Fun fact: respiration is what really caused eukaryogenesis and the ability for multicellular life to occur. If archaea (what our nuclear genomes are derived from) weren't being kinda weird in the deep ocean, we would never have existed. Bacteria and archaea (other than eukaryote ancestor) have never created multicellular life. And it's because respiration. (cross posting below from my comment on another thread)<p>For efficient respiration, you need to have the translation/transcription of certain ATP synthase genes near to the membrane for basically JIT-ing them when ready to maintain membrane potential, and hence energy generation. Otherwise, the membrane potential falls apart. This simple need is why there are zero multicellular bacteria and multicellularity evolved 6 times in eukaryotes.
By decoupling the rest of the genome from the JIT bits (ie, mitochondrial DNA), you can scale energy independently of genetic information. So if you need 1000x the energy, you need like 5% more DNA (mitochondrial DNA) instead of 1000x more DNA in your genome.<p>Some estimates say that our eukaryotic genes are in charge of 5000x more energy than the equivalent bacterial gene. Hence, our genomes can inflate that much and its fine. And they have. All that inflation lets us have bullshit hang around in our genome, and hey, sometimes evolution figures out something to do with all that bullshit. We evolved 1000x more complexity than bacteria because we decoupled the performance code from the rest of the code.