Question

g - Identify the molecules into three categories: molecules brought in and used in three turns of the Calvin cycle, molecules produced during three turns of the Calvin cycle that leave the cycle, and molecules used and regenerated within the Calvin cycle during three turns. Molecules brought in and used in three turns of the Calvin cycle Molecules produced in three turns of the Calvin cycle that leave the cycle Molecules used and regenerated within the Calvin cycle in three turns

Answer 1

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.