Page 175 - Photosynthesis: The Green Miracle

Harun Yahya

The Light Phase

In the first stage of photosynthesis, NADPH and ATP products to be
used as fuel are obtained.
The antenna groups that serve during the first stage of photosynthe-
sis and are responsible for trapping the light are of the greatest impor-
tance. As you have seen, these chloroplasts consist of pigments such as
chlorophyll, protein and fat and contain what are called photosystems.
Photosystem II is stimulated at light wavelengths of 680 nanometers and
less, and Photosystem I is stimulated at 700 nanometers and above. The

chlorophyll molecules that trap specific wavelengths in the photosystems
are known as P680 and P700.
The reactions initiated under the effect of light take place inside these
photosystems. Although each photosystem performs a different process
with the light energy that it traps, the two systems constitute a single
chain reaction and are mutually complementary. The energy caught by
Photosystem II enables hydrogen and oxygen to be released by breaking

down the water molecule. Photosystem I permits NADP to be reduced
with hydrogen.
In this three-stage process, the electrons in water are first carried to
Photosystem II, then from Photosystem II to Photosystem I, and finally to
the NADP. The first stage is exceedingly important, which takes place
when a single photon strikes the plant’s leaf.
The moment a photon strikes the plant, it initiates a chemical reac-
tion, reaching that chlorophyll pigment in the Photosystem II reaction
center and stimulating one of that molecule’s electrons, raising it to a

higher energy level. Electrons are exceedingly small particles that revolve
in specific orbits around the atomic nucleus and bear a very low negative
electrical charge. The light energy pushes the electrons in chlorophyll and
other light-trapping pigments out of their orbits—an initial reaction that
sets up the remaining stages of photosynthesis. At this point the electrons

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