<P> C carbon fixation or the Hatch - Slack pathway is a photosynthetic process in some plants . It is the first step in extracting carbon from carbon dioxide to be able to use it in sugar and other biomolecules . It is one of three known processes for carbon fixation . The C in one of the names refers to the 4 - carbon molecule that is the first product of this type of carbon fixation . </P> <P> C fixation is an elaboration of the more common C carbon fixation and is believed to have evolved more recently . C overcomes the tendency of the enzyme RuBisCO to wastefully fix oxygen rather than carbon dioxide in the process of photorespiration . This is achieved by ensuring that RuBisCO works in an environment where there is a lot of carbon dioxide and very little oxygen . CO is shuttled via malate or aspartate from mesophyll cells to bundle - sheath cells . In these bundle - sheath cells CO is released by decarboxylation of the malate . C4 plants use PEP carboxylase to capture more CO in the mesophyll cells . PEP Carboxylase (3 carbons) binds to CO to make oxaloacetic acid (OAA). The OAA then makes malate (4 carbons). Malate enters bundle sheath cells and releases the CO . These additional steps, however, require more energy in the form of ATP . Using this extra energy, C plants are able to more efficiently fix carbon in drought, high temperatures, and limitations of nitrogen or CO . Since the more common C pathway does not require this extra energy, it is more efficient in the other conditions . </P> <P> The naming Hatch - Slack pathway is in honor of Marshall Davidson Hatch and C.R. Slack, who elucidated it in Australia in 1966 . </P>

Where does carbon fixation occur in c4 plants