Questions: In which cell of the accompanying figure would elevated oxygen concentrations have the greatest inhibitory effect on carbon fixation reactions?
cell I only
cell II only
neither cell I nor cell II
both cell I and cell II
Transcript text: In which cell of the accompanying figure would elevated oxygen concentrations have the greatest inhibitory effect on carbon fixation reactions?
cell I only
cell II only
neither cell I nor cell II
both cell I and cell II
Solution
The answer is: cell II only.
Explanation:
Cell I: This cell is likely a C4 plant cell, which has a mechanism to concentrate CO2 in bundle sheath cells, reducing the inhibitory effect of oxygen on carbon fixation. Therefore, elevated oxygen concentrations would not have a significant inhibitory effect on carbon fixation in cell I.
Cell II: This cell is likely a C3 plant cell, where the enzyme Rubisco directly fixes CO2 in the Calvin cycle. Rubisco is known to have a dual affinity for both CO2 and O2. Elevated oxygen concentrations can lead to photorespiration, where Rubisco fixes O2 instead of CO2, thus inhibiting carbon fixation. Therefore, elevated oxygen concentrations would have a significant inhibitory effect on carbon fixation in cell II.
Neither cell I nor cell II: This option is incorrect because elevated oxygen concentrations do affect carbon fixation in cell II.
Both cell I and cell II: This option is incorrect because elevated oxygen concentrations do not significantly affect carbon fixation in cell I.
In summary, elevated oxygen concentrations have the greatest inhibitory effect on carbon fixation reactions in cell II only.