What happens during carboxylation phase

Answer 1

During the carboxylation phase, carbon dioxide (CO2) is added to a molecule typically with the help of an enzyme called carbonic anhydrase. This process is commonly observed in biological systems, particularly during photosynthesis and in certain metabolic cycles.

In photosynthesis, carboxylation occurs during the light-independent reactions, also known as the Calvin cycle. During this phase, the enzyme RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes the addition of carbon dioxide to a five-carbon molecule called ribulose-1,5-bisphosphate (RuBP). The six-carbon compound formed after carboxylation then quickly breaks down into two molecules of 3-phosphoglycerate (3-PGA), which continues to participate in subsequent reactions of the Calvin cycle.

In metabolic cycles such as the citric acid cycle (also known as the Krebs cycle), carboxylation reactions also take place. For example, one such reaction occurs during the conversion of pyruvate to oxaloacetate. Pyruvate carboxylase catalyzes the addition of carbon dioxide to pyruvate, leading to the formation of oxaloacetate. This carboxylated intermediate then progresses through the cycle, undergoing various transformations and ultimately producing energy-rich molecules such as ATP.

Overall, during the carboxylation phase, carbon dioxide is incorporated into a molecule through enzymatic catalysis, enabling the formation of new compounds and facilitating various biological processes.