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Unformatted text preview: hase 2 of the Calvin cycle?
The G3Ps are us ed in Phas e 3 to regenerate the RuBP molec ules us ed in Phas e 1.
The G3Ps are needed to abs orb the CO2 that was tak en up in Phas e 1.
The G3Ps are needed for reac tions that us e up the ex tra ATP and NADPH produc ed by the light reac tions , k eeping thes e molec ules
from ac c umulating in the c ell. ANSWER: Correct
Counting c arbons —k eeping trac k of where the c arbon atoms go in eac h reac tion—is a s imple way to help unders tand what is happening in the
Calv in c y c le.
To produc e 1 molec ule of G3P (whic h c ontains 3 c arbons ), the Calv in c y c le mus t tak e up 3 molec ules of CO2 (1 c arbon atom eac h).
The 3 CO2 molec ules are added to 3 RuBP molec ules (whic h c ontain 15 total c arbon atoms ), nex t produc ing 6 molec ules of 3PGA
(18 total c arbon atoms ).
In reduc ing 3PGA to G3P (Phas e 2), there is no addition or remov al of c arbon atoms .
At the end of Phas e 2, 1 of the 6 G3P molec ules is output from the c y c le, remov ing 3 of the 18 c arbons .
The remaining 5 G3P molec ules (15 total c arbon atoms ) enter Phas e 3, where they are c onv erted to 3 molec ules of R5P.
Finally , the R5P is c onv erted to RuBP without the addition or los s of c arbon atoms . Part B Quantifying the inputs of AT P and NADPH and output of Pi
The Calv in c y c le depends on inputs of c hemic al energy (ATP) and reduc tant (NADPH) from the light reac tions to power the c onv ers ion of CO2 into
G3P. In this ex erc is e, c ons ider the net c onv ers ion of 3 molec ules of CO2 into 1 molec ule of G3P.
Drag the labels to the appropriate targets to indicate the num bers of m olecules of ATP/ADP, NADPH/NADP+, and Pi (inorganic phosphate se ssion.ma ste r ingbiology.c om/myc t/a ssignme ntPr intVie w? a ssignme ntI D= 2242937 33/41 13- 10- 13 Cha pte r 10 groups) that are input to or output from the Calvin cycle.
Labels can be used once, m ore than once, or not at all. Hin t 1. Parallels between glycolysis and Phase 2 of the Calvin cycle
The reac tions of Phas e 2 of the Calv in c y c le are identic al to s ev eral of the reac tions in gly c oly s is (the firs t s tage of c ellular res piration), e...
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