Electron Transport Chain: Study Notes

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Step 1: Electron Transport Chain

• Consists of a series of proteins and organic molecules located in the inner mitochondrial membrane.
• Its primary function is to capture energy in the form of a proton gradient.

Step 2: Chemiosmosis

• The proton gradient generated is utilized to synthesize ATP.
• Along with the electron transport chain, this process constitutes oxidative phosphorylation.

Step 3: Complex I to IV

• Involves proteins and organic molecules organized into four distinct complexes (I to IV).

Step 4: NADH in Complex I

• NADH donates high-energy electrons directly to Complex I.
• These electrons are used to pump protons (H⁺) across the membrane.

Step 5: FADH₂ in Complex II

• FADH₂ donates electrons to Complex II.
• Unlike Complex I, Complex II does not pump protons.

Step 6: Ubiquinone (Q)

• Acts as a mobile electron carrier.
• Transfers electrons from Complex I and Complex II to Complex III.
• It is reduced to form QH₂.

Step 7: Complex III to Cytochrome C

• Electrons pass through Complex III, resulting in additional H⁺ ions being pumped across the membrane.
• Electrons are then transferred to Cytochrome C (cyt C).

Step 8: Complex IV and Water Formation

• Electrons are carried to Complex IV.
• Protons (H⁺) are pumped across the membrane, and electrons are passed to O₂.
• O₂ splits into oxygen atoms, which combine to form water (H₂O).

Step 9: Reduction of O₂

• Four electrons reduce each molecule of O₂.
• This reduction results in the formation of two H₂O molecules.

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