Answer:
-molecules brought in and used in three turns of the Calvin cycle: Carbon dioxide (CO2)
-molecules produced during three turns of the Calvin cycle that leave the cycle: Glyceraldehyde-3-phosphate (G3P)
-molecules used and regenerated within the Calvin cycle during three turns: Ribulose-1,5-bisphosphate (RUBP)
Explanation:
Calvin cycle is the second phase of photosynthesis, also called the light independent phase. This phase occurs in there major stages namely:
1). Carbon fixation: A molecule of carbon dioxide (CO2), which enters through the stomata of the leaves, is fixed in THREE TURNS i.e. 3CO2 by reacting with a CO2 acceptor called ribulosebiphosphate (RUBP) as catalyzed by RUBISCO. This reaction forms an unstable 6-carbon compound that breaks into 2 molecules of 3-phosphoglycerate (PGA).
2) Reduction: In this stage, the PGA is reduced and phosphorylated by NADPH and ATP respectively to form 6 Glyceraldehyde-3-phosphate (G3P) molecules. One of these G3P molecules leaves the cycle during its THREE TURNS to be used to produce a molecule of glucose. The remaining 5 G3P molecules is used for the third stage.
3). Regeneration: In this stage, the RUBP (CO2 acceptor) is regenerated in THREE TURNS by rearranging the 5 G3P molecules to form 3 RUBP molecules. That is, 3 RUBP to accept 3CO2.
Note: The emphasized THREE TURNS is what must occur in order for one G3P to leave the cycle.
