Viral life cycle facts for kids
|
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism.
Viruses are incredibly small, much smaller than even the tiniest bacteria. They're so small you can't see them with a regular microscope – you need a powerful electron microscope to get a good look!
Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
How small are they?
To measure viruses, scientists use a unit called a nanometer (nm). A nanometer is incredibly small – one billionth of a meter! That's 0.000000001 meters! To put that in perspective, if you lined up one billion nanometers, they would stretch out to be one meter long – that's like stacking one billion tiny LEGO bricks end-to-end to reach one meter!
Think about it: a single grain of sand is about 100,000 nanometers across! A human hair is about 80,000 – 100,000 nanometers wide! Viruses are much, much smaller than that. They typically range in size from around 20 nanometers to 400 nanometers.
What are viruses made of?
Unlike living things like plants and animals, viruses aren't made of cells. They're much simpler. Basically, a virus is a tiny package of genetic material (either DNA or RNA – think of it like a secret code) wrapped up in a protein coat. This protein coat protects the genetic material and helps the virus attach to cells. Some viruses also have a membrane surrounding the protein coat, kind of like an extra layer of protection. Imagine a tiny, hard candy shell containing a special message. That's sort of what a virus is like!
How do viruses work?
Viruses can only reproduce (make copies of themselves) inside the cells of a living organism, like plants, animals, or even bacteria. They can't reproduce on their own; they need to hijack a cell's machinery to do the job for them.
Here's how it usually works:
1. Attachment: The virus attaches itself to a cell. Think of it like a key fitting into a lock. Each virus has a specific type of "key" that only fits certain types of "locks" (cells). That's why some viruses infect only certain plants or animals.
2. Entry: Once attached, the virus enters the cell. It might inject its genetic material into the cell or it might be engulfed by the cell.
3. Replication: Inside the cell, the virus uses the cell's machinery to make copies of its genetic material and protein coat. It's like taking over a factory to produce more of itself!
4. Assembly: The newly made genetic material and protein coats assemble into new viruses.
5. Shedding: The new viruses burst out of the cell, ready to infect more cells. This is called shedding and is the final stage in the viral life cycle. Sometimes the cell is destroyed in the process; sometimes it survives, but it’s weakened.
6. Latency: Some viruses can "hide" within a cell, which may mean that they evade the host cell defenses or immune system and may increase the long-term "success" of the virus. This hiding is deemed latency. During this time, the virus does not produce any progeny, it remains inactive until external stimuli—such as light or stress—prompts it to activate.
