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Evolution of Krebs Cycle- why 6C?

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biog:
Just curious as to the reasons/logic behind having 6 carbons in the Krebs cycle and why the cells of aerobic organisms have evolved to use molecules of up to 6 carbons.

thanks!

Donaldson Tan:
something to do with glucose?

Borek:
It just occured to me... There are trioses, tetroses, pentoses, hexoses and heptoses. Of these pentoses and hexoses are most popular and abundant. They have one thing in common - they can create a reasonably stable rings that are used in the polymeric compounds (polyhydrocarbons and nucleic acids - quite usefull in all living organisms). If these polymers are more stable than other similar compounds that can be the reason for pentoses and hexoses abundance.

I wonder how much starch and celluose stability can be atributed to the six atoms ring they are made off. Are there analogous compounds made of heptoses? Cycloheptoses? Tetroses/cyclotetroses?

Hispania:
I suppose the evolution has led to this specification. I think pentoses and hexoses can create polymeric compounds, as the same way as aminoacids can make stable proteins.

The key must be in the way the hexoses turn around Krebs cycle, so no other molecule can do it.

Borek:

--- Quote from: Hispania on September 04, 2006, 03:40:06 PM ---I suppose the evolution has led to this specification. I think pentoses and hexoses can create polymeric compounds, as the same way as aminoacids can make stable proteins.

The key must be in the way the hexoses turn around Krebs cycle, so no other molecule can do it.
--- End quote ---

Krebs cycle was tuned to prepare hydrocarbons needed for other things, not other things were prepared to use output of tuned Krebs cycle.

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