<P> Photosynthetic electron transport chains are discussed in greater detail in the articles Photophosphorylation, Photosynthesis, Photosynthetic reaction center and Light - dependent reaction . </P> <P> Electron transport chains are redox reactions that transfer electrons from an electron donor to an electron acceptor . The transfer of electrons is coupled to the translocation of protons across a membrane, producing a proton gradient . The proton gradient is used to produce useful work . About 30 work units are produced per electron transport . </P>

Where is the electron transport chain located in eukaryotes and prokaryotes