If the Calvin cycle uses three molecules of CO2 to produce six molecules of G3P (glyceraldehydes-3-phosphate), but only one G3P molecule is used to form a carbohydrate molecule, what happens to the other G3P that were formed?

The other recycled to regenerate RUBP

Explanation:

In Calvin cycle 3 molecule CO2 is needed which combines with 3 molecules of acceptor molecule called RUBP to generate 6 molecules of glyceraldehyde - 3 - phosphate. Out of this these 6 molecules of G3P one molecule removed out of Calvin cycle to form glucose and the rest of the G3P are recycled and regenerates the RUBP acceptor molecule.

To make one molecule of G3P three Calvin cycle turns are needed and one glucose molecule requires 2 G3P molecule therefore 6 turns is required to make one molecule of glucose.

So the out of 6 G3P molecule one exit the cycle to make glucose and other 5 gets recycled.