C4 Cycle (Hatch and Slack Pathway) is a cyclic pathway. The enzymes concerned with the C4 pathway are placed within the Mesophyll cells and Bundle Sheath cells. During this pathway, the plants convert atmospheric CO2 into a four carbon-containing chemical compound. The reaction is mediated by phosphoenolpyruvate carboxylase. After this, aspartic acid and malic acid are formed within the mesophyll cells and transported to the bundle sheath cells within which  the C4 acids break down to release three-carbon molecules and CO2 and further gets converted to phosphoenolpyruvate and complete the cycle.