@Valentijn You will know half of this, but including info for all who read. The role of ubiquionol in the electron transport chain (ETC) is very simple it's one of the links in the chain. In order to make a new ATP synthase (the physical enzyme that implements the ETC) you need a ubiquinol molecule - each mitochondria needs very many of that enzyme hence very many Ubiquinol molecules. In simple terms the ETC is nothing more than a series of molecules that accept, then pass on electrons it's like a uni-directional 'copper wire'. At the end of that 'wire' ATP is made. Most cells also need many mitochondria. Hence requirement = many (per mito) x many (#mitos) Each mito should have a functional life of six weeks then divide into younger fresher mitos: Hence requirement = many (per mito) x many (#mitos) x few (semi-frequent division) Next we have to account for the 'oxidative stress' in PWME - ubiquinol 'disarms' free radicals but becomes the useless (for the ETC) ubiquinone meaning Hence requirement = many (per mito) x many (#mitos) x few (semi-frequent division) x very many (oxidative loss) Add in poor production of CoQ10 and you end up with Mito status Status = Production (low) / Requirement (very high) This seems likely to result in very few, or very geriatric mitos since you can't make functional mitos without the 'right CoQ10' = ubiquiniol.