Photosynthesis

Key facts and history

Jan Ingenhousz, a Dutch physician, demonstrated that sunlight was necessary for photosynthesis and that only the green parts of plants could release oxygen.^[1] By the middle of the nineteenth century, scientists knew that plants could use light energy to make carbohydrates from CO2 and water.^[1] In the 1930s, Cornelis van Niel proposed the general equation of photosynthesis that applies to plants, algae, and photosynthetic bacteria.^[1] Van Niel concluded that photosynthesis depends on electron donation and acceptor reactions and that the O2 released comes from the oxidation of water.^[1]

L.N.M. Duysens showed that the primary photochemical reaction of photosynthesis is an oxidation/reduction reaction occurring in a protein complex called the reaction center.^[1] Cyanobacteria evolved later; the surplus oxygen they generated was a direct cause of the Earth's oxygenation.^[2]

What the research sources say

The same authors note that photosynthesis has a profound impact on the earth's atmosphere and climate, even though it occurs in cells or organelles only a few microns across.^[1] Historically, the term photosynthesis has been applied to organisms that depend on chlorophyll or bacteriochlorophyll for converting light energy into chemical free energy.^[1] In oxygenic photosynthesis, water is oxidized by the photosystem II reaction center, a multisubunit protein located in the photosynthetic membrane.^[1]