How do enzymes help control redox reactions during respiration?

Enzymes, specifically a class known as oxidoreductases, are essential for controlling redox reactions during respiration. While high-energy food sources like glucose are stable and unreactive when exposed to oxygen outside of a living system, enzymes provide the necessary mechanisms to catalyze their rapid oxidation within the cell.1

These enzymes, often functioning as dehydrogenases, facilitate the removal of hydrogen atoms and electrons from substrates. This process typically involves coenzymes (such as NAD+ or FAD) that act as carriers, accepting reducing equivalents from substrates and transferring them through a sequential respiratory chain. By organizing these redox reactions into a series of stepwise transfers, enzymes allow the cell to:2

• Regulate reaction rates: They enable reactions to occur efficiently at physiological temperatures that would otherwise be too slow to sustain life.1
• Conserve energy: By controlling the stepwise transfer of electrons to oxygen, the cell can capture liberated chemical energy to synthesize ATP rather than losing it all as heat.3