Final answer:
In an oxygen-reduction (redox) reaction, electrons are transferred from the oxidizing substance to the reducing substance. Redox includes cases like the disproportionation of hydrogen peroxide and the reduction of oxygen in biological systems.
Step-by-step explanation:
The component transferred between substances in an oxygen-reduction reaction, or redox reaction, is electrons. When a substance undergoes oxidation, it loses electrons and is considered the reducing agent, while the substance that gains electrons through reduction is considered the oxidizing agent. A classic example of a redox reaction is the disproportionation of hydrogen peroxide (H2O2), where oxygen is both oxidized and reduced.
To illustrate a redox reaction, let's consider the reaction between zinc metal and hydrogen ions. In this reaction, zinc loses electrons (oxidation) and hydrogen ions gain electrons (reduction). This process highlights the fundamental redox principle that electrons are always transferred from the oxidized substance to the reduced one.
Additionally, reactive oxygen species in biological systems, like those encountered in the electron transport chain, are involved in redox reactions where oxygen is reduced by electrons and protons to form water. This too demonstrates the transfer of electrons, characteristic of redox reactions.