KCET 2018 Biology Solved Paper

In the leaf of a C4 plant, two distinct photosynthetic tissues are present—bundle sheath and mesophyll cells, it is called Kranz anatomy. The carbon dioxide that enters the mesophyll cells is accepted by a 3-carbon molecule called phosphoenol pyruvate (PEP). The enzyme phosphoenol pyruvate carboxylase (PEP case) catalyses the carboxylation of PEP to 4-carbon acid oxaloacetic acid. Oxaloacetate is then converted to a similar molecule, malate, that can be transported in to the bundle-sheath cells. Inside the bundle sheath, malate breaks down, releasing a molecule of CO2 .The CO2 is then fixed by rubisco and made into sugars via the Calvin cycle.