How many molecules of atp are needed for each "turn" of the calvin cycle

3 ATP

Explanation:

Each turn of the Calvin cycle also uses up 3 ATP and 2 NADPH in the processes of reducing (adding electrons to) 3-phosphoglyceric acid to produce glyceraldehyde-3 phosphate, and regenerating RuBP so that they can accept a new atom of carbon from CO2 from the air.

9 molecules

*EXPLANATION*

the calvin cycle: three molecules of CO² fixed give a net yield of one molecule of glyceraldehyde 3-phosphat at the net cost of nine molecules of ATP and six molecules of NADPH