Final answer:
Bacteriorhodopsin uses sunlight to pump protons out of the cell, creating an electrochemical gradient used for ATP formation, similar to vision processes in the human eye.
Step-by-step explanation:
Bacteriorhodopsin is a light-activated transmembrane protein found in the plasma membrane of halophilic archaea, specifically in the microorganism Halobacterium salinarum. It functions as a light-driven proton pump.
The protein undergoes a conformational change when exposed to light, specifically in the presence of photons of specific wavelengths. This leads to a series of structural changes in bacteriorhodopsin, resulting in the translocation of protons (H⁺ ions) across the cell membrane, from the inside to the outside of the cell.
The mechanism involves the absorption of light by the retinal chromophore within the protein structure. This causes a change in the retinal conformation, resulting in a series of intermediate states within bacteriorhodopsin. During this process, a proton is released from the protonated Schiff base (PSB) to the extracellular space. Simultaneously, a proton from the cytoplasm binds to a site near the PSB, completing the transport cycle and leading to the net movement of protons out of the cell.
Therefore, bacteriorhodopsin utilizes sunlight energy to pump protons out of the cell, generating a proton gradient across the membrane. This proton gradient can then be used by the cell to produce ATP or for other cellular processes, making bacteriorhodopsin an important protein for energy transduction in Halobacterium salinarum.