Oxidative Phosphorylation

oxidative phosphorylation

The final stage of cellular respiration where NADH and FADH₂ are oxidized to produce ATP using the electron transport chain.

Where does oxidative phosphorylation occur?

In the inner mitochondrial membrane.

What is the chemiosmotic theory?

ATP is synthesized using energy from a proton gradient across the inner mitochondrial membrane, rather than by direct chemical transfer.

What are the two steps of the chemiosmotic process?

1. ETC pumps protons across the membrane (proton-motive force)

2. ATP synthase uses this gradient to generate ATP.

What does Complex I do in the ETC?

Transfers electrons from NADH to ubiquinone (Q), pumps 4 H⁺ across the membrane.

What does Complex II do in the ETC?

Transfers electrons from FADH₂ (via succinate) to Q; does NOT pump protons.

What does Complex III do in the ETC?

Uses the Q cycle to transfer electrons to cytochrome c and pump protons.

What does Complex IV do in the ETC?

Transfers electrons from cytochrome c to O₂, reducing it to H₂O and pumps protons.

What are the final products of the ETC from 2 NADH?

2 NAD⁺, 2 H₂O, and 20 H⁺ pumped (when coupled to O₂).

How many ATP are produced per NADH and FADH₂?

~2.5 ATP per NADH and ~1.5 ATP per FADH₂.

What are the two shuttles used to transfer cytosolic NADH into mitochondria?

Glycerol 3-phosphate shuttle (FADH₂) and malate-aspartate shuttle (NADH).

What is the structure of ATP synthase?

• F₀: membrane-bound, allows H⁺ flow

• F₁: matrix-bound, catalyzes ATP synthesis

What is the binding-change model of ATP synthase?

ATP is formed through conformational changes in F₁ induced by proton flow.

What uncouples ATP synthesis from the ETC?

Uncoupling proteins (e.g. UCP-1) dissipate the proton gradient as heat, used in thermogenesis.

How is oxidative phosphorylation regulated?

By ADP availability and energy demand (low ATP = increased ETC activity).

What is the total ATP yield from complete oxidation of one glucose?

30–32 ATP (depending on the shuttle used).