Is a virus alive?

[Roman]

I dont think

I know.

 

[Vkothii]

How come fires burn if they aren't alive? How does that work? How does ice form complex structures if it isn't alive?

Fires don't do anything to control what they do, so they don't work, unless as external agents we constrain them and control what they do.
Ice forms complex structures because of external conditions, like temperature and pressure.

Viruses work differently to fires and ice crystals.
How do they work differently though?

 

[Roman]

Viruses don't control what they do, either. They're very predictable, if we know the conditions they're in.

Given a proper cell, they'll infect it. Just as given the proper material, a fire will burn.

And most viruses are highly influenced by environment- the host's immune system, for instance. Without any immunity, an organism will be consumed by the viral particles.

 

[invert_nexus]

Doesn't that conflict with the idea that viruses aren't alive?

No.
Unless you use evolution in your definition of life.
Did you, by any chance, read all of Hercules' post above?

You haven't distinguished between a working virus and a living organism either.

Semantics.
I'm satisfied with the answers given previously in the thread. No need to endlessly repeat the same answer.

A car works because an agent uses it.
So what uses a virus?

I thought you'd use the "A car works because it was built by a living, thinking creature" gambit.
It would be as useless as the gambit you used instead.

How does a retrovirus insert DNA as genes into a host? Or does the cell do this, and if so, why?
I thought retroviruses had copies of reverse transcription enzymes that did this?

Do you really want a biology lesson on the function of retroviruses?
If so, I bet you could talk Hercules into giving you one. This is his field. I'm a bit rusty although if I wished I could go searching through references for a nice synopsis on the subject.

Basically, you've got it. The reverse transcriptase plays a key role in the process and is part of the virus package.

Viruses carry key proteins within themselves. Another reason why free-floating dna wouldn't be very successful.

 

[invert_nexus]

How do they work differently though?

Different chemical processes taking place.

 

[Vkothii]

Your views are that a virus is inanimate.
But a virus invades a cell and hijacks it.

"A virus works differently because of different chemical reactions"...? That says nothing informative.
And don't go suggesting that books need to be read, either. A virus carries enzymes around, enzymes that function?

Enzymes are useless, like cars are?
Asking "does a car work", then claiming that a car is a useless example looks a little strange.

I'm really just trying to understand why people say things like: "viruses aren't living organisms", then describe how they invade cells, insert their genes, and evolve..?
How they appear to work in quite a different way to passive processes, like a fire, or crystallisation.
And the answer appears to be "No"...? I don't believe it,

 

[Roman]

Please define life for us.

 

[Vkothii]

Life is the set of all things that are capable of persistence, via metabolism and reproduction of material that is required to maintain their structure, and also represent that structure (again as structure). The structures are actively maintained and this requires energy.

The chemicals involved are from a specific set - amino acids for example, but also a host of organic chemicals and organometallic compounds. Lipids, amphoteric compounds, variously polar organic chemicals; it's a large list, but not an open one.

The structures are functional. A characteristic of living organisms is that they separate energy-carrying substances and electric charge - compartmentalisation is important, and separation involves membranes, which are porous.
Some of the openings function as active channels, that pump ions against a gradient, using stored energy.

This is possible (the active creation of an energy potential) because of the structures and the way they function and are under the control of the cell. Regulatory mechanisms are important. Lifeforms regulate the flow of free energy in the environment.

But, the answer's still "No", huh?

 

[Roman]

By that definition, definitely. No membranes.

 

[Vkothii]

What about viruses that have membranes? And a kind of respiratory cycle?

 

[Roman]

What about viruses that have membranes? And a kind of respiratory cycle?

Never heard of such a virus. Unless you mean a cell infected by a virus?

 

[invert_nexus]

Your views are that a virus is inanimate.

Someone said viruses don't move?

"A virus works differently because of different chemical reactions"...? That says nothing informative.

What information are you looking for? You asked how viruses work differently than fires and ice crystals. The answer is that they work differently because different chemical processes are taking place.

Were you looking for specifics? You not only want a lesson in virus mechanics but also combustion and crystal formation?

And don't go suggesting that books need to be read, either. A virus carries enzymes around, enzymes that function?

Enzymes are useless, like cars are?
Asking "does a car work", then claiming that a car is a useless example looks a little strange.

This whole bit is a muddled mess.
Going from textbooks to working enzymes to useless cars.
I never said cars were useless. I said your fallacious gambit of saying cars work because they are driven is a useless analogy. It doesn't help you understand viruses in any way. It merely confuses the issue even more.

