Izvolte
"
The basic light-processing unit of eyes is the
photoreceptor cell, a specialized cell containing two types of molecules bound to each other and located in a membrane: the
opsin, a light-sensitive
protein; and a
chromophore, the
pigment that absorbs light. Groups of such cells are termed "eyespots", and have evolved independently somewhere between 40 and 65 times. These eyespots permit animals to gain only a basic sense of the direction and intensity of light, but not enough to discriminate an object from its surroundings.
[22] "
"
A
photoreceptor cell is a specialized type of
neuroepithelial cell found in the
retina that is capable of
visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible
electromagnetic radiation) into signals that can stimulate biological processes. To be more specific,
photoreceptor proteins in the cell absorb
photons, triggering a change in the cell's
membrane potential. "
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