Final answer:
2,4-Dinitrophenol (DNP) uncouples oxidative phosphorylation by making the mitochondrial membrane permeable to protons, which bypasses ATP synthase and releases energy as heat instead of forming ATP, leading to increased metabolic rate and weight loss.
Step-by-step explanation:
The mechanism by which 2,4-dinitrophenol (DNP) uncouples oxidative phosphorylation from electron transport is through its ability to transfer protons across the mitochondrial membrane, thus bypassing ATP synthase. Normally, in the process of oxidative phosphorylation, a proton gradient is generated across the inner mitochondrial membrane as electrons are passed along the electron transport chain (ETC). This proton gradient is then used by ATP synthase to generate ATP from ADP and inorganic phosphate.
However, DNP acts as an uncoupler by making the inner mitochondrial membrane "leaky" to protons. This leakiness allows protons to flow back into the mitochondrial matrix without passing through ATP synthase, which means energy from the electron transport chain is released as heat instead of being captured in the form of ATP. As a result, the potential energy stored in the proton gradient is dissipated, and no ATP is formed even though the ETC is functioning. This explains the efficiency of DNP as a weight-loss drug, as the caloric energy of food is released as heat rather than stored, although due to severe side effects, including hyperthermia and possible death, DNP is not used for this purpose anymore.