Similar to PQQ, CoQ10 functions as an antioxidant. It protects cells from oxidative damage and plays a role in the electron transport chain, which is the pathway through which ATP is produced in the mitochondria. However, unlike PQQ, CoQ10 levels in the body tend to decline with age and are further reduced by certain health conditions and medications. Supplementing with CoQ10 has been associated with improved energy levels, reduced fatigue, and enhanced exercise performance.