So, I'm designing a species of sapient extraterrestrials for a series of short stories, and I've gotten to the point of needing to find a significant biochemical difference between life on their world and life on Earth.
One idea I had was to replace glucose with ethanol as the primary molecule for energy storage. This would mean that plants would directly produce ethanol from sunlight, CO2, and water and directly metabolise it; Similarly, ethanol would be the molecule that animal life would prefer to use over anything else and would attempt to break down more complex molecules into. Just to clarify, when I speak of using ethanol for energy, I am not talking about fermenting it into acetic acid, I am talking about aerobically "burning" ethanol for energy. It's fine if glucose has to be used as an intermediate molecule in constructing other things such as cellulose, but everything should be broken down to ethanol when being used for energy.
With that out of the way, what biochemical mechanisms and metabolic pathways would be needed to accomplish this, what is their relative efficiency, and is there anything interesting or unusual about them that I should know about?
There are some things you should bear in mind about local conditions and life:
- The local atmosphere has around 22,000ppm CO2, so any mechanisms that do not work in acidic environments are irrelevant.
- Life on the planet we are discussing uses amino acids not found in any Earth life, so anything that requires that is fine.
So, just to recap: I want to replace glucose with ethanol as the primary energy storage molecule. Ethanol should be directly, aerobically metabolised, although glucose can be used as an intermediary in constructing structural and genetic polymers. It's fine to use amino acids not found in Earth life so long as it can resist acidic conditions. How do I do this, what is the relative efficiency, and is there anything else about the means of doing this I should know?