alleryStart learning →Of the six molecules made after three turns of the cycle, how many leave and how many stay?
AFive leave and one remains in the cycle
BThree leave and three remain in the cycle
CTwo leave and four remain in the cycle
DOne leaves and five remain in the cycle
Answer & Solution
Correct answer: D. One leaves and five remain in the cycle
1. Each turn makes two molecules of glyceraldehyde 3-phosphate, so three turns make six.
2. One is exported while the remaining five stay in the cycle.
3. Those five are used to regenerate the five-carbon acceptor.
4. Regenerating the acceptor enables the system to prepare for more carbon dioxide to be fixed.
5. The exported molecule goes to the cytoplasm to contribute to other compounds the plant needs.
6. Exporting more than one would starve the cycle of the acceptor it must rebuild.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 8 "Photosynthesis", section 8.3 Using Light Energy to Make Organic Molecules_
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