Where are photopigments produced in photoreceptors?

Photopigments are produced in the inner segments of photoreceptors, specifically in both rods and cones. The inner segments contain the cell's machinery, including ribosomes and rough endoplasmic reticulum, which are essential for synthesizing proteins, including the proteins that make up photopigments.

Once synthesized, these photopigments are then transported to the outer segments of the photoreceptors, where they localize within specialized membranes. This separation of photopigment production in the inner segment and its localization in the outer segment is critical for the phototransduction process, allowing photoreceptors to respond to light stimuli effectively.

The outer segments are primarily involved in capturing photons due to their high density of stacked membrane discs containing the photopigments, but they do not contain the cellular machinery necessary for producing these molecules. As such, the inner segment is the correct answer, as this is where the synthesis of photopigments occurs before they are transported to the outer segments for function.