The Question is from neet-botany photosynthesis-in-higher-plants light-phase, and it was created by the author NISHANTH

Question

Under conditions of high light intensity and limited CO2 availability, which process is most likely to be favored in chloroplasts?

NISHANTH · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Photosynthesis and Photorespiration
 **Related Topics**: Light-dependent reactions, Calvin cycle, RuBisCO enzyme
 **Prerequisites**: Understanding of the light-dependent and light-independent reactions of photosynthesis.
## SOLUTION PATHWAY
**Given Information**:
  High light intensity
  Limited CO2 availability
**Method & Steps**:
 1. High light intensity leads to increased production of ATP and NADPH in the light-dependent reactions of photosynthesis.
  Reasoning:  Light energy drives the electron transport chain, generating ATP via photophosphorylation and NADPH.
  Formula/Rule:  No specific formula, but understanding of the light-dependent reactions is crucial.
 2. Limited CO2 availability restricts the Calvin cycle's ability to fix carbon dioxide.
  Working: The Calvin cycle requires CO2 to produce glucose.  With low CO2, this cycle slows down.
  Key Point: RuBisCO, the enzyme responsible for carbon fixation, can bind to oxygen when CO2 is scarce.
 3. Under these conditions, RuBisCO's oxygenase activity is favored, leading to photorespiration.
  Result: Photorespiration is the process where RuBisCO reacts with oxygen instead of CO2, leading to a net loss of carbon.
  Verification:  The conditions given directly point to the limitations of the Calvin cycle and the increased likelihood of RuBisCO binding to oxygen.
 ## OPTION ANALYSIS
A :x: Enhanced Calvin cycle activity is inhibited by limited CO2.
B :x: Increased non-cyclic photophosphorylation is possible, but it doesn't address the CO2 limitation; photorespiration is the primary consequence.
C ✓: Photorespiration is favored because of the low CO2 concentration and high oxygen concentration (a byproduct of the light-dependent reactions).
D :x: Increased chlorophyll synthesis is not a direct response to limited CO2; it's more related to light adaptation.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing photorespiration with photosynthesis: Photorespiration is a wasteful process that competes with carbon fixation.
   How to avoid:  Clearly understand the role of RuBisCO and its dual functionality.
  2.Failing to consider the role of RuBisCO: RuBisCO's oxygenase activity is key to understanding photorespiration.
   How to avoid: Remember RuBisCO's affinity for both CO2 and O2.
 **Quick Tips**:
  1.Remember that photorespiration is a consequence of RuBisCO's affinity for oxygen when CO2 is limited.
  2.High light, low CO2 = photorespiration.

NISHANTH · Answer

Enhanced Calvin cycle activity

NISHANTH · Answer

Increased non-cyclic photophosphorylation

NISHANTH · Answer

The correct Option is "Photorespiration"

NISHANTH · Answer

Increased synthesis of chlorophyll

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