Viruses don't have ANY MOLECULER MOVEMNENT until in host cell????

[mint]

Alright so this isn't exactly a homework question, but a strange thing I encountered in my course book :

 

using visible movement as the defining characteristic of life is not enough.

Movements over very small scales will be invisible to the naked eye –

movements of molecules, for example. Is this invisible molecular

movement necessary for life? If we ask this question to professional

biologists, they will say yes. In fact, viruses do not show any molecular

movement in them (until they infect some cell), and that is partly why

there is a controversy about whether they are truly alive or not.

Why are molecular movements needed for life? We have seen in earlier

classes that living organisms are well-organised structures; they can

have tissues, tissues have cells, cells have smaller components in them,

and so on. Because of the effects of the environment, this organised,

ordered nature of living structures is very likely to keep breaking down

over time. If order breaks down, the organism will no longer be alive. So

living creatures must keep repairing and maintaining their structures.

Since all these structures are made up of molecules, they must move

molecules around all the time.

 

What is this molecular movement all about? Indeed even the molecules inside the viruses must move by brownian motion etc. Or does it refer to movement which is not by a established force? What kind of molecular movement does it refer here which happens in virus inside the host cell but not outside?

 

I couldn't find anything through wiki articles...

Thanks for reading and helping.

[Mr Skeptic]

Brownian motion is random, what they are talking about seems to be transport. Passive transport through a membrane can be accomplished without any energy use, and is essentially "holes" with a special shape to help a specific molecule get through. It just helps diffusion happen faster (or at all). On the other hand, active transport is more like a "pump" and requires energy. This can move molecules in the opposite direction they would naturally diffuse. Since it requires energy, only a metabolically active cell could do this.

[CharonY]

The text is very vague. I doubt that transport mechanisms are meant, as on the biological side it is more a conformational change more than anything else. Viruses do have exporters, to introduce genetic material into host cells, for instance.

More classically it may refer to motor proteins of any kind (actin-mysosin for example). But again, the text except is rather too imprecise for my taste. Maybe passages before that hint at what they may be actually talking about.

[mint]

The previous paragraph talks about the various types of movements that we suppose are a sign of life like growth of plants, running of animals, breathing etc. It does seem that this movement might mean some movement by conversion of internal energy, like the 'pump' or the viral exporter maybe. Anyways, the text is at fault by using the word molecular movement. It shortens the length, but is a bit confusing...