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Do the simplest bacteria have ribosomes and helicase?

Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.

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Postby Daemach » Wed May 23, 2012 5:13 pm

A cell cannot go on as it is without ATP.
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Postby JackBean » Wed May 23, 2012 5:56 pm

Cell cannot, but what was before cell obviously had to.

You're still thinking only about cells. But already first cells were probably composed of RNA, DNA and proteins, thus this thinking is wrong, because there was no cell without any of these.
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Postby Daemach » Wed May 23, 2012 7:32 pm

I'm thinking about how to get to cells from nothing. I've discovered recently that without helicase, ribosomes and ATP, and several other components, cells cannot function. Evolution is supposed to explain the gap between starting with nothing and fully functioning cells. Therefore, what was before the cell had to use some kind of transitional form of each of these components. It is relevant.
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Re: Do the simplest bacteria have ribosomes and helicase?

Postby jonmoulton » Wed May 23, 2012 9:00 pm

Some chemical reactions were likely producing biochemical precursors and replicating the molecules needed to catalyze the precursor-building reactions prior to their capture within a cell membrane. These reactions that build the parts of the system which catalyzes the reactions are termed a hypercycle. Here are Wikipedia page addressing these ideas:
http://en.wikipedia.org/wiki/Hypercycle_%28chemistry%29
http://en.wikipedia.org/wiki/Prebiotic_evolution
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Postby AstraSequi » Thu May 24, 2012 3:17 am

Evolution does not explain "starting with nothing" - that is abiogenesis. The Theory of Evolution only addresses how change occurs after self-replicating systems are already present.

The major step is to set up a system that can be acted on by natural selection. One of the reasons that an RNA world seems likely is that an autocatalytic set containing RNA is probably able to do this. Ribosomes, ATP, etc would not be necessary at this point - all we know is that they were present by the time we reached the last universal common ancestor.
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Postby JackBean » Fri May 25, 2012 5:34 am

I think this might be of interest for you http://www.researchgate.net/topic/Astro ... Metabolism
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Postby dustman » Fri May 25, 2012 2:13 pm

You want a simple answer to a very hard question that hasn't being properly answered in decades? If you want to speculate, just think of a liposome (bilayer of lipids), with some RNA and nucleotides inside. Just for your info, ATP is RNA. Give it time (billions of years), numbers (huge), additional contaminants and plethora of conditions. Chances something useful and stable will be produced are negligable but given other conditions it might happen. When it happens, you have proto-enzymes capable of manipulating RNA and at later stages DNA and amino acids.

When you think of chemical reaction conditions and energies, take temperature into account. At high temperatures things can go even w/o catalyst present, and pre-life Earth was quite harsh by todays standards.
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Postby Daemach » Fri May 25, 2012 2:34 pm

I don't think ATP is RNA, though it is based on adenine. I don't know the chemistry as well as I should but I think it's adenine + ribose + some phosphorus bonds.

I think I understand the basic theory - it's the billions of years and huge numbers part that is giving me heartburn. Nucleotides have to be synthesized. While I could see a couple occurring by chance naturally, they would have to be produced in, as you say, huge numbers over billions of years. To form DNA and evolve, they would have to be strung together in a perfect sequence, and that sequence would have to persist over millions or billions of generations. The problem is that you can't even get to the second generation without ALL of the nanomachines involved in DNA transcription and replication...and they are created from instructions in DNA.

Hypercycles are an interesting theory, as are autocatalytic RNA sets. Have these been demonstrated in a lab? Technically that's unfair, because intelligence is involved, but it would still be interesting to see if it's possible.

Thanks for the help!
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Postby JackBean » Fri May 25, 2012 8:57 pm

1) RNA composes of ATP besides others.

2) yes, autocatalytic RNA (and even DNA) have been proved in lab

3) the DNA does not have to be strung together in perfect sequence and even more it does not persist over millions or even billions of generations...
http://www.biolib.cz/en/main/

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Postby Daemach » Fri May 25, 2012 9:03 pm

1) I'm not sure what this means.

2) Do you have any links?

3) DNA does have to be strung together in a perfect sequence to create a cell that functions correctly. And my textbook says that had to happen for millions of generations for evolution to work. Am I missing something?
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Postby JackBean » Fri May 25, 2012 9:59 pm

3) how would evolution happen if the DNA was the same?
http://www.biolib.cz/en/main/

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Re:

Postby dustman » Sat May 26, 2012 7:08 am

Daemach wrote:1) I'm not sure what this means.

2) Do you have any links?

3) DNA does have to be strung together in a perfect sequence to create a cell that functions correctly. And my textbook says that had to happen for millions of generations for evolution to work. Am I missing something?


1. Not to be rude but check any biochemistry book for DNA/RNA assembly process and see chemical components involved at both ends of reaction.

2. Check PubMed. It might be tough tho', since #1.

3. Ever heard of cancer and genetic sydromes? Both are far from 'perfect'. Every biological system has inherent failure rate. If failure isn't crucial, it might be preserved and give advantage later on (maybe after dozens of generations) when enviro conditions change. Only handful of proteins are very conserved among different species, f.ex. chromatin, and even in such cases their DNAs doesn't match perfectly due to redundancy of genetic code.
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