In a redox reaction, if a molecule gains an electron, what has occurred and how is its energy level affected?

In a redox reaction, if a molecule gains an electron, what has occurred and how is its energy level affected?

• A. It is oxidized and energy decreases
• B. It is oxidized and energy increases
• C. It is reduced and now has a higher energy level
• D. It is reduced and energy decreases

Answer: (C)

Gaining an electron is reduction. When a molecule accepts electrons, it becomes more reduced, and in biological systems the reduced form carries electrons at higher potential energy than the oxidized form. This higher energy content is what allows carriers like NADH to power later steps in metabolism, releasing energy as those electrons move to the electron transport chain. So the best statement is that the molecule is reduced and now has a higher energy level. The alternative ideas about oxidation or energy decreasing don’t fit a gain-of-electrons situation.

Gaining an electron is reduction. When a molecule accepts electrons, it becomes more reduced, and in biological systems the reduced form carries electrons at higher potential energy than the oxidized form. This higher energy content is what allows carriers like NADH to power later steps in metabolism, releasing energy as those electrons move to the electron transport chain. So the best statement is that the molecule is reduced and now has a higher energy level. The alternative ideas about oxidation or energy decreasing don’t fit a gain-of-electrons situation.