Which one of the following statements about the redox reactions of the electron transport chain is correct?
1 NADH gains electrons in the initial reaction of the electron transport chain.
2 The electron transport chain takes electrons from water and gives them to oxygen.
3 The oxidation of NADH is directly coupled to the reduction of oxygen to water.
4 The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.
5 The redox reactions of the electron transport chain are directly coupled with the synthesis of ATP.