Proton motive force

Proton motive force (PMF) is a form of energy that is generated by the transfer of protons (or hydrogen ions) across a membrane, such as the inner membranes of mitochondria or chloroplasts, or the plasma membrane of bacteria. It is the main energy source for the majority of cellular and molecular processes.

Overview

The proton motive force is primarily generated by the electron transport chain, which uses the energy from electrons to pump protons out of the mitochondrial matrix and into the intermembrane space. This creates a concentration gradient of protons, and a charge difference across the membrane, both of which contribute to the proton motive force.

Components

The proton motive force consists of two components: a chemical potential, due to the difference in proton concentration across the membrane, and an electrical potential, due to the charge difference across the membrane. The chemical potential is often denoted as ΔpH, and the electrical potential as Δψ. The total proton motive force is given by the sum of these two components.

Role in ATP synthesis

The proton motive force is used by ATP synthase to generate ATP. Protons flow back across the membrane through ATP synthase, driving the synthesis of ATP from ADP and inorganic phosphate. This process is known as oxidative phosphorylation in mitochondria, and photophosphorylation in chloroplasts.

Role in bacterial flagellar rotation

In bacteria, the proton motive force is used to power the rotation of flagella, which enables the bacteria to move. Protons flow back across the membrane through a rotary motor at the base of the flagellum, causing it to spin.

See also

• Electron transport chain
• ATP synthase
• Oxidative phosphorylation
• Photophosphorylation
• Mitochondria
• Chloroplasts
• Bacteria

References

Proton motive force Resources
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