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The process of absorption of light energy by plants and animals and its utilization for biologically important purposes. In plants photoreception plays an essential role in photosynthesis and an important role in orientation. Photoreception in animals is the initial process in vision. See Photosynthesis, Taxis, Vision

The photoreceptors of animals are highly specialized cells or cell groups which are light-sensitive because they contain pigments which are unstable in the presence of light of appropriate wavelengths. These light-sensitive receptor pigments absorb radiant energy and then undergo physicochemical changes, which lead to the initiation of nerve impulses that are conducted to the central nervous system. See Eye (invertebrate), Eye (vertebrate)

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the detection of light by unicellular organisms or by photoreceptors, that is, specialized structures containing light-sensitive pigments.

In photoreception, which is one of the basic photobiological phenomena, light serves as a source of information. In photosynthesis, the energy of light is used to power chemical reactions; in photoreception, it performs a triggering informational function that sets off a complex chain of molecular, membranous, and cellular processes. These processes are responsible for comparatively simple types of photoreception, such as phototropism, or the orientation of sessile animals and plants toward a source of light; phototaxis, or the directed movement of freely moving organisms toward or away from light; and photokinesis, or the undirected increase or decrease in the mobility of an organism in response to changes in the level of light. The most complex and highest form of photoreception is vision; it is effected by special organs, which vary in their degree of perception fidelity.

The study of the evolution and comparative physiology of photoreception is of great interest. In protozoans the primitive photoreceptor system consists of an eyespot and flagellum, that is, a receptor and an effector. In Chlamydomonas the photosensitive eyespot is connected to a chloroplast; in Euglena the eyespot is connected directly to a flagellum. Most invertebrates and some vertebrates, such as certain species of fish and amphibians, have a diffuse sensitivity to light, and photoreceptors are not used. In some species light is perceived through chromatophores, that is, special cellular organelles. Nonspecialized photosensitive elements may be scattered over the body or may be concentrated on the surface or below it.

Visual photoreception is accomplished in photoreceptors. The stigmata and ocelli of protozoans and the ocelli of coelenterates, of flat and segmented worms, and of arthropods can be regarded as the simplest forms of the organ of vision. The structure and function of the photoreceptor system is more complex in mollusks. In the octopus and cuttlefish, for example, the system is comparable to the eye of vertebrates. The highly specialized photoreceptors in the compound eye of arthropods and in the chambered eye of vertebrates form the most developed organs of vision. The primary processes of vision are common to all animals, and they take place in the light-sensitive photoreceptor membrane of the visual cell. The composition and molecular structure of the membrane is essentially identical in vertebrates and invertebrates. The differences are, as a rule, in the methods by which the membranes are packed in the light-detecting parts of the various photoreceptors. The principal light-sensitive element of the photoreceptor membrane is visual pigment, a typical and well-studied example of which is rhodopsin.

From the point of view of comparative biochemistry, it is of particular interest that retinal, a β-carotene derivative, serves as a chromophore for absolutely all the visual pigments. Moreover, of all the possible isomers, only 11-cis-retinal can be the chromophore part of a visual pigment molecule. Thus, the molecular biochemical principle underlying the photoreceptor mechanism proved to be phylogenetically fixed. The protein part of the visual pigment molecules is species-specific. The specificity of the protein is apparently responsible for the differences in spectral sensitivity of the retinal cones in color vision. The physicochemical mechanism of photoreception is based on complete photoisomerization of retinal from 11-cis-retinal into trans-retiqal. This photoreaction alters the structure of the protein part of the visual pigment molecule and the functional properties of the photoreceptor membrane. As a result, the ions shift in the visual cell, and the rates of some enzymatic reactions may change. The light-induced changes in the visual pigment molecule and photoreceptor membrane ultimately produce in the receptor cell a visual signal, that is, a propagated photoreceptor electric potential.


Prosser, L., and F. Braun. Sravnitei’naia fiziologiia zhivotnykh. Moscow, 1967. Chapter 12. (Translated from English.)
Fiziologiia sensornykh sistem, part 1. (Rukovodstvo po fiziologii.) Leningrad, 1971. Pages 88–119.
Handbook of Sensory Physiology, vol. 7/1–7/2. Berlin, 1972.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The process of absorption of light energy by plants and animals and its utilization for biological functions, such as photosynthesis and vision.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Light detection is believed to occur in sea urchins within photoreceptor cells in the terminal disc region of their motile tube feet, within spines, and across the test (Millot, 1954; Ullrich-Lifter et al., 2011).
Photoreceptor degeneration is an important pathological process in degenerative retinal diseases such as age-related macular degeneration and retinitis pigmentosa.[1],[2] Intense ultraviolet and blue light initiate photoreceptor damage and death.[3],[4],[5] In animal models of light-induced retinal degeneration, the death of the photoreceptor cells is predominantly caused by apoptosis.[6],[7],[8] Inflammatory chemokines are also increased and microglia are activated in the light-stressed retina,[9],[10] and anti-inflammatory measures have been shown to reduce photoreceptor degeneration in the retina.[11],[12]
They are all specified from multipotent retinal progenitor cells (RPCs) during retina development in an ordered fashion that retinal ganglion cells (GC) are born first, followed by photoreceptor cells (PRC), amacrine cells (AC), horizontal cells (HC), and lastly by bipolar cells (BC) and Muller glial cells (MC) (Figure 4(a)) [10, 25].
Most retinal degeneration is hastened by genetic mutations, and the photoreceptor cell death in the process of retinal degeneration is probably evoking the secondary photoreceptor loss.
In conclusion, the results of this study demonstrate that the intravitreal administration of spermidine induces rat RPE cell dysfunction and death, leading to photoreceptor cell degeneration.
Multiple, parallel cellular suicide mechanisms participate in photoreceptor cell death.
Survival of some photoreceptor cells in albino rats following long-term exposure to continuous light.
In histology, macular edema was noted mostly in the outer nuclear layer, causing liquefaction necrosis of photoreceptor cells, and led to population losses and dysfunction of photoreceptor cells in the macular central fovea.
In the brain, LpPerOps1 transcripts are associated with ventral photoreceptor cell bodies that cluster at the brain.
Bilberry extract and lingonberry extract and their active components protect the retina against blue LED light-induced retinal photoreceptor cell damage, according to a 2014 in vitro study.
After passing through the retina they are reflected by the tapetum lucidum and have a second chance of stimulating a photoreceptor cell. You see the effects of this photon 'recycling' when you admire Pearl's beautiful eyes shining at you from the back of your closet at night.