Coenzyme required for tissue respiration is

Coenzyme Q (CoQ) is a quinone derivative with a long, hydrophobic isoprenoid tail. It is also called ubiquinone because it is ubiquitous in biologic systems. CoQ is a mobile carrier and can accept hydrogen atoms both from FMNH2, produced on NADH dehydrogenase (Complex I) and from FADH2, produced on succinate dehydrogenase (Complex II).Ref: Harpers Biochemistry; 30th edition