WHAT IS A VIRUS?
Have you ever heard the word “virus?” What is a virus? Some common viruses you
are probably familiar with (and may have even been infected by) are chicken pox,
the common cold, measles, and mumps. A virus does not belong to any of the five
kingdoms of life. Even more odd, a virus is not made up of cells. Viruses do not
eat, they do not produce waste, nor do they do many of the functions that other
living things do. In fact, the only thing they can do is reproduce.
Because viruses do not do many of the functions common among living things,
many scientists do not consider a virus to be a living thing at all. Are viruses alive?
This is a very difficult question to answer. On the one hand, a virus is not made up
of cells, does not eat, nor does it do most of the functions we think of when talking
about living things. So a virus must not be alive, right? Well, wait a minute. A
virus can reproduce. Non-living things cannot reproduce, so a virus must be alive,
right? You can see why scientists are still debating whether or not a virus is a
living thing.
A virus consists of two basic parts. Like a cell, a virus has an outside protective
wall or protein coat called a capsid. This protein coat is very strong that can
protect the virus against harsh environments for many years. This protective shell
makes it very difficult to “kill” a virus. Some viruses have another protective layer
called an envelope.
Inside of this protein coat, the virus is filled with bits of nucleic acids called DNA or
RNA. This DNA is used by the virus to reproduce. A virus cannot reproduce on its
own, it needs to enlist the help of a cell. To reproduce, a virus releases its DNA
into a cell. Remember that DNA in a cell's nucleus is what directs the activities of
the cell. By releasing DNA into the cell, the virus is able to take control of the cell.
Instead of performing its normal functions, the cell begins to do only one thing,
create new viruses.
Through this process, the cell becomes a parent to a new generation of viruses.
The cell is helping to create an enemy that will attack other cells. Eventually the
cell bursts, releasing the newly created viruses. These viruses will then attack
other cells, repeating the process.
The effects of a viral infection can be mild, including a runny nose and red eyes, or
can be extreme, including swollen organs, and even death.
Follow Up Questions:
1. What biomolecules are viruses made from?
2. There is a debate on whether or not viruses are living organisms. What are
the characteristics that make it living? What are the characteristics that
make it nonliving?
Using the structure below, answer the questions that follow.
3. Which structure could possibly be made of nucleic acid?
4. Which structure is found outside the cell after the cell is infected?
5. What is structure 1 made up of?