Question

The organelles involved in the process of photorespiration are

• A. Chloroplast, Mitochondria, and Golgybody
• B. Chloroplast, Mitochondria, and Peroxisomes
• C. Chloroplast, Mitochondria, and Nucleus
• D. Chloroplast, Mitochondria, and Vacuole

Hint:

Remember the mnemonic "CPM" (Chloroplast $\to$ Peroxisome $\to$ Mitochondria) representing the exact order of metabolite flow during the first half of the photorespiratory cycle.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) is an energy-consuming pathway triggered when Rubisco acts as an oxygenase rather than a carboxylase under hot, dry conditions.
The processing of the toxic byproduct phosphoglycolate requires a coordinated metabolic pathway across multiple cellular compartments.

Step 2: Detailed Explanation:
The photorespiratory pathway is unique because it requires the cooperative, sequential functioning of three distinct organelles:
1. Chloroplast: Rubisco binds oxygen to RuBP, producing 3-phosphoglycerate and 2-phosphoglycolate.
Phosphoglycolate is dephosphorylated to glycolate, which is transported out of the chloroplast.
2. Peroxisome: Glycolate is imported and oxidized to glyoxylate, producing hydrogen peroxide (which is decomposed by catalase).
Glyoxylate is then transaminated to form glycine, which is exported.
3. Mitochondria: Two molecules of glycine are decarboxylated and deaminated by glycine decarboxylase to form one molecule of serine, releasing \(\text{CO}_2\) and ammonia (\(\text{NH}_3\)).
The serine is then transported back through the peroxisome and chloroplast to be converted back into 3-phosphoglycerate.
Therefore, the three organelles involved in photorespiration are the Chloroplast, Peroxisome, and Mitochondria.

Step 3: Final Answer:
The organelles involved in photorespiration are the Chloroplast, Mitochondria, and Peroxisomes, corresponding to option (B).