Question

The product of the photorespiration process is:

• A. Phosphoglycerate
• B. Phosphoglycolate
• C. Both A and B
• D. Oxalo acetic acid

Hint:

Recall that RuBisCO's oxygenase reaction splits RuBP into two different fragments, not just one.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks what compound or compounds photorespiration produces when RuBisCO reacts with oxygen instead of carbon dioxide.

Step 2: Key Formula or Approach:
When RuBisCO acts as an oxygenase, it splits the five carbon sugar RuBP using oxygen into one molecule of 3-phosphoglycerate and one molecule of 2-phosphoglycolate.
\[ RuBP + O_2 \rightarrow 3\text{-phosphoglycerate} + 2\text{-phosphoglycolate} \]

Step 3: Detailed Explanation:
Option 1, phosphoglycerate, is indeed one of the two products of this oxygenation reaction, so it is part of the answer but not the whole answer by itself.
Option 2, phosphoglycolate, is the other product formed in the same reaction, it is the two carbon compound that then gets processed further in the peroxisome and mitochondria during the rest of the photorespiratory pathway.
Option 3 says both A and B, and since the single oxygenation step of RuBisCO produces one molecule of each of these two compounds together, this is the fully correct choice.
Option 4, oxaloacetic acid, is a four carbon compound formed when CO2 is fixed by PEP carboxylase in the C4 pathway, it has nothing to do with the photorespiration reaction.

Step 4: Final Answer:
Since photorespiration yields both phosphoglycerate and phosphoglycolate from a single RuBP molecule, option 3, both A and B, is correct.