What happens to hydrogen ions (H+) during the flow of electrons in the ETC?

The flow of electrons through the electron transport chain (ETC) is a critical process in cellular respiration and photosynthesis, specifically occurring in the inner mitochondrial membrane and thylakoid membrane, respectively. During this process, hydrogen ions (H+) are actively pumped into the thylakoid space (or intermembrane space in mitochondria) as electrons move down the chain.

This pumping creates a proton gradient across the membrane, where there is a higher concentration of hydrogen ions in the thylakoid space compared to the stroma (in photosynthesis) or the mitochondrial intermembrane space compared to the mitochondrial matrix. The buildup of H+ ions in this confined space creates potential energy that can be harnessed when hydrogen ions flow back through ATP synthase, driving the production of ATP. This process is essential for both ATP synthesis and the overall efficiency of energy production in the cell.

Therefore, the correct response regarding the fate of hydrogen ions during electron transport captures the fundamental mechanism of how energy is generated via the ETC.