Photopigment
Template:Short description Photopigments are unstable pigments that undergo a chemical change when they absorb light. The term is generally applied to the non-protein chromophore moiety of photosensitive chromoproteins, such as the pigments involved in photosynthesis and photoreception. In medical terminology, "photopigment" commonly refers to the photoreceptor proteins of the retina.<ref>Template:Cite book</ref>
Photosynthetic pigmentsEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Photosynthetic pigments convert light into biochemical energy. Examples for photosynthetic pigments are chlorophyll, carotenoids and phycobilins.<ref name="Blankenship">Template:Cite book</ref> These pigments enter a high-energy state upon absorbing a photon which they can release in the form of chemical energy. This can occur via light-driven pumping of ions across a biological membrane (e.g. in the case of the proton pump bacteriorhodopsin) or via excitation and transfer of electrons released by photolysis (e.g. in the photosystems of the thylakoid membranes of plant chloroplasts).<ref name="Blankenship" /> In chloroplasts, the light-driven electron transfer chain in turn drives the pumping of protons across the membrane.<ref name="Blankenship" />
Photoreceptor pigmentsEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} The pigments in photoreceptor proteins either change their conformation or undergo photoreduction when they absorb a photon.<ref name="Lehninger">Template:Cite book</ref> This change in the conformation or redox state of the chromophore then affects the protein conformation or activity and triggers a signal transduction cascade.<ref name="Lehninger" />
Examples of photoreceptor pigments include:<ref>Template:Cite book</ref>
- retinal (in rhodopsin)
- flavin (in cryptochrome)
- bilin (in phytochrome)
Photopigments of the vertebrate retinaEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} In medical terminology, the term photopigment is applied to opsin-type photoreceptor proteins, specifically rhodopsin and photopsins, the photoreceptor proteins in the retinal rods and cones of vertebrates that are responsible for visual perception, but also melanopsin and others.<ref>Template:Cite book</ref>
See alsoEdit
ReferencesEdit
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