Question

The enzyme ribulose bisphosphate carboxylase/oxygenase, or rubisco, fixes carbon dioxide. The carbon dioxide is incorporated into a five‑carbon compound, which is then hydrolyzed to yield two three‑carbon compounds. Arrange the steps of the rubisco carboxylation reaction in order, beginning with the substrate.

1. Rubisco removes a proton from C3 of ribulose-1,5-bisphosphate
2. Substrate
3. Water attacks C3 of the six-carbon beta-keto acid, hydrating it
4. An enediolate intermediate nucleophilically attacks CO2, incorporating it at C2
5. Product
6. The six-carbon molecule splits, yielding two 3-phosphoglycerate molecules

Answer 1

2. Substrate

4. An enediolate intermediate nucleophilically attacks CO2, incorporating it at C2

1. Rubisco removes a proton from C3 of ribulose-1,5-bisphosphate

3. Water attacks C3 of the six-carbon beta-keto acid, hydrating it

6. The six-carbon molecule splits, yielding two 3-phosphoglycerate molecules

5. Product

Step-by-step explanation:

RuBisCO is one of many enzymes in the Calvin cycle. When Rubisco facilitates the attack of CO2 at the C2 carbon of RuBP and subsequent bond cleavage between the C3 and C2 carbon, 2 molecules of glycerate-3-phosphate are formed.