What process involves a series of carrier molecules on the inner mitochondrial membrane that create a proton gradient?

The process that involves a series of carrier molecules on the inner mitochondrial membrane creating a proton gradient is the electron transport chain. This sequence of reactions occurs during cellular respiration and is crucial for the production of ATP, the energy currency of the cell.

In the electron transport chain, electrons derived from NADH and FADH2—generated from previous stages of respiration like the Krebs cycle—are transferred through a series of proteins embedded in the inner mitochondrial membrane. As these electrons move through the chain, they lose energy, which is used to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space. This action creates an electrochemical gradient, where there is a higher concentration of protons outside the matrix than inside.

This proton gradient is essential because it creates potential energy, akin to water held behind a dam. The protons flow back into the matrix through ATP synthase, an enzyme that uses this flow to synthesize ATP from ADP and inorganic phosphate. This process is a key part of oxidative phosphorylation.

The other processes listed have different roles in cellular metabolism. The Krebs cycle, while also part of cellular respiration, focuses on the oxidation of acetyl-CoA to produce electron carriers like NADH and FADH