Since Rubisco can either fix carbon or oxidize RuBP, what condition will be most favorable for glucose production?

Question

A.  moderate temperatures
B.  high temperatures
C.  dry climate
D.  high oxygen environment

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

  Gather Content
What do you already know about RuBP, rubisco, and the Calvin cycle? What other information is related to the question?

  Choose Answer
Do you have all the information needed to determine the most favorable condition for glucose production?

  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.  moderate temperatures

Clarify Question
What is the key concept addressed by the question?
        · The question asks you to determine the most favorable conditions for glucose production given that rubisco can either fix carbon or oxidize RuBP.
What type of thinking is required?
        · You are being asked to weigh and judge, or evaluate, the different environmental conditions to determine which would most favorably produce glucose.

  Gather Content
What do you already know about RuBP, rubisco, and the Calvin cycle? What other information is related to the question?
        · Recall that plants are evolutionarily adapted to particular climates and environments and respond differently depending on whether the environment is hot, dry, or humid. Part of a plant’s ability to physiologically adapt to an environment has to do with how it metabolizes carbon, and what happens to the machinery that fixes carbon when conditions are not optimal.
        · Remember that the molecule that accepts atmospheric carbon during the Calvin cycle is ribulose-1,5-bisphosphate, or RuBP. Remember also that the key enzyme involved in carbon fixation during the Calvin cycle is RuBP carboxylase/oxygenase, or rubisco. This enzyme is key in taking inorganic carbon dioxide from the air and fixing it in an organic molecule, although under less ideal conditions can oxidize RuBP. Considering the different environmental conditions indicated, how might rubisco’s function change?

  Choose Answer
Do you have all the information needed to determine the most favorable condition for glucose production?
        · Let’s take each option and consider it individually to determine the most correct answer. If environmental conditions are hot or dry, the plant will close its stomata in order to prevent water loss, thereby restricting carbon dioxide diffusion into the leaves. Under those conditions, if light were still available, the light reactions would still occur and oxygen levels would increase.
        · Anything that increases the relative level of oxygen will not be favorable for glucose production, as rubisco will favor oxidizing RuBP instead of fixing carbon. As a result, anything that leads to the closing of stomata, or changes the overall level of oxygen will be unfavorable.
        · Conversely, moderate temperatures allow stomata to remain open, and thus allow carbon dioxide to enter the leaves. This is why moderate temperatures are the most favorable condition for glucose production.

  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 evaluate several environmental conditions for which would be most favorable for glucose production, considering that rubisco can fix carbon or oxidize RuBP.
        · If you got the correct answer, excellent! If you got an incorrect answer, were you able to determine what would happen to stomata and rubisco function under high temperatures and dry climate? Were you able to figure out that oxygen levels would increase if stomata were closed during the day? Were you able to infer moderate temperatures would be preferable to any of the other conditions?