reaktsioonide järjestus, mille jooksul elektron liigub astmeliselt suurema energitasemega kandjalt madalama energiatasemega kandjale, A cascade of reactions in which an electron moves from a higher energy level carrier to a lower one. Takes place in mitochondrial inner membrane and in the thylacoid membranes of the chloroplasts. Creates a gradient of proton electrochemical potential that is used in the ATP synthesis.