Two questions remain, and they are tightly linked. First, this entire argument is based on the issue of surface-area-to-volume ratio in prokaryotes. But some bacteria, such as cyanobacteria, are perfectly capable of internalising their bioenergetic membranes, twisting their inner membrane into baroque convolutions, expanding their surface area considerably. Why can’t bacteria escape the constraints of chemiosmotic coupling by internalising their respiration in this way? And second, why, if gene loss is so important, did the mitochondria never lose their full genome, taking the process to
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