13. Which one of the following statements is INCORRECT about the role of oxidative pentose phosphate pathway in plant metabolism?
(1) Generation of NADPH required to drive biosynthetic reactions.
(2) Production of pentose phosphate for the synthesis of nucleic acids.
(3) Formation of erythrose 4-phosphate for biosynthesis of aromatic amino acids.
(4) Production of NADH to generate ATP

Introduction

The oxidative pentose phosphate pathway (OPPP) plays an essential role in plant metabolism by providing reducing power and metabolic intermediates for biosynthetic processes. Understanding the specific functions of this pathway highlights its importance in cellular metabolism and plant physiology.

Explanation of Each Option

(1) Generation of NADPH required to drive biosynthetic reactions.

• Correct. OPPP produces NADPH, essential for reductive biosynthesis such as fatty acid and nucleic acid synthesis.

(2) Production of pentose phosphate for the synthesis of nucleic acids.

• Correct. Pentose phosphates like ribose-5-phosphate generated by OPPP are crucial precursors for nucleotide and nucleic acid synthesis.

(3) Formation of erythrose 4-phosphate for biosynthesis of aromatic amino acids.

• Correct. Erythrose 4-phosphate produced is a key precursor for the shikimate pathway, leading to aromatic amino acids.

(4) Production of NADH to generate ATP.

• Incorrect. The OPPP generates NADPH, not NADH. NADH is mainly produced during glycolysis and the citric acid cycle for ATP synthesis.

Why Option (4) Is Incorrect

NADPH produced in the OPPP serves biosynthetic and antioxidant functions rather than direct energy generation through ATP, which involves NADH in mitochondrial respiration.

This clarification is essential for students studying plant biochemistry and cellular energy dynamics.