photosynthesizing

Photosynthesizing is the process by which organisms convert light energy into chemical energy, enabling the synthesis of organic compounds from carbon dioxide and water. In most organisms that photosynthesize, this occurs in chloroplasts (or photosynthetic membranes in bacteria). The primary products are sugars such as glucose, which serve as an energy source and as building blocks for growth. Oxygen is released as a byproduct in oxygenic photosynthesis.

Photosynthesis consists of two linked sets of reactions. Light-dependent reactions occur in the thylakoid membranes of chloroplasts, where pigments such as chlorophyll absorb light, driving electron transport chains that generate ATP and NADPH and split water to release oxygen. The Calvin cycle (light-independent reactions) uses ATP and NADPH to fix atmospheric CO2 into organic molecules, producing glyceraldehyde-3-phosphate that can be converted into glucose and other carbohydrates.

Organisms differ in their photosynthesizing strategies. Most land plants and many algae use C3 photosynthesis, but some use C4 pathways to concentrate CO2 and reduce photorespiration, and many succulent plants use CAM photosynthesis to fix carbon at night. Evolutionarily, photosynthesis transformed Earth's atmosphere and fueled aerobic life by providing oxygen and forming the base of food webs.

The rate of photosynthesizing is influenced by environmental conditions such as light intensity and quality, temperature, carbon dioxide concentration, water availability, and leaf anatomy. Researchers measure photosynthetic rate by tracing oxygen evolution or CO2 uptake, and these measurements help understand plant productivity and ecosystem carbon balance.