Question

Operation of C2 oxidative photosynthetic cycle involves the cooperative interaction among three cellular organelles, namely,

• A. Chloroplast, Mitochondria and Nucleus
• B. Chloroplast, Mitochondria and Golgi body
• C. Chloroplast, Mitochondria and Peroxisome
• D. Chloroplast, Mitochondria and Vacuole

Hint:

Mnemonic: "C-P-M" (Chloroplast $\rightarrow$ Peroxisome $\rightarrow$ Mitochondria).
Remember that photorespiration is a light-dependent release of \(CO_2\) and uptake of \(O_2\).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The "C2 oxidative photosynthetic cycle" is another name for Photorespiration. The question asks for the three specific organelles that must work together to complete this pathway.
Detailed Explanation:

• The C2 Cycle Process:
Photorespiration occurs when the enzyme RuBisCO binds with Oxygen (\(O_2\)) instead of Carbon Dioxide (\(CO_2\)).
This produces one molecule of 3-PGA and one molecule of a 2-carbon compound, Phosphoglycolate.

• Organelle Cooperation:
The 2-carbon compound must be "recycled" back into the Calvin cycle through a complex series of reactions involving three organelles in a specific sequence:
1. Chloroplast: RuBP + \(O_2\) $\rightarrow$ Phosphoglycolate. Glycolate is then transported out.
2. Peroxisome: Glycolate is converted to Glyoxylate and then to the amino acid Glycine. Hydrogen peroxide is also managed here.
3. Mitochondria: Two molecules of Glycine are converted into one molecule of Serine, releasing \(CO_2\) and ammonia in the process.
The Serine then travels back through the peroxisome to the chloroplast to be converted back to 3-PGA.

• Significance:
This process is considered wasteful as it loses fixed carbon and consumes energy (ATP and NADPH), which is why \(C_4\) plants evolved mechanisms to avoid it.

Step 2: Final Answer:
The C2 cycle involves the Chloroplast, Peroxisome, and Mitochondria.