photosynthesis
13 Photosynthesis 6 CO2 + 6 H2 O C6 H12 O6 + 6 O2 One of most important reactions in history of life: source of atmospheric O2 ultimately led to aerobic respiration and eukaryotes Responsible for bulk of glucose production Early experiments showed that mass of plant must be derived from substances in the air, not the soil Experiments with isotopes showed that liberated oxygen comes from water Experiments also showed that light is essential but that some reactions e. , reduction of CO2 continue in the dark Plants do two big, important things during photosynthesis: gain energy absorb light and build sugar glucose . Photosynthesis can be divided into two series of chemical reactions: the light lightdependent reactions and the dark light-independent reactions. In light reactions, light is absorbed; in dark reactions, sugar is built. Occurs when plants, algae, and autotrophic bacteria absorb light energy and build glucose.