What is a feedback mechanism?

How do high-energy electrons from glycolysis and the krebs cycle contribute to the formation of atp from adp in the electron transport chain? a. high-energy electrons interact with pyruvic acid to create a phosphate bond with adp, forming atp. b. high-energy electrons supply the needed energy to synthesize atp from the lower-energy adp in the electron transport chain. c. high-energy electrons supply a negative charge which causes the citric acid to oxidize, forming a phosphate group to bond with adp. d. high-energy electrons increase the temperature of adp so it easily reacts to form atp.