These two articles in the New York Times will give you a decent understanding of how the Covid-19 virus works and what it looks like. The first, by Jonathan Corum (the NYT’s graphics editor) and science journalist Carl Zimmer, explains how the virus’s genome is put together and shows a 3-D reconstruction of the 29 proteins it makes.
Covid-19 is an RNA virus, meaning that its genetic material isn’t DNA but RNA. It injects its RNA into a cell, and that RNA, besides replicating itself, also begins producing proteins that do various things. These include making the virus’s own protein coat, which, when put together with the newly replicated RNA, makes new viruses that then enter other cells using a “spike protein” that latches onto human cells. I won’t go into detail about this, as you can read about it in many places (e.g., here). Click on the screenshot to read the collaborative article:
The viral proteins do these things (among others):
- Slow down the production of the infected cell’s proteins so that it can make more viral protein
- Tag the human cell’s proteins so they persist when they are scheduled for destruction; this may make cells more susceptible to infection
- Make fluid-filled bubbles inside the cell where new viruses are made
- Helps the virus’s RNA replicate itself
- Camouflage the virus’s genes so they don’t get detected and destroyed by our bodies
- Detect and remove errors (mutations) that occur when the virus’s RNA replicates itself inside the body
- Destroy leftover virus RNA to hide it from the cell’s antiviral defenses.
- Change the internal environment of the cell to make it easier for the virus to replicate
- And, of course, produce the protein coat of the virus. The coat is made of four proteins, including the dreaded “spike protein” that targets a human protein, ACE2, on cell surfaces in the our airway. As the link above explains:
The cells that SARS-CoV-2 prefers to infect have a protein called ACE2 on the outside that is important for regulating blood pressure.
The infection begins when the long spike proteins that protrude from the virus particle latch on to the cell’s ACE2 protein. From that point, the spike transforms, unfolding and refolding itself using coiled spring-like parts that start out buried at the core of the spike.
The reconfigured spike hooks into the cell and crashes the virus particle and cell together. This forms a channel where the string of viral genetic material can snake its way into the unsuspecting cell.
Here’s a 3-D reconstruction from the NYT article showing the virus’s spike protein, in red, latching onto human ACE2 (yellow)
Note that all these functions evolved by natural selection to propagate the virus’s genome. Everything can be understood as ways to facilitate the reproduction of the virus and then to pass it on to other cells and then to other humans. It’s not to the human’s advantage, of course, but to the virus’s. It’s a pathogen—an intracellular parasite that hijacks the cell’s machinery to make more of itself.
Now most biologists wouldn’t consider viruses to be “alive” in the sense that they are not autonomous organisms with both a way to replicate and to metabolize. This, of course, depends on your definition of “life,” and most biologists don’t worry too much about that. What’s important for evolution—and for those wanting to understand Covid-19 or any virus—is that it has a way of replicating itself, even if it has to use another organism to do so. Once it’s a replicator, and has a heredity material, then it can evolve by natural selection, undergoing mutation and accumulating those mutations that facilitate its survival, replication, and transmission.
The article below tells you how the familiar picture of the coronavirus was put together. The red bits on the surface are those spike proteins that latch onto human cells.