Through the process of
photosynthesis, plants and other phototrophs capture the suns
energy and transform carbon dioxide into energy-rich foods. In
higher organisms like plants, these reactions occur in the
Pigments such as chlorophyll
absorb the suns energy, which is used to transfer electrons from
water to the coenzyme NADP. The oxidation of water produces the
molecular oxygen we need for aerobic metabolism.
The transport of electrons is
coupled to the movement of protons into the thylakoid interior, the
lumen. When the protons spontaneously flow out of the lumen, ATP is
The reduced NADP, NADPH,
transfers electrons to carbon atoms to form sugars such as glucose.
This occurs in the alvin-Benson cycle. Since electron transfer from
NADPH to carbon atoms is nonspontaneous, the enzymecatalyzed
reactions are coupled to the hydrolysis of ATP.