What is the main function of ubiquinone in biological systems?

• A. Acts as a substrate in glycolysis
• B. Serves as an electron acceptor in metabolic pathways
• C. Functions as a coenzyme in protein synthesis
• D. Inhibits oxidative phosphorylation

Answer: (B)

Ubiquinone, also known as coenzyme Q10, plays a crucial role in the electron transport chain, a key component of cellular respiration. Its primary function is to act as an electron carrier, facilitating the transfer of electrons from various metabolic pathways, such as the citric acid cycle and fatty acid oxidation, to the complexes of the electron transport chain.

In this context, ubiquinone accepts electrons and then delivers them to complex III of the electron transport chain, where further transfer leads to the pumping of protons across the inner mitochondrial membrane, ultimately contributing to the generation of ATP through oxidative phosphorylation. This process is vital for energy production in aerobic organisms.

While other options address functions that could be associated with various molecules within cellular metabolism, they do not accurately represent the specific role of ubiquinone. It does not act as a substrate in glycolysis, function as a coenzyme in protein synthesis, or serve to inhibit oxidative phosphorylation.