Final answer:
Hydrogen ions moving through ATP synthase is an example of facilitated diffusion, a form of passive transport that relies on the energy from a concentration gradient and involves a specific transmembrane protein.
Step-by-step explanation:
Hydrogen ions moving through ATP synthase is an example of facilitated diffusion. This process involves the movement of hydrogen ions across a mitochondrial membrane through a protein called ATP synthase, which uses the energy to synthesize ATP from ADP and inorganic phosphate.
It's a type of passive transport because it does not require the input of cellular energy (ATP); instead, it uses the potential energy stored in a concentration gradient. Furthermore, facilitated diffusion is characterized by molecules or ions moving down their concentration gradient through specific transmembrane proteins, unlike active transport, which requires energy to move substances against their gradient.
Chemiosmosis is closely related to this process, where a gradient of hydrogen ions created by the electron transport chain provides the energy necessary for ATP synthase to function as the ions pass through it. This flow of hydrogen ions is an example of the transformation of potential energy from an electrochemical gradient into the chemical energy of ATP, utilizing the enzymatic properties of ATP synthase.