Yes. Viruses contain enzymes.
These enzymes work.
That is, they do things.
What things?
Many things.
When?
Under the proper conditions.
How?
Because of their chemical properties.
Why?
Because they have to.
Are they useful?
They can be.
Are they alive?
Depends on your definition of life.
Does a definition of life in which a virus is dead or alive make much difference to the study of said virus?
Not really. Perhaps a little bit, conceptually. But the virus still works the same whether you call it alive or not.
What about enzymes? Alive? Dead? Does it matter?
Semantics. And not really important except conceptually.

When you get down to this level of things, life isn't really an important definition. It's a fuzzy boundary and mostly useless.

I'm really just trying to understand why people say things like: "viruses aren't living organisms", then describe how they invade cells, insert their genes, and evolve..?
How they appear to work in quite a different way to passive processes, like a fire, or crystallisation.

Passive, eh?
Viruses don't make decisions. They don't have will. They act according to their chemical makeup.
They operate on the level of enzymes which act according to their chemical makeup which is controlled by the environment in which the chemical reaction is taking place.
Viruses are passive, in that sense.
Thus, no problems.

Life is the set of all things that are capable of persistence, via metabolism and reproduction of material that is required to maintain their structure, and also represent that structure (again as structure). The structures are actively maintained and this requires energy.

The chemicals involved are from a specific set - amino acids for example, but also a host of organic chemicals and organometallic compounds. Lipids, amphoteric compounds, variously polar organic chemicals; it's a large list, but not an open one.

The structures are functional. A characteristic of living organisms is that they separate energy-carrying substances and electric charge - compartmentalisation is important, and separation involves membranes, which are porous.
Some of the openings function as active channels, that pump ions against a gradient, using stored energy.

This is possible (the active creation of an energy potential) because of the structures and the way they function and are under the control of the cell. Regulatory mechanisms are important. Lifeforms regulate the flow of free energy in the environment.

But, the answer's still "No", huh?

Basically, you're just looking at a cell and describing it and calling it alive, then, right?
So, you agree that viruses aren't alive? Your definition doesn't cover them.

What about viruses that have membranes? And a kind of respiratory cycle?

Such as?

 

[Vkothii]

Never heard of such a virus.

Such as?

These guys:
"
Whilst not strictly a method of classification, Mimivirus joins a group of large viruses known as nucleocytoplasmic large DNA viruses (NCLDV).
They are all large viruses which share both molecular characteristics and large genomes.
The mimivirus genome also possesses 21 genes encoding homologs to proteins which are seen to be highly conserved in the majority of NCLDVs, and further work suggests that mimivirus is an early divergent of the general NCLDV group.

...it codes for several products previously not thought to be encoded by viruses ...mimivirus is not dependent on the host cell genome for coding the metabolic pathways for these products.
They do however, lack genes for ribosomal proteins, making mimivirus dependent for protein translation and energy metabolism.
These factors combined have thrown scientists into debate over whether mimivirus is a distinct form of life, comparable on a domain scale to Eukarya, Archaea and Bacteria.
Nevertheless, mimivirus does not exhibit the following characteristics, all of which are part of many conventional definitions of life: homeostasis, response to stimuli, growth in the normal sense of the term (instead replicating via self-assembly of individual components) or undergoing cellular division."

Q: Does your car work?
A: Only when I drive it.
Q: What does a car have to do with viruses?
A: Nothing, it's a meaningless comparison: viruses aren't driven around by humans.

Q: Are viruses evolved?
A: Yes
Q: Doesn't that conflict with a definition of life?
A: No
Q: Why not?
A: What, now you want a lesson on how viruses evolve?
Q: How do viruses evolve?

 

[Vkothii]

Basically, you're just looking at a cell and describing it and calling it alive, then, right?
So, you agree that viruses aren't alive? Your definition doesn't cover them.

The definition includes things that a virus doesn't have or exhibit.

But they persist, they reproduce, and they possess functional structures.
Thanks to their ability to co-opt processes in a host cell.

Otherwise, they obviously fall outside the set of "normally respiring" lifeforms.
Is there another viewpoint that might get around this definition issue?

Or it isn't important; at least you don't think virologists are concerned about how to define what a virus is, in terms of structure and function.
I think they do, not every working day, maybe, but the conclusion that viruses aren't alive, as we understand "life", is still open to debate, I would say.

 

[Idle Mind]

Viruses are even lacking criteria from your own definition. But our semantic arguments on what is and isn't alive has no bearing on whether or not a virus will continue being a virus. So what's the point of this discussion, exactly? Are you fearing that we are somehow taking something away from viruses by not classifying them as alive?

 

[Vkothii]

Viruses are even lacking criteria from your own definition.

Sorry? What does that mean? What criteria are you talking about?
Of course what we believe we understand of absolutely anything, has little bearing on whether that thing will continue to be what it is.
So what?

