In photosynthesis, the electron that travels through the electron transport chain in the thylakoid membrane comes from . in cellular respiration, a molecule of supplies the electron that travels through the electron transport chain. 1. a. atp b. carbon dioxide c. water d. nadh 2. a. atp b. carbon dioxide c. water d. nadh

Answer is NADH.

NADH is very good electron donating agent. So it donates electron and changed to NAD+. The electron from NADH travels from higher energy level to lower energy level releasing energy some of which is used to maintian electrochemical gradient by pumping H+ ion into the intermemebrane space. These electron combine with molecular oxygen to form water at the end of the electron transport chain, while the H+ ion fows back to the matrix, combine with ATP Synthase which increase proton flow to synthesize ATP.