MCAT Chemical and Physical Foundations of Biological Systems Practice Exam

In the context of redox reactions, oxidation and reduction are fundamental processes that involve the transfer of electrons. Oxidation refers to the loss of electrons by a molecule, atom, or ion. When a compound is oxidized, it effectively has a greater positive charge because it has lost negatively charged electrons. Consequently, this process can also be accompanied by an increase in oxidation state.

On the other hand, reduction involves the gain of electrons. When a compound is reduced, it becomes more negatively charged or has a lower oxidation state, since it is adding negatively charged electrons to its structure.

Thus, the correct statement aligns with the definitions of these terms: a compound that is oxidized loses electrons, and a compound that is reduced gains electrons. This understanding of electron transfer is essential in studying chemical reactions and balancing redox equations in chemistry.