Evolution of Photoreceptors
This extract was created in the absence of an abstract.
Excerpt
The value of speculation in science is largely a matter of opinion. I believe that it is useful, if only as a catalyst of research. Moreover, it is fun, and as you will observe I shall generously indulge myself here.
EARLIEST PHOTORECEPTORS
Nature's first photoreceptor was presumably a photosynthetic apparatus, at first it might have been macromolecules or granules containing chlorophyll, then vesicles and lamellae coated with the photopigment similar to the chromophores of purple bacteria which are bacteriochlorophyll-containing vesicles or stacks of saccules from the plasma membrane (Gibbs et al., 1965). From such photosynthetic membranes there evolved fully differentiated chloroplasts with lamellar systems. The significance of arrays of membranes, characteristic also of most if not all subsequent photoreceptors, seems clear: to ensure an ordered and piano-arrangement of the molecules of photopigment for the most effective absorption of radiant energy.
I postulate further that after acquiring a photosynthetic apparatus the...
