Fractionation of carbon isotopes in oxygenic photosynthesis the bundle sheath cells. Different forms of CCM in phytoplankton include the active uptake of bicarbonate and CO through the cell membrane, the active transport of inorganic carbon from the cellular membrane to the chloroplasts, and active, unidirectional conversion of CO to bicarbonate. The parameters affecting C fractionation in phytoplankton contribute to "δ"C values between -18 to -25‰. Fractionation of carbon isotopes in oxygenic photosynthesis Photosynthesis converts carbon dioxide to carbohydrates via several metabolic pathways that provide energy to an organism and preferentially react with certain stable isotopes of carbon. The selective enrichment of one stable isotope over another creates
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.