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Introduction to Photosynthesis

• Through the process of photosynthesis, plants and other phototrophs capture the sun’s energy and transform carbon dioxide into energy-rich foods. In higher organisms like plants, these reactions occur in the chloroplast.

• Pigments such as chlorophyll absorb the sun’s 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 made.

• 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 enzyme–catalyzed reactions are coupled to the hydrolysis of ATP.