BIOCHEMISTRY 244
A2 NOTES
, THEME E
Oxidative Phosphorylation
Oxidative phosphorylation couples electron transport (oxidation of NADH & FADH₂) to the
synthesis of ATP from ADP + Pi. ItÕs the Þnal stage of aerobic respiration, occurring in
mitochondria.
1. Overview of Aerobic Respiration
Aerobic respiration consists of four sequential stages:
,2. What Is Oxidative Phosphorylation?
An exergonic oxidation of electron carriers (NADH, FADH₂) by the electron transport chain
(ETC), coupled to the endergonic phosphorylation of ADP → ATP.
Overall reaction:
Key players:
• Electron donors: NADH, FADH₂
• Electron acceptor: O₂ (Þnal acceptor → forms H₂O)
• Coupling mechanism: Electron ßow drives proton pumping → chemiosmotic gradient →
ATP synthesis via ATP synthase.
3. Site and Structure of Oxidative Phosphorylation
Mitochondrial structure:
• Outer membrane: Permeable to small molecules and ions.
• Inner membrane:
Impermeable to H⁺ and most solutes.
Contains ETC complexes (IÐIV) and ATP synthase (V).
• Matrix: Site of pyruvate oxidation, citric acid cycle, and fatty acid oxidation.
Components:
, 4. Redox Reactions & Electron Transfer
Basic principles:
• Oxidation: Loss of e⁻ or H⁺
NADH → NAD⁺ + H⁺ + 2e⁻
• Reduction: Gain of e⁻ or H⁺
O₂ + 4e⁻ + 4H⁺ → 2H₂O
The electron donor (reducing agent) is oxidised.
The electron acceptor (oxidising agent) is reduced.
Direction of e⁻ ßow:
Always from lower to higher reduction potential (E¡′).
A2 NOTES
, THEME E
Oxidative Phosphorylation
Oxidative phosphorylation couples electron transport (oxidation of NADH & FADH₂) to the
synthesis of ATP from ADP + Pi. ItÕs the Þnal stage of aerobic respiration, occurring in
mitochondria.
1. Overview of Aerobic Respiration
Aerobic respiration consists of four sequential stages:
,2. What Is Oxidative Phosphorylation?
An exergonic oxidation of electron carriers (NADH, FADH₂) by the electron transport chain
(ETC), coupled to the endergonic phosphorylation of ADP → ATP.
Overall reaction:
Key players:
• Electron donors: NADH, FADH₂
• Electron acceptor: O₂ (Þnal acceptor → forms H₂O)
• Coupling mechanism: Electron ßow drives proton pumping → chemiosmotic gradient →
ATP synthesis via ATP synthase.
3. Site and Structure of Oxidative Phosphorylation
Mitochondrial structure:
• Outer membrane: Permeable to small molecules and ions.
• Inner membrane:
Impermeable to H⁺ and most solutes.
Contains ETC complexes (IÐIV) and ATP synthase (V).
• Matrix: Site of pyruvate oxidation, citric acid cycle, and fatty acid oxidation.
Components:
, 4. Redox Reactions & Electron Transfer
Basic principles:
• Oxidation: Loss of e⁻ or H⁺
NADH → NAD⁺ + H⁺ + 2e⁻
• Reduction: Gain of e⁻ or H⁺
O₂ + 4e⁻ + 4H⁺ → 2H₂O
The electron donor (reducing agent) is oxidised.
The electron acceptor (oxidising agent) is reduced.
Direction of e⁻ ßow:
Always from lower to higher reduction potential (E¡′).
