Solution:

RuBisCO and PEPcase are two key enzymes in the C3 and C4 pathways, respectively. In C3 plants, RuBisCO is the predominant carbon dioxide acceptor, whereas, in C4 plants, PEPcase is the primary carbon dioxide acceptor.

RuBisCO’s Function: RUBP Carboxylase Oxygenase is another name for RuBisCO. It has carboxylase and oxygenase activity, as the name implies. Carbon dioxide has a higher affinity for this enzyme than oxygen. In C3 plants, however, some of this enzyme binds to oxygen through a process known as photorespiration. Photorespiration is a wasteful process because it produces no product that is valuable to the plants. Furthermore, it inhibits carbon fixation in C3 plants.

PEPcase’s Function: In C4 plants, this is the principal carbon dioxide acceptor. RuBisCO, on the other hand, is found in these plants. PEPcase binds to carbon dioxide to form oxaloacetic acid, a four-carbon molecule (OAA). Carbon dioxide is formed when OAA is transformed. Finally, carbon dioxide enters the Calvin cycle, resulting in the production of carbohydrates. It’s vital to note that both C3 and C4 plants go through the Calvin Cycle.