14 Electron Flow in Organotrophy, Lithotrophy, and Phototrophy Smartwork

Redox reactions refer to a pair of reactions in which a particular oxidation is coupled to a corresponding reduction. Although neither can occur independently of the other, it can be helpful to write each oxidation or reduction as a half reaction to help us understand and calculate the flow of energy.

• H₂ → 2H⁺ + 2e^–

• FAD + 2H⁺ + 2e^– → FADH₂

• NADH + H⁺ → NAD⁺ + 2H⁺ + 2e^–

• FAD + 2H⁺ + 2e^– → FADH₂

Oxidation: Loss of electrons

• H₂ → 2H⁺ + 2e^–

• NADH + H⁺ → NAD⁺ + 2H⁺ + 2e^–

Reduction: Gain of electrons

• FAD + 2H⁺ + 2e^– → FADH₂

• FAD + 2H⁺ + 2e^– → FADH₂

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