[TML] Alien ecologies

[Bruce Johnson]

On Aug 20, 2008, at 9:40 AM, darby eckles wrote:

>
> So, what I am wondering is: is it possible to have purple  
> photosynthetic plants?  Is it just a matter of the chlorophyl/ 
> whatever processing UV spectrum light or reflect purple based  
> colors, or would it necessitate some completely different system of  
> light usage?

I expect so. On earth some bacterial photosynthesis uses purple  
pigments, but they use H2S as a redox agent, not H2O, so they release  
sulfur instead of oxygen...in fact IIRC, these are obligate anaerobes.  
(but I could be wrong it's been 30 years since my microbiology  
courses..)


See here : <http://www.microbiologyprocedure.com/bacterial-photosynthesis/bacterial-photosynthesis.htm 
 >
>
>
> Also, what minierals have a purple hue?  Amethyst?  Can that be  
> broken down and used by living creatures?
>

The element's hue is not what defines the coloration of the  
phtosynthesis molecule, which are typically organic cage structures  
around a metal atom. Hemoglobin and Chlorophyl have very similar  
active center structures, a porphyrin ring around a metal atom in the  
center, hemoglobin uses iron, and chlorophyll uses magnesium which  
accounts for much of the difference in colors. (the rest of the  
protein in both molecules is QUITE different, though, see the  
wikipedia entry for each)

It's the whole cage + metal structure which along with the oxidation  
state of the metal determines the color of the molecule.

Amethyst appears to be colored violet due to a mixture of trace  
amounts of iron and aluminum. <http://en.wikipedia.org/wiki/Amethyst>

-- 
Bruce Johnson
University of Arizona
College of Pharmacy
Information Technology Group

Institutions do not have opinions, merely customs