Control in a living cell

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Control in a living cell

Postby lateralsuz on March 30th, 2019, 12:14 pm 

I was first drawn to this site by some topics, which I can no longer find, that seemed to ask about the nature of control in a living cell. It was a issue that niggled at my mind during my studies, and which has never been explained.

Cells do not have brains within them. Nor do they seem to have extensive neural networks that could act as a pseudo-brain.

Cells can also exist in isolation, so they do not need to be controlled by outside influences. Yet they are regularly seen to adapt to changing circumstances in appropriate ways.

As was pointed out in the other posts, there are many cellular functions such as adapting internal structures during the reproductive cycle, (while expanding or contracting); or DNA repair; which seem to go far beyond the inevitability of a chemical reaction.

Is anyone aware of factors that could explain what is observed?
(Sorry if this is covered by the other topics - but I can't find them)
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Re: Control in a living cell

Postby SciameriKen on April 11th, 2019, 3:16 pm 

Hi Lateralsuz - I was not sure what you mean by your question? Could you clarify?
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Re: Control in a living cell

Postby lateralsuz on May 13th, 2019, 10:06 pm 

Hi SciameriKen

I have been ill which is why I haven't been on the forum for a while.

DNA is a mechanism which seems to initiate the production of various polymers, (principally proteins, RNA etc).

This is believed to happen because the chemical components of DNA act as a code, as well as a template. In combination with various enzymes and other chemicals, different sections of the DNA code can be switched on or off at different times, in what is believed to be a relatively fixed sequence, in order to produce a living being. The development of that sequence is believed to be the result of trial and error by natural mechanisms over millions of years until a working version emerged.

As some books have pointed out, there is a difference between these 'structural' mechanisms / processes and those which 'react to the moment' - which cannot be pre-coded in the same way because they represent dynamic circumstances that require actions to resolve issues, not just construct things to a fixed template. There's a long list of these activities within individual cells.

By focussing on individual cells rather than an entire body we see the real difficulties with these matters when we try to explain such levels of control without a brain - just relying on chemical processes.

As was pointed out in the other posts, some of these processes are very involved because they do seem to 'investigate' problems before determining an appropriate solution out of many possible responses. Yet conceptually the most sophisticated chemical control mechanism we have thought of is the 'feedback loop' where concentrations of a chemical that get out of balance, can trigger a chemical-based response which regulates those concentration. That hardly seems to deal with these circumstances.

In terms of some cell processes, it has been suggested that codes are used to direct activity, and such chemical codes do seem to be observed, (say on vesicles), but a code that is used in this way suggests a level of purpose that goes beyond whether a chemical reaction occurs or not. Something has to deploy them and then respond them in different ways.

As the other posts tried to point out, we can imagine how a computer chip might regulate complex activity like this, but there is no known computer equivalent in a cell - so what is the latest thinking on how these effects are achieved?

Has there been any more progress in this research?
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Re: Control in a living cell

Postby edy420 on May 14th, 2019, 2:58 am 

Maybe not a computer chips equivelent, but most definitely machines.

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Re: Control in a living cell

Postby lateralsuz on May 18th, 2019, 11:35 pm 

I think you're right about the notion of machines in cells edy420.

Whether we consider motor proteins or ribosomes, there is a level of sophistication that goes beyond what we might expect from a chemical reaction - even with trial and error.

You went for the motor proteins (above) and how they transport cargo (vesicles) to very different but specific destinations around a cell - apparently reading and using a code. However in putting the destination code on a vesicle something must determine an end location and the code relevant to that destination. The motor proteins must also read the code and work out how to navigate the many criss-crossing pathways around the cell. How?

This goes way beyond the simple bumping of two chemicals that then react in an inevitable way.

What gives the control if there is only chemistry?

There are many other examples - and as cells can operate in isolation in a test tube, it can't be direction from a larger brain.
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Re: Control in a living cell

Postby TheVat on May 19th, 2019, 11:04 am 

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