How Viruses Function & Reproduce Will SHOCK You!
Read until the end for a bonus surprise!
Influenza. SARS-CoV-2. Chickenpox. Polio. Rabies. Hepatitis.
These names all have one thing in common: they're viruses!
You've probably heard of the names of these viruses before sometime in your life, but how exactly do they work? What are the red parts sticking out for? How do they reproduce?
In this article, we'll breakdown the characteristics and structures of viruses and explain how it infects our healthy cells.
A virus is a pathogen which can infect healthy living cells within an organism (pathogen - an infectious agent that can cause disease). These healthy living cells are known as host cells.
Host cells can be infected by a virus and serve as a place where the virus can reproduce.
Now, before we get any deeper, we need to understand the structure of a virus and its purpose, as well as its many characteristics.
First, the structure of a virus is rather simple. It's composed of three main components:
Genetic Material (DNA or RNA)
Don't freak out, we'll explain this in just a second.
The genetic material contains the instructions for making the viral proteins and replicating the viral genetic material within the cell.
The capsid is a protein coat. It protects the genetic material in the virus! Think of it as a jacket preventing heat from leaving your body.
Some viruses, not all, may have a lipid envelope, which also is a protective outer coat.
Surface proteins are found on the surface of the viruses. They can serve as antigens to cause the host's immune system to produce antibodies.
Surface proteins are also found in other pathogens as well. Each pathogen has its own unique surface proteins, acting as a "name tag."
Use the model below and see if you can identify the genetic material, capsid, lipid envelope, and antigens!
A - capsid
B - genetic material
C - lipid envelope
D - antigens OR surface proteins
What are the characteristics of viruses?
No metabolism or cellular respiration
Not a cell
Does not maintain homeostasis
Require host cell to reproduce
As mentioned above, viruses are non-living. But, how can they reproduce?
When it comes to viral reproduction, there are two types of viruses: Virulent and Temperate
Virulent viruses are viruses that will attack the host cell and destroy it immediately. These viruses go through the Lytic Cycle.
Unlike virulent viruses, temperate viruses are viruses that will stay dormant, meaning that they will infect the host cell, but will not destroy it immediately. To reproduce, they go through a process known as the Lysogenic Cycle.
Lytic Cycle: Attack and Destroy
At first, this process of viral replication may seem confusing. But, let me give you an analogy or a scenario of how you can remember this process.
Let's say there's a burglar (virus). Let's name this burglar John. He decides to target a house (host cell) in a neighborhood. He finds the right house and decides to approach it (I do not condone burglary and am not encouraging it in any way).
To be extra cautious, John scouts the house. He uses his two hands to attach to the window to peek inside of the house. Once he decides that the house is a perfect target, he makes entry into the house.
John, with his duffel bag, forces the owner to take out all of his valuables and hand it over to him (replication). He now has control over the whole house.
He then takes the valuables and stuffs them into a duffel bag so they can be held in one place (assembly).
On his way out of the house, John ransacks nearly everything in the owner's house. Seeing nothing he likes, he escapes the crime scene, leaving everything in shambles (Release & Lysis).
Attachment - the virus will attach itself to the host cell. The protein capsid will attach to the receptors (proteins on the host cells) on the host cell.
Entry - the virus will inject its genetic material into the host cell.
Replication - the virus dominates the host cell, forcing it to make new viral nucleic acid and proteins.
Assembly - new viruses are put together to form new viruses.
Release & Lysis - new viruses will rupture the host cell, releasing viruses to infect other cells.
Lysogenic Cycle: Infects Cells, Doesn't Destroy Immediately
Have you ever watched a Mission Impossible film, or any action and spy movie?
Well, then you're probably familiar that every time the main character needs to escape, he or she will need a disguise to blend in to the general crowd and avoid being caught.
You see, the lysogenic and lytic cycle are nearly similar.
However, instead of forcing the host cell to make new viral nucleic acid and proteins, the viral genetic material blends in with the host cell DNA, forming a prophage.
Attachment & Entry- the virus will attach itself to the host cell and inject itself into the host cell.
Development of the Prophage- the host cell DNA and viral DNA will combine together forming a prophage.
Replication - viral DNA will be replicated; it will not harm the host cell YET.
Keep in mind that viruses may go back to the lytic cycle due to external conditions (UV radiation & X-Rays)
With that being said, the concept of viruses wasn't as hard as you thought right? If you remember the analogies I gave you earlier in the article, it shouldn't be too difficult to understand!
🎁 Surprise Bonus: You can book a FREE CLASS with me for Biology on the "Tutoring" section of my website to learn more! In the course, I'll provide you with lifetime access to my practice tests, worksheets, and lesson curriculum, and ultimately prepare you for success!