Which experimental modification would most effectively help to determine the sequence of reactions and reaction intermediates in the Calvin cycle?

Question

A.  Exposing the cells to 14CO2 for various time intervals
B.  Exposing the cells to alternating periods of light and darkness
C.  Exposing the cells to radiolabeled O2 instead of 14CO2
D.  Varying the amount of water the cells are exposed to

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

  Gather Content
How would you begin to narrow down the experimental options? What key molecules could you focus on considering the investigation is about the Calvin cycle?

  Choose Answer
Do you have all the information needed to determine which experimental approach would be most effective?

  Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  Exposing the cells to 14CO2 for various time intervals


Clarify Question
What is the key concept addressed by the question?
        · The question asks you to determine which experimental modification would most effectively help determine reactions and intermediates in the Calvin cycle.
What type of thinking is required?
        · You are being asked to weigh and judge, or evaluate, the different experimental modifications to determine which approach would be most effective for investigating the Calvin cycle.

  Gather Content
How would you begin to narrow down the experimental options? What key molecules could you focus on considering the investigation is about the Calvin cycle?
        · Recall that photosynthesis is comprised of the light reactions, which produces ATP, NADPH, and oxygen and the Calvin cycle, which produces organic molecules from inorganic carbon dioxide.
        · The first phase of photosynthesis includes the light reactions, where energy from the sun is captured using molecules like chlorophyll to remove electrons from water, excite them to a higher energy level, and to use redox reactions in order to produce ATP and NADPH. The second phase of photosynthesis includes the Calvin cycle, which uses the ATP and NADPH products of the light reactions to fix inorganic carbon into an organic form within chloroplasts.
        · Considering what you know about the Calvin cycle, which experimental options make the most sense?

  Choose Answer
Do you have all the information needed to determine which experimental approach would be most effective?
        · Since this question focuses on the Calvin cycle and not the light reactions, exposing the cells to alternating periods of light and darkness is unlikely to affect the Calvin cycle directly. Likewise, molecules associated with the light reactions like water and oxygen are probably less useful as well. That leaves using a carbon dioxide-based approach as the most effective for determining reactions and reaction intermediates in the Calvin cycle.

  Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · Answering this question correctly depended on your ability to apply what you know about key molecules in both the light reactions and the Calvin cycle to determine which experimental modification would most effectively determine reactions and intermediates in the Calvin cycle.
        · If you got a correct answer, well done! If you got an incorrect answer, were you able to identify the key molecules in each answer? Were you able to use that information to systematically eliminate options that were associated with the light reactions and not the Calvin cycle? Were you able to conclude that the carbon dioxide based experimental modification would be most suitable for investigating the Calvin cycle?