Larry Moran cites a great quote from Bill Martin.
Life is an exergonic chemical reaction. It’s the energy releasing redox reaction at the core of metabolism that makes life run, and throughout all of life’s history it is one and the same reaction that has been running in uninterrupted continuity from life’s onset. Everything else is secondary, manifestations of what is possible when the energy is harnessed to make genes that pass the torch.
If you need any of that explained, read Larry’s summary.
I teach cell biology, and that could be the theme for the entire class. The course has a strictly enforced prerequisite of general chemistry, and students typically take it concurrently with organic chemistry. I tell them from day one that this is basically a chemistry course that focuses narrowly on the reactions that go on inside cells, and yes, life is all about electrons getting cycled through reactions that provide the energy that drives other reactions — it’s mostly redox chemistry.
Focusing on that is also helpful in understanding the origins of life, because it really is just a transition from geochemistry to self-contained bags carrying out continuous redox reactions. I teach the first half-year of our second year core curriculum, and we really do emphasize metabolism and the energetics of the cell, while the second half is basic molecular biology that focuses on DNA/RNA. That makes a lot of sense, because as we all know, metabolism came first, information came second.
Love the oft-missed point that life originated from geochemistry! But I’m afraid both Larry and Bill have it wrong. Life is endergonic. It is a self-contained chemical system that uses an external energy source to reproduce itself. If it didn’t need an external energy source, or if it encompassed its own energy source, then, yes it would be exergonic. A more interesting point is that life converts energy to negative entropy, an element of which carries forward historically in ever-increasing complexity. Oxygen is the key to life, as the penultimate electronegative element: a powerful electron sink for redox reactions and in partnership with carbon to form the carbonyl function, an electrophilic synthon of incomparable chemical versatility.
So is it safe to say that metabolism is the egg and information, the chicken? ?
As a chemist, the redox reactions are the key to life on Earth. Both in the conversion of water and carbon dioxide into organic molecules like sugars and amino acids by photosynthesis, giving off oxygen in the process, and the metabolism of these molecules back to to carbon dioxide and water by oxygen dependent life that feeds upon the photosynthetic chemical factories and their byproducts.
Are electrons as energy analogous to flowing water; an energy transfer, not a source of energy?
Energy can neither be created nor destroyed, only transferred, sez the First Law.
But this is backwards. Life is matter that does stuff. Doing stuff requires energy, and usable energy comes from redox reactions. But the point of life is the doing stuff (reproducing, growing, surviving, playing the saxophone), not making the energy available/usable. It’s like saying the loint of automobiles is to keep refineries going. Nope. Point A tyo point B; doing stuff.
“throughout all of life’s history it is one and the same reaction.”
Aha! Design! Hence a Designer!
Ah – I should have added [/Idiocy] iso .
@ChasCPeterson #5:
I think it’s fair to speak of the “point” of automobiles; but of life? Not unless you assume a designer.
blbt5 @1:
No biologist I, but if the net effect is to take free energy from the environment, and return heat/entropy, the change in free energy is negative, making it exergonic. No?
That’s not to say there can’t be endergonic subprocesses going on though, I guess.
I’ve always just thought of life as an entropy engine.
Reproduction is pretty obviously the point of life, speaking generally.
No designer necessary.