The electron transport chain (ETC), or respiratory chain, is linked to proton movement and ATP synthesis. Select the statements that accurately describe the electron transport chain. Electrons generated by the citric acid cycle in the intermembrane space enter the ETC. The reactions of the ETC take place in the inner membrane of mitochondria. Consider what must be true for a proton gradient to be set up across the inner membrane. Electron carriers in the ETC include ubiquinone (coenzyme Q) and cytochrome c. Prosthetic groups, such as iron–sulfur centers, are directly involved with electron transfer. Electron carriers are organized into four complexes of proteins and prosthetic groups. Electron transfer in the ETC is coupled to proton transfer from the matrix to the intermembrane space.