AP BIOLOGY

Detailed explanation-1: -RuBP. RuBP (ribulose 1, 5-biphosphate) is a five-carbon sugar which reacts with CO2 in the first step of the Calvin cycle for fixing carbon in photosynthetic systems. That reaction is catalyzed by the large enzyme rubisco .

Detailed explanation-2: -The reactions of the Calvin cycle add carbon (from carbon dioxide in the atmosphere) to a simple five-carbon molecule called RuBP. These reactions use chemical energy from NADPH and ATP that were produced in the light reactions.

Detailed explanation-3: -During the carbon fixation stage of the light-independent reaction or the Calvin cycle, one molecule of carbon dioxide binds with the five-carbon molecule ribulose biphosphate through the action of the enzyme ribulose biphosphate carboxylase (rubisco).

Detailed explanation-4: -Ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO) is the key enzyme involved in photosynthetic carbon fixation, as it catalyzes the conversion of atmospheric CO2 into organic compounds.

Detailed explanation-5: -The Calvin cycle reactions can be divided into three main stages: carbon fixation, reduction, and regeneration of the starting molecule.