How Does Introducing a Competitive Inhibitor of Rubisco Affect Photosynthesis?

[metalmagik]

Homework Statement

Suppose that a competitive inhibitor of rubisco is introduced into chloroplasts. Which of the following statements is a logical consequence:
(a) The light reactions will slow down, since electron carriers will be scarce.
(b) The light reactions will speed up to drive the Calvin cycle forward.
(c) Photorespiration will occur in the chloroplasts.
(d) The light reactions will slow down, since O2 will be scarce.
(e) The Calvin Cycle will remain unaffected.

Homework Equations

The Attempt at a Solution

At first I thought competitive inhibition would slow down the process of photosynthesis significantly, but now I am not sure. Even so, the answer can either be (a) or (d). Help please! Thank you

 

[chemisttree]

What is ribulose-1,5-bisphosphate carboxylase/oxygenase's role in the chloroplast? Is it an electron carrier or does it modulate the concentration of an electron carrier? Do light reactions speed up in the presence of O₂ or slow down in the absence of O₂?

 

[Blueshift5]

!

I would like to clarify that the introduction of a competitive inhibitor of rubisco into chloroplasts would likely have a negative impact on photosynthesis. Rubisco is a crucial enzyme in the Calvin cycle, which is responsible for the fixation of carbon dioxide into glucose. Therefore, if rubisco is inhibited, the Calvin cycle would not be able to function efficiently, leading to a decrease in the overall rate of photosynthesis.

Based on this, the most logical consequence would be option (b) - the light reactions will speed up to drive the Calvin cycle forward. This is because the light reactions produce ATP and NADPH, which are essential for the Calvin cycle to occur. If the Calvin cycle is inhibited, the light reactions would need to compensate by producing more ATP and NADPH to maintain the overall rate of photosynthesis.

Option (a) and (d) are also possible consequences, as a decrease in rubisco activity could lead to a scarcity of electron carriers (a) or oxygen (d). However, these would not be the most direct or significant consequences of competitive inhibition.

Option (c) is not a logical consequence, as photorespiration occurs when rubisco mistakenly binds to oxygen instead of carbon dioxide. In this case, the inhibition of rubisco would actually decrease the likelihood of photorespiration occurring.

In conclusion, the most logical consequence of introducing a competitive inhibitor of rubisco into chloroplasts would be an increase in the speed of the light reactions to compensate for the inhibited Calvin cycle.