Assume that the conversion of oxidized ubiquinone to reduced...

Assume that the conversion of oxidized ubiquinone to reduced ubiquinone by NADH dehydrogenase occurs on the matrix side of the inner mitochondrial membrane and that its oxidation by cytochrome c reductase occurs on the intermembrane-space side of the membrane (see Figures $14-14$ and $14-21$ ). What are the consequences of this arrangement for the generation of the $\mathrm{H}^{+}$ gradient across the membrane?

Key Concepts

Chemiosmotic Theory

This theory explains how the energy from electron transfer is used to drive protons across a membrane against their concentration gradient, creating an electrochemical potential (proton motive force) that is then utilized for ATP synthesis via ATP synthase.

Electron Transport Chain

The electron transport chain is a series of protein complexes within the inner mitochondrial membrane that transfer electrons from carriers like NADH to oxygen. During this process, some complexes pump protons from one side of the membrane to the other, thereby establishing a proton gradient.

Vectorial Proton Transport

Vectorial proton transport refers to the directional movement of protons across the mitochondrial inner membrane. The separation of sites where electrons are received and donated results in protons being pumped from the mitochondrial matrix to the intermembrane space, effectively creating the gradient used for energy production.

Membrane Topology and Compartmentalization

The spatial arrangement of complexes in the inner mitochondrial membrane, particularly their specific orientations (one acting on the matrix side and another on the intermembrane space side), is crucial. This organization ensures that protons are effectively translocated across the membrane, thereby generating and maintaining the proton gradient essential for the process of oxidative phosphorylation.

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