Photosynthesis Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting
Fractionation of carbon isotopes in oxygenic photosynthesis be less fractionated in C (ie, δC is relatively less negative) compared to C3 plants with low water-use efficiency. C4 plants have developed the C4 carbon fixation pathway to conserve water loss, thus are more prevalent in hot, sunny, and dry climates. These plants differ from C3 plants because the Calvin Cycle in C4 plants produces a four-carbon molecule, malate (rather than 3-phosphoglycerate), after fixation of CO. Malate, the four-carbon compound is the namesake of "C4" photosynthesis. This pathway allows C4 photosynthesis to efficiently shuttle CO to the RuBisCO enzyme and maintain high concentrations of CO within bundle sheath cells.