Why viruses are alive explain

Viruses have also evolved in such a way that they are difficult to kill. What makes them, including the coronavirus, so tricky to cure? Part of the problem is the nature of viruses themselves. They exist like freeloading zombies — not quite dead, yet certainly not alive.

The odd makeup of these infectious agents is part of what makes them difficult to defeat. Compared to other pathogens, such as bacteria, viruses are minuscule. And because they have none of the hallmarks of living things — a metabolism or the ability to reproduce on their own, for example — they are harder to target with drugs.

Full coverage of the coronavirus outbreak. Antibiotics, which are used to fight bacterial infections, attack the bacteria's cell walls, block protein production and stop bacteria from reproducing.

But they aren't effective against viral infections, because viruses don't carry out any of those processes on their own. Rather, viruses need to invade and take over host cells to replicate. But a virus can't break into just any cell in the body. Instead, one of its proteins will bind to another protein — akin to a key fitting into a lock — which then allows the virus to hijack certain cells.

With this outbreak, the coronavirus' so-called spike protein primarily fits "locks" that are present on lung cells, which is why COVID, the disease it causes, is mainly a respiratory illness. Once the invasion takes place, the cell in essence is transformed into a factory that churns out hundreds and hundreds of copies of the virus, based on instructions encoded in its genetic material — RNA, or ribonucleic acid, in the case of the coronavirus.

The human body has evolved defense systems to protect against these kinds of infections. They do not have cells. They cannot reproduce independently. A coronavirus, for example, is a nanoscale sphere made up of genes wrapped in a fatty coat and bedecked in spike proteins. Still, viruses have many traits of living things. They are made of the same building blocks. They replicate and evolve. Once inside a cell, viruses engineer their environment to suit their needs — constructing organelles and dictating which genes and proteins the cell makes.

Recently discovered giant viruses — which rival the size of some bacteria — have been found to contain genes for proteins used in metabolism, raising the possibility that some viruses might metabolize. Plus, almost every rule that excludes viruses from the land of the living has its own exceptions. For example, Rickettsia bacteria are classified as living but, like viruses, can multiply only within other cells. All living things, in fact, rely on other living things.

A single rabbit cannot replicate on its own, but a rabbit is definitely alive, right? For these reasons and others, the debate over whether viruses are alive or not continues today. In , virologists Marc H. Or maybe a virus can be both nonliving and alive. In , biologist Patrick Forterre of the Pasteur Institute in Paris argued that viruses alternate between an inactive state outside a cell and a living, metabolically active state inside a cell that he calls the virocell.

For Forterre, viruses are like seeds or spores. They have the potential for action and that potential can be extinguished. While debates over classification can at times feel frivolous, in reality how we talk about viruses affects how they are researched, treated and eradicated.

Personifying viruses as villains and menaces interferes with a real understanding of evolution and nature, says Colin Hill , an infectious disease specialist at University College Cork in Ireland. Like that dirt, some scientists consider persistent viral infections as simply a nuisance and therefore not urgent to study.

But one thing that scientists have struggled to agree on is whether or not viruses are alive. After all, they can't survive or replicate without a host cell, and due to their rapidly changing genes, scientists have never been able to work out how or when they evolved. Now a study by researchers in the US has managed to complete the first viral tree of life, and it suggests that not only are viruses alive, they're also really, really old, and they share a long evolutionary history with cells.

The confusion about viruses is a result of their unique life cycle. Specifically the fact that they can't metabolise nutrients, and they don't contain the proteins needed to copy their own DNA and RNA - instead they invade other animals' cells and use their equipment to do it for them.

This has led some scientists to argue that viruses are merely non-living strands of DNA and RNA taken from other cells, enclosed in a neat little protein envelope.