Forums → WEPR → Edge Of Life

It's just that for example, I don't think viruses have to destroy the nucleus, or enter it at all, really. It depends on the type (DNA, RNA, retro) but the ribosomes for instance are outside the nucleus, so the viral RNA would simply need to swim around and wait for a ribosome to come.
On the other hand, some viruses can enter a lysogenic cycle where they actually insert their genome into the cells genome, the cell divides, and then a whole cohort of cells are infected without having been killed. This of course necessitates a passing through the nucleus membrane.

Another point I want to check is if the capsid is a bilayer or, as I think, just a simple protein coat. Bilayers usually are made of lipids.

But I'll check in my big book when I get home.

Ok, so the book I wanted to read is more based on genetics and so wasn't as big a help I thought it would be. But I still have some points.

Concerning the capsid structure, I see no mention anywhere that it is a bilayer. Bilayers usually are lipid layers, as the single elements must have a hydrophobic and a hydrophilic end. Some amino acids have hydrophilic or hydrophobic parts, which helps forming the correct protein structure for a specific function; but I never heard of a whole layer done in such a fashion.

Also I found this article to be interesting:
https://en.wikipedia.org/wiki/Capsidhttps://en.wikipedia.org/wiki/Capsid

The part in the article under "Chemical properties" may also give us a solution to one of the other problems: the metastability of the capsid structure, achieved when assembled in the cell, is likely a key property for later insertion of the virus genome into a host cell. Release of the genetic material into the host cell may be the state of least energy for the capsid, which would mean that it is an entropic, passive process.

However, for all the rest I have to admit I didn't find much about the exact processes. It was mentioned that the virus will also repress translation of the cells genome in favour of its own; how it does that, I don't know. What I do know is that the virus' genome certainly doesn't need to destroy a nucleus; either because it is a bacteriophage and bacterias don't have a nucleus, or in the case of eucaryotic cells it likely can pass the core membrane easily. RNA strands transcribed from the cell genome can readily pass the nucleus membrane; and as the translation machinery making proteins from RNA is outside the core, the viral RNA doesn't have to bother.

How it works with viral DNA and how they keep safe in the cell, I didn't find out either. In the end you could still be right. I personally think it is all passive somehow, but can't explain how.

So let me get this straight, you pointed out a misconception and an error on my part, but fail to explain it completely?

I still have a few challenges to your argument, anyways

so the viral RNA would simply need to swim around and wait for a ribosome to come

some viruses can enter a lysogenic cycle where they actually insert their genome into the cells genome, the cell divides, and then a whole cohort of cells are infected without having been killed. This of course necessitates a passing through the nucleus membrane.

Concerning the capsid structure, I see no mention anywhere that it is a bilayer. Bilayers usually are lipid layers, as the single elements must have a hydrophobic and a hydrophilic end. Some amino acids have hydrophilic or hydrophobic parts, which helps forming the correct protein structure for a specific function; but I never heard of a whole layer done in such a fashion.

So let me get this straight, you pointed out a misconception and an error on my part, but fail to explain it completely?

So it's not passive, isn't it? unless you meant "drift" around

before inserting their genome to the host cell's DNA, doesn't it need to produce Helicase, a special enzyme to cut DNA's (in case you don't know what this is, it's Indonesian version is Helikase, which i tried to translate to Helicase)? wouldn't that made the virus to be active, at least inside the nuclei?

Well, i asked my teacher today, and she specifically says that it HAD to be an amino acid bi-layer, having a hydrophilic and hydrophobic "legs". because if it was not, it would literally dissolve in water, destroying the virus apart. Now I'm extremely confused. What is the name of the book you read?

so, would a "lifeform" be alive?

anyway, i'm going to be out for a very long time. I'm facing a computer ban. see you all

so, would a "lifeform" be alive?

Let's study this for a bit:

[url]http://infohost.nmt.edu/~klathrop/7characterisitcs_of_life.htm[/url]

It seems what most people are having impasses with are the reproductive purposes. But there is one more thing that a virus lacks, and that is the "chemical machinery" or enzymes to carry out the chemical reactions for life. They require a host cell in order to reproduce, but the viruses still do not "grow".

[url]http://science.howstuffworks.com/life/cellular-microscopic/virus-human1.htm[/url]

It says here that most scientists still agree that a virus is alive, because of the reactions that take place when a virus infects a cell. There is still a fine line between living and non-living, and viruses are sitting right on top of it.

I think after some reading it seems viruses really don't do anything by themselves. The host cell replicates their genome and translates all proteins for which it codes. Those proteins are partly structure proteins that self-assemble with all the necessary genome and proteins to assure a future hijacking of a cell, and partly those very proteins that will force the future host cell to replicate the virus.

On the other hand, I have been realising that this alone is a bad way to separate life from non-life. After all, I am convinced that even life is ultimately based on reactions following strictly the principles of chemistry and physics.

So the best point we have right now is the total and utter lack of any metabolism and homeostasis in viruses.

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Another way to approach this topic might be to define death. If we can define death, and if viruses do not "die" by this definition, can we still consider it alive?

death

That definition seems pretty good, at least for simple life. I would slightly adapt that, however. Many microorganisms can enter a stadium in which their normal processes are slowed down or interrupted to allow them to wait for better times. Hence this:

"When an organism irreversibly ceases to perform the processes that keep it alive."

So what if we apply this to viruses? What are the processes keeping a virus alive? Aren't those exactly those processes performed by the host cell and not the virus itself?

So what if we apply this to viruses? What are the processes keeping a virus alive? Aren't those exactly those processes performed by the host cell and not the virus itself?

I'm back from the brink, a computer ban brink.

By definition, yes.
"A life form or lifeform is an entity or being that is living or alive."

........Basin Groups 1-9 (which collectively make up the Pre-Nectarian), and the Nectarian and Lower Imbrian. The first lifeforms (self replicating RNA molecules, see RNA world hypothesis) may have evolved on earth around 4 bya during this era.

Something that cannot die because it does not perform life sustaining processes cannot possibly be alive.

Ok then, can anyone explain this paragraph i got from wiki?

[quote] ........Basin Groups 1-9 (which collectively make up the Pre-Nectarian), and the Nectarian and Lower Imbrian. The first lifeforms (self replicating RNA molecules, see RNA world hypothesis) may have evolved on earth around 4 bya during this era.

..... especially the bolded sentence, because according to most of your posts, they shouldn't qualify as a "lifeform" or be "alive", yet why do they write this? [/quote]
In my modest opinion, qualifying RNA as the first lifeforms is arguably false.

First, I would not qualify them as lifeforms; they are organic molecules that can both contain information as well as act enzymatically; such molecules were certainly vital for the first lifeforms, but it isn't a lifeform by itself.

Second, the RNA we know today was likely not the very first of that molecule category. There are a wide variety of bases, the ones modern genetic information is made of (U,G,C,A,T) were not necessarily the first.

what about immortalized cell lines? are they not living, because they can't die by natural means? more explanation is in here, but if you are too lazy to read it, what i infer from them is that they include cancerous cells.

Then again, those immortal cells still perform &quotrocesses that keep it alive". If an individual cell would stop those processes, which is still possible (deleterious mutations in vital parts of the genome, lack of resources for growth) this cell would still die. Remember that cancerous cells induce angiogenesis in the surrounding tissue to sustain their increased growth rates.

A virus, as opposed to an immortal cell line, never performed those processes to begin with. In a way it doesn't even have the possibility to die.