A virus is a microscopic biological assembly of molecules that infect other cells and replicates within them. A virus can infect all kinds of organisms and can cause fatal diseases such as Ebola and Dengue fever. While viruses contain DNA, scientists do not believe them to be “living.”
All viruses have particular characteristics that classify them as a virus. For instance, all viruses have DNA or RNA that contains their genetic information. This is akin to the DNA that living organisms have.
A Virus keeps its DNA or RNA in a shielded casing known as the capsid. The capsid is composed of unique proteins that provide protection to the virus. Some viruses may also contain a membrane layer known as the envelope.
While all viruses share some common characteristics, there are many different types of viruses. Some viruses infect animals and humans, while others infect bacteria.
Virus and Humans
It is crucial for scientists to study viruses as they are capable of causing harm to humans. If a person becomes sick from a virus, it’s said to be a viral infection. For instance, anyone with a cold probably has a viral infection.
There are several types of viruses that can cause sickness and some cause more harm than others. While a cold may go away in a few days, other viral infections, such as Ebola, chicken pox, polio, and AIDS, can’t be simply cured.
Scientists have discovered ways to create vaccines for many such viral infections. One example would be the polio vaccine, where doctors can now ensure that a person never gets infected by the polio virus.
Is Virus Alive?
Viruses do exhibit some features of living things. However, they do not have all of them. In fact, they are not considered as “alive.” There are 7 features that scientists list to consider something as living.
7 Characteristics of Life
Living things sustain homeostasis. This means that organisms can adjust their inner environment, and they achieve it no matter what the environment is like. For instance, living organisms can control their internal temperature.
An organism should be able to reproduce to be living.
A living organism must be organized further into smaller units called cells.
- Response to Environment
Living things can respond to its environment.
- Use Energy
Living things should be able to utilize energy via metabolism.
An organism should be able to grow and mature. Multiple-celled organisms grow by producing more cells, while single-celled organisms grow larger in size.
Living organisms tend to evolve over time by passing on their characteristics to their offspring.
The Virus Question – Are Viruses Alive?
The question of whether viruses are alive is hard for scientists to answer definitively. Scientists agree that viruses have a few of the characteristics of life. For instance, a virus is able to respond to its environment.
But, there are other characteristics that viruses lack. For instance, viruses do not grow. Also, they cannot reproduce by themselves, unless inside of a host cell.
For other characteristics of life, it is unclear if viruses have those or not. For instance, there is a dispute about whether viruses maintain homeostasis. But, overall scientists agree that viruses are not living.
Viruses are tiny particles that can infect humans, animals, and even plants. One can find them almost everywhere; from washrooms to schools to workplaces and even inside volcanoes. Here we take a closer look at viruses and their structures.
Function of Viruses
A virus works by gaining entry into a host cell and infecting it. It then begins to create more duplicates of it, usually killing the host cell during the process. Essentially, a virus turns regular cells into a factory, and the cycle can go on forever.
Human bodies are capable of fighting off viruses via the immune system and antibodies. This is why we usually stay healthy despite numerous threats that around us. But, if viruses do successfully penetrate our defenses, we might fall sick for some time.
Structure of viruses
A virus needs to take over a host cell in order to reproduce and is not able to do so on its own. This is it is not considered to be living. Viruses are mainly molecules containing nucleic acid and protein. All viruses have a singular purpose: take over host cells and reproduce without stopping.
A typical composure of a virus is:
- A protective shell called the capsid.
- A strand of nucleic acid or DNA located inside the capsid
- A membrane surrounding the virus (may be absent in some viruses)
How Do Viruses Reproduce?
All living things reproduce, but viruses are not alive. So instead, they have a different process known as viral replication. This is when a virus takes control of a cell to create duplicates of itself.
We know that viruses somehow replicate since they’re everywhere. This might seem pretty scary as viruses can make people sick.
Most viruses are in fact quite different. They only affect particular kinds of cells, and only in particular creatures. For instance, rhinovirus only infects respiratory cells in humans. While Bluetongue Virus only infects the tongues of sheep. So, all viruses are very specific in their function.
Viruses vs. Cells
Gaining Access to the Cell
When a virus finds the right cell, it can’t just penetrate it as cells contain a protective membrane and to block them out. But viruses are tricky. They don’t always have to enter the cell. Actually, they just need to place their DNA or RNA into it. A virus contains the DNA or RNA as a plan to create more viruses.
The virus attempts to trick cells into accepting these plans. Usually, it begins with the virus positioning itself on a cell. Then, it inserts its DNA or RNA into the cell.
Directing the Cell
After the initial stage, several things occur. Firstly, the virus itself is rendered useless. This is because a virus injects only once. Yet, its DNA or RNA is sufficient for duplication process. Cells have tiny organelles known as ribosomes that will use the DNA or RNA to duplicate the original virus.
RNA is able to be directly read by ribosomes to create viruses. But DNA has to enter the nucleus first in order to be turned into RNA. Eventually, both DNA and RNA will be put through ribosomes to make new copies.
There are two different methods that viruses can exit from a cell.
- When virus reproduces large amount to fill the cell, it will eventually burst. This will let loose thousands of newly born viruses to roam.
- The virus moves through the membrane of a cell to free itself, which is called budding.
The Case of the Cold
Now that we know how viruses reproduce, let’s look at a particular virus, rhinovirus, which cause the common cold.
Rhinovirus’s tropism is human respiratory cells. The rhinovirus locates them easily. In fact, it is the specific tropism of a virus that makes the cold spread so quickly.
Note that it is in fact not the virus that causes sickness, but our immune system. To stop rhinovirus from reproducing, our bodies need to eliminate the infected cells. It doesn’t feel good, but it is the only way to stop the spread of the virus.