What is Photosynthesis? by Govindjee and Rajni Govindjee
Photosynthesis converts massive amount of Sunlight into
electrical and then chemical energy. The input is carbon dioxide
(CO2), water (H 2O), minerals and light, and the output is
carbohydrates (food) that we need for our nourishment, and
oxygen that we need to breathe [Ref. 1] This oxygenic
photosynthesis occurs in higher plants (e.g., rice, maize,
wheat, mosses, ferns, forest trees, shrubs, etc); in green, red,
brown and yellow algae, and even blue-green cyanobacteria. There
are photosynthetic bacteria (e.g., purple and green bacteria;
and heliobacteria) that can produce carbohydrate (food), but no
oxygen. They are called anoxygenic photosynthesizers. Instead of
the all-abundant water, they use H2S or even organic matter.
Oxygenic photosynthesizers use the green pigment Chlorophyll a,
located in protein complexes in photosynthetic membranes, to run
the photochemistry of the process, whereas the anoxygenic
photosynthesizers use Bacteriochlorophyll inst