A rhodopsin molecule in the cell membrane. Retinal is shown in orange

Rhodopsin, also known as visual purple, is a vertebrate photoreceptor protein. It is a pigment of the retina that is responsible for the first events in the perception of light. Rhodopsins belong to the class of G-protein coupled receptors. There exist variants of rhodopsin that are sensitive for different wavelengths of light, the photopsins. Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Photoreceptors are light-sensitive proteins involved in the function of photoreceptor cells. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In biology, pigment is any material resulting in color in plant or animal cells which is the result of selective absorption. ... Human eye cross-sectional view. ... In cell biology, G-protein-coupled receptors, also known as GPCR, seven transmembrane receptors, heptahelical receptors, or 7TM receptors, are a class of transmembrane receptors. ... The wavelength is the distance between repeating units of a wave pattern. ... Categories: Cell biology stubs | G protein coupled receptors | Sensory receptors ...

Rhodopsin consists of two building blocks, an opsin protein called scotopsin and a reversibly covalently bound cofactor, retinal (retinaldehyde). Retinal derives from Vitamin A and is made in the retina. Isomerization of 11-cis-retinal into 11-trans-retinal by light induces a conformational change in rhodopsin that activates the associated G protein and triggers a second messenger cascade. Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... A cofactor is the following: In mathematics a cofactor is the minor of an element of a square matrix. ... The Retinenes (Retinene1 and Retinene2) are chemical derivatives of the dietary supplement vitamin A (see retinol) formed through oxidation reactions. ... Retinol, the dietary form of vitamin A, is a fat-soluble, antioxidant vitamin important in vision and bone growth. ... Human eye cross-sectional view. ... In chemistry, isomerization is the transformation of a molecule into a different isomer. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... In biology, second messengers are low-weight diffusible molecules that are used in signal transduction to relay a signal within a cell. ...

Rhodopsin of the rods most strongly absorbs green-blue light and therefore appears reddish-purple, which is why it is also called "visual purple". It is responsible for the monochromatic vision in the dark. Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ...

Several closely related opsins, the photopsins, exist that differ only in a few amino acids and in the wavelengths of light that they absorb most strongly. These pigments are found in the different types of the cone cells of the retina and are the basis of color vision. Humans have three different other opsins beside rhodopsin, with absorption maxima for yellowish-green (photopsin I), green (photopsin II), and bluish-violet (photopsin III) light. In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... The wavelength is the distance between repeating units of a wave pattern. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina which only function in relatively bright light. ... Color vision is a psychophysical phenomenon that exists only in our minds. ...

Some archaea-bacteria express a proton pump called bacteriorhodopsin to carry out photosynthesis. An alga is known to have an opsin that contains its own monolithic light-gated ion channel, channelrhodopsin-2. Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota The Archaea are a major group of prokaryotes. ... A proton pump is an integral membrane protein that is capable of moving protons across the membrane of a cell, mitochondrion, or other subcellular compartment, thereby creating a difference or gradient in both pH and electrical charge (ignoring differences in buffer capacity) and tending to establish an electrochemical potential. ... Bacteriorhodopsin is a photosynthetic pigment used by archaea, most notably halobacteria. ... Leaf. ... Channelrhodopsin-2 (ChR2) is a unique protein, in that it is an ion channel that is directly opened by light. ...

Normalised absorption spectra of human rhodopsin (dashed) and the three photopsins.

Spectral absorption curves of the short (S), medium (M) and long (L) wavelength pigments in human cone and rod (R) cells. ... Spectral absorption curves of the short (S), medium (M) and long (L) wavelength pigments in human cone and rod (R) cells. ...

See also

• Photopsins, the pigments for color vision.

Categories: Cell biology stubs | G protein coupled receptors | Sensory receptors ...

External links

• Rhodopsin and the eye (http://www.chm.bris.ac.uk/webprojects2003/rogers/998/Rhoeye.htm), an excellent summary with pictures.
• Advanced Light And Vision Concepts (http://wolfstone.halloweenhost.com/TechBase/litadv_AdvancedLightingConcept.html), an extensive overview.