Photochemistry of Vision
Herbert J.A. Dartnall
Springer Science & Business Media, Dec 6, 2012 - Science - 848 pages
Radiation can only affect matter if absorbed by it. Within the broad range of 300-1000 nm, which we call "the visible", light quanta are energetic enough to produce excited electronic states in the atoms and molecules that absorb them. In these states the molecules may have quite different properties from those in their dormant condition, and reactions that would not otherwise occur become possible. About 80 % of the radiant energy emitted by our sun lies in this fertile band, and so long as the sun's surface temperature is maintained at about 6000° C this state of affairs will continue. This and the transparency of our atmosphere and waters have allowed the generation and evolution of life. Before life began the atmosphere probably also transmitted much of the solar short-wave radiation, but with the rise of vegetation a new product - oxygen - appeared and this, by a photochemical reaction in the upper atmosphere, led to the ozone layer that now protects us from the energetic "short-wave" quanta that once, perhaps, took part in the generation of life-molecules. Light is an ideal sensory stimulus. It travels in straight lines at great speed and, consequently, can be made to form an image from which an animal can make "true", continuous and immediate assessments of present and impending events.
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11-cis retinal 3-dehydroretinol ABRAHAMSON absorption acid Amax Biochem Biol bleaching bovine rhodopsin BROWN changes Chem chromophoric chromophoric group circular dichroism colour cone pigments configuration CRESCITELLI curve dark adaptation DARTNALL and LYTHGOE density digitonin droplets effect electron energy extract fishes flash freshwater frog function gecko HARA HUBBARD intermediate iodopsin irradiation isomers KROPF LIEBMAN light maximum measurements membrane metarhodopsin micelles microvilli mole molecular molecule MoRTON MUNZ Nature Lond observed oil-droplets opsin optical OSTROY phospholipid photochemical photolysis photon photopigment photoreceptors photosensitive Physiol POINCELOT polyene porphyropsin prosthetic group protein quantum receptor regeneration retina retinaldehyde retinene retinochrome retinol retinylidene rhabdom rhabdomeres rhodopsin rod outer segments rods and cones Schiff base SCHWANZARA single cones solution species spectral absorbance spectral sensitivity spectrum squid structure studies teleosts temperature thermal ultraviolet vertebrate Vision Res visual cells visual pigments visual purple vitamin vitamin A2 WALD wave wavelength yellow Yosh