But in 1965 Kortschak, Hartt and Burr reported that 4-C containing dicarboxylic acids, […] In c4 pathway, phosphoenol pyruvate is the first acceptor of CO2, while ribulose biphosphate is the second acceptor. For considerable period of time the Calvin cycle as described earlier was thought to be the only photosynthetic reaction sequence operating in higher plants and algae. The image below illustrates the pathway we just described: It is the first step in extracting carbon from carbon dioxide to be able to use it in sugar and other biomolecules. C4 carbon fixation or the Hatch-Slack pathway is a photosynthetic process in some plants. Oxaloacetic add is the first product in c4 pathway. Plants that use the c4 pathway produce a 4-carbon sugar as the first stable molecule. These plants are very efficient in hot, dry climates and make a lot of energy. Figure \(\PageIndex{1}\): The C4 Pathway The C4 pathway is designed to efficiently fix CO2 at low concentrations and plants that use this pathway are known as C4 plants. In c3 pathway, ribulose biphosphate is the first acceptor of CO2. These plants fix CO2 into a four carbon compound (C4) called oxaloacetate. The cycle begins with CO 2 from the atmosphere entering mesophyll cells where it is used to generate oxaloacetate—a four-carbon molecule—from phosphoenolpyruvate (PEP). It is one of three known processes for carbon fixation Thus in C4 plants, C4 carbon fixation has a net added cost of 1 ATP for every CO2 delivered to rubisco; however, C4 plants are less likely to die of dehydration compared to C3 plants in dry conditions. This is a spatial , rather than temporal separation. Overview of C4 Pathway Photosynthesis The Calvin cycle was believed to be the only photosynthetic reaction series operating in higher plants and algae for a significant amount of time. Hence it is called C4 cycle. 3. A C4 plant is a plant that cycles carbon dioxide into four-carbon sugar compounds to enter into the Calvin cycle. Difference between C3 and C4 pathway. This occurs in cells called mesophyll cells. Some plants, like sugar cane and corn, that grow in hot conditions, use an alternative process called the C 4 pathway to fix carbon. 9.7: C4 Pathway and CAM Overview. In c3 pathway, Phosphoglyceric acid is the first product. 1. (a) The CAM pathway fixes CO{eq}_2 {/eq} onto the three-carbon molecule to make the four-carbon molecule at night, when it is cooler and stomata are open. 2. “Classic” C\(_4\) plants drive C\(_4\) pathway in leaf mesophyll cells whereas their C\(_3\) is located in so-called bundle sheath cells. They have their stomata open for shorter periods during the day to stop the lose of off too much H2O because of the hot temperatures. In the C4 cycle the first stable compound is 4 carbon compound, namely oxaloacetic acid. 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