The oxidation-reduction substances which take part in the respiratory chain are the following EXCEPT:

Explanation

Cytochrome f is the correct option because it is not a component of the mitochondrial respiratory chain. Instead, it is found in the photosynthetic electron transport system of chloroplasts, where it forms part of the cytochrome b6f complex involved in the light-dependent reactions of photosynthesis. Its role there is to mediate the transfer of electrons between plastoquinone and plastocyanin, which is entirely different from the function of cytochromes in cellular respiration. Therefore, cytochrome f does not participate in the oxidative phosphorylation process of mitochondria and is excluded from the list of redox components in the respiratory chain.Coenzyme Q is an incorrect option because it acts as a mobile electron carrier within the mitochondrial inner membrane, transferring electrons between Complex I (or II) and Complex III.Molecular oxygen is an incorrect option because it serves as the final electron acceptor in the respiratory chain, combining with electrons and protons to form water.Cytochromes b, c, a, and a3 are incorrect options because they are essential components of the electron transport chain, facilitating the stepwise transfer of electrons that drives ATP synthesis.