The document summarizes electron transport chain (ETC) and ATP synthase. It describes: 1) ETC consists of 5 complexes (I-IV and V) in the mitochondria that transport electrons from nutrients to oxygen, pumping protons out and building up a proton gradient. 2) Complexes I, III, and IV pump protons out while Complex V (ATP synthase) uses the proton gradient to phosphorylate ADP, producing ATP. 3) Electrons are passed through complexes via electron carriers like NADH, FADH2, and cytochromes while protons are pumped from the matrix to the intermembrane space.