# DAT Q Vault Question

Discussion in 'DAT Discussions' started by jwnichols21, Sep 1, 2011.

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1. ### jwnichols21 5+ Year Member

272
2
Aug 11, 2010
Hey guys,

I can't seem to wrap my head around this question. I thought that 12 ATP were used to create 12 G3P, which split up to yield 10 G3P re-entering the cycle and 2G3P going on to make Glucose. Where do they get "To produce a single 3-carbon G3P molecule a net total of 9 ATP, 3 CO2, and 6 NADPH must be consumed?" Thanks!

How many molecules of ATP are needed during the Calvin Benson Cycle to produce a disaccharide such as sucrose?
A. 9 ATP.
B. 18 ATP.
C. 27 ATP.
D. [Correct] 36 ATP.
E. 45 ATP.
Explanation
36 molecules of ATP are needed to produce a single disaccharide, such as sucrose, during the Carbon Benson Cycle. To produce a single 3-carbon G3P molecule a net total of 9 ATP, 3 CO2, and 6 NADPH must be consumed during the Calvin Benson Cycle. However, since the disaccharide sucrose contains 12 carbon atoms it should not be surprising that four molecules of G3P are needed for its synthesis. Therefore, 4 G3P/sucrose X 9 ATP/G3P = 36 ATP/sucrose.

3. ### predental89 7+ Year Member

246
0
Jun 1, 2008
In the calvin cycle you are probably looking at it when it shows 6 CO2's going into it... because that consumes 18 ATP and 12 NADPH but that makes 2 G3P molecules...So in order to make 1 G3P you should half all of those numbers to get 9 ATP and 6 NADPH.

4. ### NOORALLAH

48
1
Jul 29, 2011
Okay so here is what I think happens!
The first main step in the calvin cycle is the formation of 3carbon sugar called PGAL
6CO2 + 6 RuBP (6 carbon sugar) goes to make 12PGAL (3 carbon sugar)
To do that, we need 12 ATPs
out of the 12 PGALs, we only use 2 and the rest gets recyled in the cycle
recycling cost us 6 more ATP
SO all in all, we need 6+12 to make 2 PGAL or 1 Glucose
To make a disacchride, we would need 18*2= 36 ATPs

5. ### jwnichols21 5+ Year Member

272
2
Aug 11, 2010
Thank you good sir. moment..