Brain BREAK! presents: Viruses.
Viruses are NOT alive. They don’t have their own metabolism, reproduction, etc. without a host cell. They’re sacks of DNA or RNA.
A human cell scolds a tiny virus: “Get a job!”
Looking at the basic anatomy of a very plain virus:
- Genetic material: single-stranded or double-stranded RNA or DNA (there is also a positive or negative trait, but we’ll skip that for now).
- Capsid: proteins that protect RNA or DNA (it tends to have sort of a crystalline structure).
- Envelope (optional): it’s “borrowed” from a host cell – those antigens are a great disguise!
They vary a lot. Keep in mind that some have very bizarre shapes. Rabies, for example, weaves its RNA into a spiral shape and has a appears as something of a bullet, unlike the typical spherical virus you’ll see illustrated in headlines.
(I’m trying hard not to make the viruses talk because they’re not life.)
Moving on to bacteriophages, which tend to have a “needle” for injecting its genetic material into bacteria, with “legs” for attachment and the capsid on top. A concerned bacteria frets, saying “But I’m scared of needles!”
On to different cycles of viruses.
- Lytic. The viruses wastes no time, drives a cell to work itself for the viruses’ benefit, and then lyses the host cell, killing it.
- Lysogenic. Embeds itself in the host’s DNA – hence “genic” – and “waits” to enter a lytic cycle. Or it might never!
And remember how easily bacteria share their genetic material?
In an example of a lytic virus, a nerve cell looks on as a spray of Rhabdovirus bursts out of the cytoplasm. It frowns, muttering, “Well, that’s going to leave a mark.”
In an example of a lysogenic virus, two bacteria casually converse. One says, “There’s something different about you.” The other says, “Well, I did get a new haircut.” Meanwhile, a bacteriophage virus has injected its DNA in this unfortunate soul; this segment appears interwoven with the nucleoid. Another virus floats away, laughing, “MWA HA HA!”, seeing that a bacteria has been infected. A ticking time bomb.
(I give up. A virus talked. Oh, well.)
Like anything in biology, form and function are connected. You can learn a lot about a virus from its form.
Here’s a fun game: correct your friends when they say a disinfectant “kills viruses.” (That’s gonna lyse a lot of friendships.) -CNx