# Bacteriorhodopsin and color change

**URL:** <https://boards.straightdope.com/t/bacteriorhodopsin-and-color-change/315382>\
**Category:** Factual Questions\
**Created:** [August 3, 2005, 1:22am UTC](https://boards.straightdope.com/t/bacteriorhodopsin-and-color-change/315382 "2005-08-03T01:22:23Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Doobieous](https://avatars.discourse-cdn.com/v4/letter/d/da6949/32.png) [@Doobieous](https://boards.straightdope.com/u/Doobieous)\
**Post date:** [August 3, 2005, 1:22am UTC](https://boards.straightdope.com/t/bacteriorhodopsin-and-color-change/315382/1 "2005-08-03T01:22:23Z")

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On one of my mail lists, someone conjectured instead of chlorophyll for photosynthesis, the plants on a proposed planet using bacteriorhodopsin instead. Now, I know that when halophytic bacteria utilize the rhodopsin, they turn from shades of red and purple to a yellow color, as my understanding of rhodopsin is that it changes from purple to yellow as it’s working. We wondered, if a plant were to use rhodopsin for photosynthesis (or at least metabolization), would this mean the rhodopsin would be yellow during the day, and purple at night?