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Title: Can anyone explain photokenisis in Euglena? Why do they speed up in the light? Post by: decadidymus Val on Jun 5, 2017 Hi there. I am currently working on a discussion paper about the effects that light has on Euglena gracilis. One of my observations were that the Euglena who were exposed to light moved faster than those who were kept in the dark. I have put this down to photokenisis. I got that far, however I have not found any sources that explain photokenisis in Euglena. What causes them to move faster in the light? And what is the mechanism behind this? If you could answer with a source that would be very much appreciated! :) Kind regards, Sam *I know this is an odd place to post this question, but for some reason I can't post t anywhere else Title: Re: Can anyone explain photokenisis in Euglena? Why do they speed up in the light? Post by: puzzlebox on Jun 6, 2017 I don't think that's the correct explanation. That's related to plants, I think. I've never heard it described for protists.
Title: Re: Can anyone explain photokenisis in Euglena? Why do they speed up in the light? Post by: habiba on Jun 6, 2017 Euglenas are protists that are autotrophic. These means that they produce their own food. In order to do this, they must use photosynthesis. Therefore, euglena have light sensitive receptors in order to know where to move to carry out photosynthesis.
Title: Re: Can anyone explain photokenisis in Euglena? Why do they speed up in the light? Post by: bio_man on Jun 6, 2017 Correct, it has to do with their photoreceptor.
The eyespot apparatus is a photoreceptive organelle found in the flagellate or (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids. It allows the cells to sense light direction and intensity and respond to it by swimming either towards the light ( A related response occurs when cells are briefly exposed to high light intensity, causing the cell to stop, briefly swim backwards, then change swimming direction. Eyespot-mediated light perception helps the cells in finding an environment with optimal light conditions for photosynthesis. Eyespots are the simplest and most common "eyes" found in nature, composed of photoreceptors and areas of bright orange-red pigment granules. Signals relayed from the eyespot photoreceptors result in alteration of the beating pattern of the flagella, generating a phototactic response. The Euglena photoreceptor was identified as a blue-light-activated adenylyl cyclase. Excitation of this receptor protein results in the formation of cyclic adenosine monophosphate (cAMP) as a second messenger. Chemical signal transduction ultimately triggers changes in flagellar beat patterns and cell movement. Source: https://en.wikipedia.org/wiki/Eyespot_apparatus |