Final answer:
The two main functions of the Electron Transport System are production of ATP through oxidative phosphorylation and the establishment of a proton gradient for chemiosmosis.
Step-by-step explanation:
The two main functions of the Electron Transport System (ETS) involve the production of ATP and the establishment of a proton gradient across the mitochondrial membrane. Firstly, the ETS is crucial in the process of oxidative phosphorylation, where it aids in the transfer of electrons between electron carriers and eventually to oxygen, which is the final electron acceptor. This transfer of electrons provides the energy needed to pump protons (H+) across the mitochondrial inner membrane, creating an electrochemical gradient. Secondly, the created proton gradient is harnessed by ATP synthase to produce ATP in a process known as chemiosmosis. As protons flow back into the mitochondrial matrix through ATP synthase, the resulting energy is used to synthesize ATP from ADP and inorganic phosphate (Pi). The ETS is therefore integral to cellular respiration and energy production in cells.