Question

Which of the following CORRECTLY describes the role of rubisco in the Calvin cycle?A) Rubisco uses ATP to regenerate RUBP.B) Rubisco incorporates CO2 from the atmosphere into an organic molecule.C) None of the other answer options is correct.D) Rubisco uses NADPH to reduce 3-phosphoglycerate to a three-carbon sugar.

Answer 1

The correct answer is B) Rubisco incorporates CO2 from the atmosphere into an organic molecule

RuBP oxygenase-carboxylase or rubisco enzyme is an enzyme that acts during the first stage of the Calvin cycle (light-independent or dark reactions of photosynthesis). Its role is in the process of carbon fixation where rubisco incorporates carbon dioxide into an organic molecule (CO2 combines with a five-carbon acceptor molecule, ribulose-1,5-bisphosphate – RuBP).

Besides of using CO2 as a substrate, rubisco sometimes uses O2.  This is a reaction called photorespiration, which leads to the loss of already-fixed carbon, waste of energy and decrease in sugar synthesis.