Final answer:
DNP makes the inner mitochondrial membrane permeable to protons, disrupting ATP production and increasing energy release as heat, which may contribute to weight loss. However, due to serious health risks, it is no longer used.
Step-by-step explanation:
Dinitrophenol (DNP) is an uncoupler that makes the inner mitochondrial membrane leaky to protons (H+). DNP was historically used as a weight-loss drug because it disrupts the proton gradient across the mitochondrial membrane, which is essential for ATP synthesis. During normal cellular respiration, hydrogen ions (protons) are pumped across the inner mitochondrial membrane, creating an electrochemical gradient. This gradient is then used by ATP synthase to generate ATP, the cell's energy currency. However, when DNP is present, it allows protons to flow back into the mitochondrial matrix without passing through ATP synthase, effectively bypassing ATP production.
The change in pH across the inner mitochondrial membrane caused by DNP would be a reduction in the gradient, as protons would re-enter the mitochondrial matrix, leading to less ATP production and more energy being released as heat. This increase in thermogenesis could explain why DNP was considered an effective weight-loss drug. However, due to its dangerous side effects, including hyperthermia, tachycardia, and risk of death, DNP is no longer used for this purpose.