In which part of the phototransduction pathway is all-trans-retinal transported to the cytoplasm?

The transport of all-trans-retinal to the cytoplasm occurs in the photoreceptor disc lumen. During phototransduction, when light is absorbed by the photopigment rhodopsin, it leads to a conformational change in retinal, converting 11-cis-retinal to all-trans-retinal. This process initiates a cascade of biochemical reactions that ultimately contribute to the visual signal.

After the photoisomerization of retinal, all-trans-retinal is released from rhodopsin and accumulates in the outer segment of the photoreceptors within the disc membranes. It is then transported into the cytoplasm of the photoreceptor cells through various cellular mechanisms. The disc lumen acts as the initial space where the retinal resides before being transported.

Understanding this context helps elucidate the processes involved in phototransduction and the specific role of the disc lumen in the lifecycle of retinal.