The electron transport chain happens in the inner -mitochondrial membrane. Electrons from ___________ and _____________ are passed down the chain. Then, protons (also called H+ ions) are pumped into the inter-membrain space. This makes an electrical and chemical _______________. Now there are a bunch of H+ ions in the intermembrane space. These H+ ions will flow back into the matrix through an enzyme called ______ _____________. That enzyme attaches a phosphate group to ADP to make ___________.