Both protein I and the UCP allow H+ ions to move from a region of high concentration to a region of low concentration. The gradient in protein I drives the formation of ATP through ATP synthase, while the gradient in the UCP drives the formation of thermal energy for the organism’s immediate use and reduces the amount of ATP that can be formed. Hence the correct option is b.
In the inner mitochondrial membrane, both protein I (likely referring to the electron transport chain complexes) and the uncoupling protein (UCP) facilitate the movement of H+ ions from a region of high concentration to a region of low concentration. In the case of protein I, this proton movement contributes to the establishment of a proton gradient that drives ATP synthesis through ATP synthase, a process known as chemiosmosis. On the other hand, the proton gradient in the UCP is utilized differently.
The UCP allows protons to move back into the mitochondrial matrix, generating thermal energy instead of contributing to ATP synthesis. This dissipation of the proton gradient by UCP reduces the efficiency of ATP production but generates immediate thermal energy, a process important for certain physiological functions like thermogenesis. Therefore, option B accurately differentiates the functions of the proton gradients in protein I and the UCP and their respective effects on ATP synthesis. Hence the correct option is b.
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