Questions re. respiration/metabolism

[Bio-student]

Hi everyone, just a few questions I've been wondering on...

1) Glycolysis is catalyzed by enzymes. Enzyme synthesis requires energy (presumably from glycolysis). Seems there's a bit of a chicken-and-egg situation here: I'm wondering which would've developed first and why?

2) In anaerobic conditions why did the ethanol pathway evolve in some organisms and the lactic acid pathway in others?

3) ATP provides an immediate source of energy in most metabolic processes, whereas GTP, UTP etc. are more specific in the reactions they activate--why is this?

Thanks in advance for any answers...

 

[JakeA]

I'm certainly no expert, but I'll makes some guesses.

1. I'm not sure you can talk in terms of one concept evolving first or second. "Glycolysis" is a human construct, not one in which nature said "OK, I've finished this process, now let's do the next." They probably evolved jointly with similar and mutable processes preceding both of them.

2. My guess would be environmental conditions and the nutrients/energy requirements required for different organisms.

3. Again I'll guess. ATP is probably more energy rich and harder to control. GTP is probably less energy rich but easier to control its reactions, so it's used in regulation more than energy production.