Could early life have relied on respiration without mitochondria?
Yeah, I've been thinking about this a lot lately after reading some stuff on ancient microbes. Back when I was messing around with my old aquarium setup, I noticed how the water got all murky and low-oxygen during a filter crash, yet certain bacteria still thrived in that gunky anaerobic mess. Made me wonder—could the very first life forms have pulled off any kind of respiration at all before these fancy mitochondria showed up through endosymbiosis? Like, was there some primitive way to use electron chains or something without the whole organelle package? Feels wild that early cells might've relied just on basic membrane stuff or glycolysis tweaks. Anyone got thoughts on if aerobic-style respiration could've happened pre-mitochondria, or was it all fermentation back then?

Man, your aquarium story hits home. I've dealt with similar die-offs in my pond out back when the pump failed one summer. On the respiration side, prokaryotes back in deep time definitely managed energy production without mitochondria since those organelles came later from engulfed bacteria. They used their plasma membranes for electron transport in some cases, even for aerobic respiration if oxygen was around in small amounts. But mostly early life leaned anaerobic, like various fermentation paths or other acceptor-based systems. Glycolysis was probably the starter, super ancient and oxygen-free. If you're digging into the stages visually, this cellular respiration chart helped me wrap my head around the differences between what's mitochondrial-dependent and the simpler prokaryotic versions. Just my two cents from piecing together random late-night reads it's crazy how efficient mitochondria made everything, but yeah, life scraped by long before that merger.