AP BIOLOGY

Detailed explanation-1: -CO2 binds to RuBP in the key process called carbon fixation, forming two-three carbon molecules of phosphoglycerate. The enzyme that carries out this reaction is ribulose bisphosphate carboxylase/oxygenase, which is very large with a four-subunit and present in the chloroplast stroma.

Detailed explanation-2: -In stage 1, the enzyme RuBisCO incorporates carbon dioxide into an organic molecule. In stage 2, the organic molecule is reduced. In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue.

Detailed explanation-3: -Biofixation of carbon dioxide (CO2) by microorganisms 15.1, the key step of the Calvin cycle is catalyzed by the enzyme ribulose bisphosphate carboxylase, which fixes a CO2 molecule onto a molecule of ribulose-1, 5-diphosphate (RuBP), resulting in two molecules of glyceric acid-3-phosphate (3PG).

Detailed explanation-4: -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-5: -(a) An enzyme, RuBP carboxylase, catalyzes both the joining of carbon dioxide with RuBP and the joining of oxygen gas with RuBP. The two molecules are alternative substrates that compete with each other for the same active site on the enzyme.