Biology 1002B Lecture Notes - Lecture 4: Channelrhodopsin, Photoisomerization, Opsin
17 Jan 2018
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Eyespots: carotenoid granules: globules in the chloroplast, channelrhodopsins: the part that is light sensitive; light-gated ion channel, light opens the gate. From front side, granules can reflect light and light hit channelrhodopsin. From rear side, light is blocked and cannot get to channelrhodopsin. Just like how light that hits back of our head cannot be detected. Phototransduction of eyespot signal: chlamy cells are polarized - inside of membrane is more negative than outside of membrane (voltage across membrane) It does not have ability to absorb red light: for light to be used, light must be absorbed, and this is done by pigments, together, retinal and opsin make channelrhodopsin, which is an example of a photoreceptor. It does not absorb green light so green light passes through: there is no green excited state for chlorophyll. Light is causing a change in shape in retinal (photoisomerization: converting from trans to cis or from cis to trans.