 

[Vkothii]

Viruses don't control what they do, either.

How can viruses "do" something if they have no control - if they're passive chemical "packages"?

I think you've got this wrong. Viruses control "what they do" - the puncturing of a cell membrane is presumably a response of some kind? The insertion of genes into the host genome is controlled by enzymes delivered by the virus.

Once viral genes are being transcribed and viral proteins are being produced without any control by the cell's regulatory mechanisms, the viral genome is in control - the cell is producing viral protein in an unregulated manner. Or the viral genome "gets around" the cells normal regulation of expression by presenting an unregulated set of genes for the cell to transcribe.

A bacteria does mysterious stuff, yet isn't considered alive.

You want to have another go at this? I think there could be a few biologists who would disagree completely with the notion that bacteria aren't living organisms.

 

[Stryder]

A simple conclusion is to apply "Computer Viruses" to the terminology. A "Computer Virus" can only deliver it's payload if the 'Host' is compatible with it. Basically it's a piece of code that does a specific task only if that code can be interpreted.

The same thing applies to real Viruses. Viruses don't evolve on their own, they are "Interpreted" by a host and depending on how that host is configured in regards to it's genetic structure defines the outcome of it's 'Evolution'. Technically a virus would not evolve on it's own without a host to duplicate and alter it's coding.

This is why I don't class Viruses as being life or 'alive'.

 

[Vkothii]

Technically a virus would not evolve on it's own without a host to duplicate and alter it's coding.

This is why I don't class Viruses as being life or 'alive'.

Good for you.
What about how they got started?
Would you say they maybe arose because of horizontal gene transfer between prokaryotes? Would that be a plausible way for them to have come into their own as functional, packaged "information" and structure?

 

[invert_nexus]

But they persist, they reproduce, and they possess functional structures.
Thanks to their ability to co-opt processes in a host cell.

It's important to note that viral enzymes are quiescent until the virus contents are released inside the cell. They don't do anything within the virus capsid itself.

Is there another viewpoint that might get around this definition issue?

You can define life however you like. You can define life to contain viruses if you like. It really doesn't much matter, except conceptually.

at least you don't think virologists are concerned about how to define what a virus is, in terms of structure and function.

You continually amaze me at your ability to misunderstand what people are saying. Do you do it on purpose?
Nobody ever said virologists aren't concerned with defining what a virus is. That's stupid. They aren't much concerned with spending their lives debating the definition of life, however. I'm sure they spend some time on the debate but generally realize it's all semantic and not that important to what a virus actually is and does.

Sorry? What does that mean? What criteria are you talking about?

The criteria. That you gave in your definition of life. A virus isn't contained in your definition of life...
Sheesh.

I think you've got this wrong. Viruses control "what they do" - the puncturing of a cell membrane is presumably a response of some kind? The insertion of genes into the host genome is controlled by enzymes delivered by the virus.

Viral entry into a cell is mediated by simple chemical reactions on the enzyme level. Proteins touch and react according to simple (well, not so simple) chemical rules.

I forget whether it's hiv or the flu where a trimer is cleaved into its three strands. Each strand moves apart from the other two. This, in effect, pulls the cell membrane closer to the viral envelope thus triggering a merging of the envelopes. Etc.

It's not like the virus goes, "Hmm. A cell. Muaha! I'm going to penetrate this tasty morsel and have my way with her." *fingers oily mustachio*

Viruses work because of the way their proteins are structured.

Their proteins work because they have to work that way because of their physical structure.

Their is no choice involved.
Their function is mandatory.

Once viral genes are being transcribed and viral proteins are being produced without any control by the cell's regulatory mechanisms, the viral genome is in control - the cell is producing viral protein in an unregulated manner. Or the viral genome "gets around" the cells normal regulation of expression by presenting an unregulated set of genes for the cell to transcribe.

Is the viral genome alive then? You're talking about it as if it were in control. Control seems to be a major part of your definition of life despite the fact that it doesn't seem to be a major constituent of your definition of life.

To answer your question, no, the viral genome is not alive. And by most definitions, neither is the virus. However, generally, the cell is considered to be alive, and is still alive even when infected with the virus which has coopted its control mechanisms. The virus depends upon that life (rather the processes by which the cell is considered alive) to function.

The same thing applies to real Viruses. Viruses don't evolve on their own, they are "Interpreted" by a host and depending on how that host is configured in regards to it's genetic structure defines the outcome of it's 'Evolution'. Technically a virus would not evolve on it's own without a host to duplicate and alter it's coding.

Not entirely. Many viruses contain their own transcriptases which are notoriously prone to error. That's why viruses evolve so fast.
(Or is it the ribosome... I forget details.. Hercules, help me out here?)