Starting a new thread as a way to kill boredom............................
So, do you guys believe virus, prions and RNA's living? i have read multiple article on wikipedia that seems to show different sides to this problem, but no sides have really won
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.
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.
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.
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
So it's not passive, isn't it? unless you meant "drift" around
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.
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?
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.
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 let me get this straight, you pointed out a misconception and an error on my part, but fail to explain it completely?
I think I did explain one or two things (the issues I pointed out beforehand), I just couldn't find out as much as I wanted about the rest; I couldn't find enough detailed information to show that it is passive or active.
So it's not passive, isn't it? unless you meant "drift" around
Drift is what I meant. Like the cells own strands.
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?
Honestly I have no idea how they would do it, but as they apparently can supress the cells own genome expression, I guess they can also hijack the cells own replication proteins which will insert the viral genome. But don't ask me how this happens.
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?
It's a book about genetics and with the detailed molecular mechanisms related, but nothing detailed about viruses. It just says it's proteins. But I think this makes sense to me now, that it must be constituted of amino acids with the two 'leg' types.
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".
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?
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?
Actually scratch that, it is even simpler. The processes performed by the host cell are linked to replication, not keeping the virus alive. As a virus has no metabolism or homeostasis, it has no such processes at all. So essentially, it cannot die according to 09philj's definition. Something that cannot die because it does not perform life sustaining processes cannot possibly be alive.
By definition, yes. "A life form or lifeform is an entity or being that is living or alive."
Ok then, can anyone explain this paragraph i got from wiki?
........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?
Something that cannot die because it does not perform life sustaining processes cannot possibly be alive.
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.
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.
Good point. I guess this is a weak spot in the definition of life by death.
Then again, those immortal cells still perform "rocesses 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.
