Final answer:
Complexes I, III, and IV of the ETC are responsible for electron transport and proton translocation across the mitochondrial membrane, which is necessary for creating the proton gradient used in ATP synthesis.
Step-by-step explanation:
Function of Complex I, III, and IV of the ETC
The function of complex I, complex III, and complex IV in the electron transport chain (ETC) is crucial for cellular respiration. Complex I, or NADH dehydrogenase, initiates the transport of electrons by transferring them from NADH to coenzyme Q, simultaneously pumping protons across the membrane to create a proton gradient.
Complex III, or cytochrome oxidoreductase, continues this process by transferring electrons from coenzyme Q to cytochrome c, while further contributing to the proton gradient. Lastly, complex IV, also known as cytochrome c oxidase, finalizes electron transport by reducing oxygen into water and pumping additional protons into the intermembrane space, which helps to establish the proton-motive force utilised in ATP synthesis. Each of these complexes plays a pivotal role in the generation of ATP through oxidative phosphorylation, which is a critical process for energy production in cells.