If complexes i-iv of the mitochondrial ETC pumped electrons in the opposite direction there will be no formation of electrochemical gradient and hence no synthesis of ATP.
ETC is a series of electron carriers that transport electrons in a sequence along with the pumping of protons to generate an electrochemical gradient across the membrane. This gradient when passes through the ATP synthase generates ATP. The process occurs in the inner mitochondrial membrane.
ATP stands for Adenosine Triphosphate. It is the major source of energy for the body because the breakdown of ATP releases energy through which all the body processes are carried out.
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