5. During the operation of C2 oxidative photosynthetic cycle, which of the following metabolites is transported from chloroplast to peroxisome?
(1) Glycerate              (2) Serine
(3) Glycine                 (4) Glycolate

Introduction

The C2 oxidative photosynthetic cycle or photorespiration involves metabolite shuttle between chloroplasts, peroxisomes, and mitochondria. Identifying the metabolite transported from chloroplast to peroxisome is essential to understanding this metabolic pathway.

Explanation of Each Option

(1) Glycerate

• Glycerate is synthesized in peroxisomes and transported to chloroplasts, hence not transported from chloroplast to peroxisome.

(2) Serine

• Serine is formed in mitochondria and transported to peroxisomes, not from chloroplast.

(3) Glycine

• Glycine is formed in peroxisomes and transported to mitochondria, not from chloroplast.

(4) Glycolate

• Correct. Glycolate is produced in chloroplasts when Rubisco oxygenates ribulose bisphosphate, and it is transported to peroxisomes for conversion to glyoxylate.

Why Glycolate Is Correct

Glycolate is the first metabolite exported from the chloroplast during photorespiration. It links chloroplast metabolism with peroxisomal function by serving as the entry metabolite into the photorespiratory pathway in peroxisomes.

Understanding this transport step clarifies the compartmentalized flow of metabolites in the photorespiratory cycle, critical for plant physiology and stress biology.