Here's how it happens:

1. Electrons are passed down the chain: Electrons, energized from the breakdown of glucose, move from molecule to molecule in the chain, losing energy along the way.

2. Protons are pumped across the membrane: This energy is used to pump protons (H+) from the mitochondrial matrix to the intermembrane space, creating a concentration gradient.

3. Protons flow back through ATP synthase: The protons flow back across the membrane through a protein called ATP synthase, generating ATP (the energy currency of the cell).

4. Water is formed: At the end of the electron transport chain, the electrons and protons combine with oxygen (O₂) to form water.

This process is essential for cellular respiration, as it provides the energy needed for the cell to function.