single-celled organisms) don’t have nuclei!

The Endoplasmic Reticulum (The Workshop)

There are two types of endoplasmic reticulum (ER), and each has its own functions.

The rough ER 2 is covered in little protein granules called ribosomes. You could even think of these as little pimples on the surface of this organelle. (Gross, I know!) The main functions of the rough ER are to make proteins and make sure they work right. The rough ER makes proteins using the information in your DNA.

Proteins can have different functions. Some are important for certain parts of the body. For example, the protein keratin makes your hair and nails strong. Others are important for speeding up chemical reactions that happen in the body. These are called enzymes.

Did you know? In cases where the rough ER doesn’t work, you can get conditions such as a certain type of emphysema, a critical lung condition that can make it difficult to breathe even with simple activities such as walking.

The smooth ER3is literally what it sounds like. These little guys don’t have any ribosomes on them and have a nice, smooth surface. Their main function is to detox the cell. This means they help clean the cell of things such as toxins like alcohol or left-over compounds that the cell no longer needs. Without the smooth ER, the cell could die from the poisonous after-effects of these compounds. You can sort of think of the smooth ER as “cleansing” the cell, just as you do when you wash your hands after getting bike oil on them.

Did you know? The smooth endoplasmic reticulum is most abundant in organs such as the liver and kidneys. This is why the kidneys and liver are best at detoxifying your body of toxic compounds.

The Golgi Complex (the Post Office)

The Golgi complex (or Golgi apparatus)4 receives freshly-made proteins from the rough ER and adds the final touches to them. It then ships out the proteins in vesicles5 (little bubble-like vehicles that transport the proteins) to their destination so they can do what they need to do. Imagine you want to send a video game to your friend who lives in a different country. You wrap it nicely and then take it to the post office. There, they add your friend’s address tag and then ship it off. This is similar to how the Golgi complex works. That’s why we scientists like to call this the “post office” of the cell.

Lysosomes (the Recycling Trucks)

Lysosomes6 are made by the Golgi complex and are important for destroying compounds or smaller organelles that are no longer working correctly. The lysosomes help destroy and recycle these to be used somewhere else. They can destroy older organelles to use their nutrients for other cellular functions and needs.

The Mitochondria (the Powerhouse of the cell)

Lastly, the mitochondria7 are often called the “powerhouse” of the cell. But this organelle is also important for other reasons. It helps make ATP, which can then be converted to energy after a chain of biochemical processes. ATP is actually a chemical molecule that can be converted into energy through a biochemical process called hydrolysis. This process can be complicated, but in simple words, when water and ATP go through a chemical reaction, energy is released. You can then use this energy for activities such as running...or for taking that biology test on cells!

Did you know? Mitochondria are most abundant in the cells of the heart. That’s because the heart needs the most ATP and energy conversion. This is what helps the heart constantly beat without rest!

Summing up...

Okay, so now you know a little more about cells and organelles. Let’s try to summarize the information with the example we started with.

Let’s say you were riding your skateboard and then you fell, getting the cut on your arm. Where did your muscles get the energy to ride on the skateboard in the first place? From the ATP found in the mitochondria.

Now, after a few days your cut heals, leaving a scab. Remember how I had said there are many proteins involved with this? Well, those proteins originally started from DNA, which is found in the nucleus.

After a series of reactions, the ribosomes on the rough ER helped make proteins. These proteins were then packed into vesicles (“vehicles”) that took the proteins to the Golgi Complex for the final touches. The finished proteins were then told to go to where your cut was, and helped form the scab.

During that process, the smooth ER and lysosomes may have been doing their duties as well, although they were not exactly involved in the scab formation. Also, realize that all of this is a joint effort of many cells working together, not just one!

So the next time you have to take a test on cells and organelles, remember, you’ve learned about some pretty awesome stuff!

Learn More!

Biology: Cell Structure (2015)
Nucleus Medical Media

Eukaryopolis: The City of Animal Cells (2012)
Crash Course

Learn About Organelles (2017)
Thought Co


Eukaryotic Cells possess a Nucleus and Membrane-Bound Organelles (2014)
Scitable by Nature Education

Endoplasmic Reticulum (Rough and Smooth) (2015)
British Society for Cell Biology

Organelles of the Eukaryotic Cell (2000)
Molecular Cell Biology: 4th edition

Anatomy and Physiology: The Unity of Form and Function (2012)

What Are Mitochondria? (2014)
HeartMD Institute

How Cells Work: Enzymes (2000)
How Stuff Works.

Structure and Functions of kertain proteins in simple, stratified, keratinized and cornified epithelia (2009)
Journal of Anatomy

Prokaryotic Cells (2016)
Khan Academy

Adenosine Triphosphate - ATP (n.d.) Bristol University

Harleen Saini

Hello everyone! I am a premedical student from the United States who is hoping to become a physician one day. My love for science began with watching shows such as Bill Nye the Science Guy and The Magic School Bus series. These helped make science fun and exciting, and eventually led me to pursue an undergraduate degree in Biological Sciences which I completed in 2016. I enjoy being able to share my passion for STEM topics, especially health science and biology, and hope to help others fall in love with the sciences as well. Outside of this, I am also a musician, enjoy dancing and love to learn foreign languages!

b i u quote

Save Comment