Coenzyme Q10 is often mentioned together with mitochondria, the respiratory chain and energy. Behind these terms is a clearly described biochemical function: coenzyme Q10 participates in electron transfer within the mitochondrial membrane.
This article explains what coenzyme Q10 is, how ubiquinone and ubiquinol differ, and why the function of an endogenous substance does not automatically demonstrate an effect from additional intake.
What is coenzyme Q10?
Coenzyme Q10, abbreviated CoQ10, is a fat-soluble, vitamin-like compound. The name “Q10” refers to a quinone ring with a side chain consisting of ten isoprene units.
The human body can produce coenzyme Q10. It is therefore not classified as a conventional vitamin. Smaller amounts also occur in various foods.
Coenzyme Q10 is found primarily in biological membranes. Its presence in the inner mitochondrial membrane is particularly important.
What are ubiquinone and ubiquinol?
- Ubiquinone is the oxidised form of coenzyme Q10.
- Ubiquinol is the reduced form of coenzyme Q10.
Both forms belong to the same redox system. The molecule can accept electrons and subsequently release them. Ubiquinone and ubiquinol are therefore different states of the same coenzyme Q10 system.
What are mitochondria?
Mitochondria are cellular structures in which numerous metabolic reactions take place. Their inner membrane contains several protein complexes collectively known as the respiratory chain or electron transport chain.
Within this chain, electrons are transferred step by step between molecules and protein complexes. Coenzyme Q10 functions as a mobile electron carrier.
What does coenzyme Q10 do in the respiratory chain?
Coenzyme Q10 moves within the inner mitochondrial membrane. It accepts electrons from sources including Complex I and Complex II and transfers them to Complex III.
Electron transport is linked to the movement of protons across the membrane. This creates an electrochemical proton gradient, which ATP synthase uses to form adenosine triphosphate, or ATP.
Electron transfer → proton gradient → ATP formation
Cells use ATP as a transferable carrier of chemical energy in many cellular processes.
Does this function mean that additional CoQ10 produces more energy?
No. The respiratory chain consists of many proteins, enzymes, membrane structures and regulatory mechanisms.
The fact that coenzyme Q10 is a necessary component of this system does not prove that additional intake increases ATP production or physical performance in every person.
The description of a normal biochemical function and evidence of an effect from additional intake are two separate scientific questions.
What does “antioxidant” mean for coenzyme Q10?
Ubiquinone and ubiquinol form a redox pair. In laboratory and model systems, the reduced form can participate in reactions with different molecules in biological membranes.
A chemical reaction under laboratory conditions, a change in a biomarker and a clinically relevant effect are separate levels of evidence. A laboratory result is not automatically equivalent to a demonstrated health effect.
How is coenzyme Q10 absorbed?
Coenzyme Q10 is fat-soluble and only slightly soluble in water. Raw-material form, crystal structure, particle size and formulation can influence measured absorption.
Bioavailability describes the extent and speed at which a substance becomes measurable in the body. A higher blood concentration does not automatically demonstrate a greater clinical benefit.
How should label information be understood?
Descriptions may include the total amount of coenzyme Q10, the form as ubiquinone or ubiquinol, the amount of a mixture, the amount per unit or serving, and other formulation components.
The name of the form alone does not establish how much is absorbed or whether a particular effect occurs.
Is there an authorised EU health claim?
The European Food Safety Authority has assessed proposed health claims relating to coenzyme Q10. These included statements concerning energy-yielding metabolism, protection from oxidative damage, cognitive function and endurance.
The submitted evidence did not establish a sufficient cause-and-effect relationship for these proposed claims. The current general EU list of authorised health claims contains no specific claim for coenzyme Q10.
The correct biochemical statement that coenzyme Q10 is part of the mitochondrial electron transport chain should therefore not be equated with a general promise of increased energy or performance.
Conclusion
Coenzyme Q10 is a fat-soluble endogenous compound and a mobile electron carrier in the mitochondrial respiratory chain. Ubiquinone and ubiquinol are the oxidised and reduced forms of the same redox system.
Its involvement in ATP formation is an established biochemical function. However, this does not automatically mean that additional intake increases energy production or performance.
Biochemical function, bioavailability, biomarkers and clinically demonstrated effects should therefore be considered separately.
Frequently asked questions
Is coenzyme Q10 a vitamin?
No. Because the human body can produce coenzyme Q10, it is not classified as a conventional vitamin.
Are ubiquinone and ubiquinol the same?
They are two redox states of the same coenzyme Q10 system. Ubiquinone is the oxidised form and ubiquinol is the reduced form.
What is the main biochemical role of coenzyme Q10?
Its central biochemical role is to transfer electrons within the mitochondrial respiratory chain.
Does higher bioavailability automatically mean a stronger effect?
No. Bioavailability and clinically demonstrated effects are separate scientific questions.
Scientific sources
- Lenaz G, Genova ML. The role of Coenzyme Q in mitochondrial electron transport. Mitochondrion. 2007.
- Acosta MJ et al. Coenzyme Q biosynthesis in health and disease. 2016.
- Pravst I et al. Comparative bioavailability of different coenzyme Q10 formulations. 2020.
- EFSA NDA Panel. Scientific Opinion on health claims related to coenzyme Q10. 2010.
Note: This article provides general scientific information, does not refer to a specific product and is not a substitute for medical advice, diagnosis or treatment.
