The electron transport chain primarily functions to produce what molecule?

The electron transport chain (ETC) primarily functions to produce ATP, which is the main energy currency of the cell. This process occurs in the inner mitochondrial membrane during cellular respiration. As electrons are passed along the chain from electron donors such as NADH and FADH2, their energy is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

This gradient generates potential energy, akin to water behind a dam. Protons then flow back into the matrix through ATP synthase, an enzyme that harnesses this flow to convert adenosine diphosphate (ADP) and inorganic phosphate (Pi) into ATP. This chemiosmotic mechanism is known as oxidative phosphorylation, and it accounts for the majority of ATP produced during cellular respiration.

While other options are related to energy metabolism—such as NADH and FADH2, which are important electron carriers, and GTP, which is a nucleotide involved in protein synthesis and signaling—the primary goal of the ETC is the synthesis of ATP through the energy derived from the flow of electrons.