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​The following are certain statements regarding the photorespiration pathway in plants:​​A. The first two-carbon (2C) compound synthesized by the acti
Question

The following are certain statements regarding the photorespiration pathway in plants:

A. The first two-carbon (2C) compound synthesized by the action of Rubisco in the chloroplast is glycolate.
B. Glycolate exits the chloroplast and enters peroxisomes.
C. Glycolate that is synthesized during C₂ cycle enters the chloroplast from mitochondria.
D. Glycine is transported from peroxisomes to mitochondria.

Which one of the following combinations is INCORRECT?​​

A.

A and B only

B.

A and C only

C.

B, C and D

D.

A, C and D

Correct option is B

Explanation-

Photorespiration involves chloroplasts, peroxisomes, and mitochondria. Here's the actual sequence:
  (i)   Rubisco fixes O₂ (instead of CO₂) → produces 3-phosphoglycerate (3-PGA) and 2-phosphoglycolate.
  (ii)  2-phosphoglycolate is converted to glycolate in the chloroplast, which exits to the peroxisome.
  (iii) In peroxisomes: glycolate → glyoxylate → glycine
  (iv) Glycine moves to mitochondria where 2 glycine → 1 serine + CO₂ + NH₃
  (v)  Serine returns to peroxisome → glycerate → goes back to chloroplast

Analyzing  each statement:
Statement A - The first two-carbon (2C) compound synthesized by the action of Rubisco in the chloroplast is glycolate - INCORRECT
Rubisco forms 2-phosphoglycolate, not directly glycolate. Glycolate is formed after dephosphorylation of 2-phosphoglycolate.
Statement B - Glycolate exits the chloroplast and enters peroxisomes  - CORRECT
This is the normal transport route in photorespiration.
Statement C - Glycolate that is synthesized during C₂ cycle enters the chloroplast from mitochondria  - INCORRECT
Glycolate does not come from mitochondria. It is formed in chloroplast, moves to peroxisome, then processed via glycine/serine in mitochondria. Mitochondria handle glycine → serine, not glycolate synthesis.
Statement D - Glycine is transported from peroxisomes to mitochondria  - CORRECT
This is a key step in photorespiration: peroxisomes produce glycine, which is moved to mitochondria.

Final Answer:
Incorrect statements: A and C 

Correct answer - Option b - A and C only

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