Question

Calvin cycle is also known as ______ pentose phosphate pathway.

• A. Oxidative
• B. Redox
• C. Reductive
• D. Assimilatory

Hint:

Remember:
• Calvin cycle \(\rightarrow\) Carbon fixation pathway
• Location \(\rightarrow\) Chloroplast stroma
• Requires \(\rightarrow\) ATP and NADPH \[ CO_2 + ATP + NADPH \rightarrow \text{Carbohydrate} \]

Answer 1

The Correct Option is C

Concept: The Calvin cycle is the major pathway of carbon fixation in photosynthetic organisms. It occurs in the chloroplast stroma and converts atmospheric carbon dioxide into carbohydrates using ATP and NADPH produced during the light reactions. The Calvin cycle is also called the: \[ \text{Reductive Pentose Phosphate Pathway (RPPP)} \] because carbon dioxide is reduced to carbohydrate during the process.

Step 1: Understanding why the Calvin cycle is called reductive. During the Calvin cycle: \[ CO_2 \rightarrow \text{Carbohydrates} \] This conversion requires:
• ATP as energy source
• NADPH as reducing power Since reduction of carbon dioxide takes place, the pathway is termed: \[ \boxed{\text{Reductive pentose phosphate pathway}} \]

Step 2: Eliminating the incorrect options.
• Option (A): Oxidative pentose phosphate pathway is a different metabolic pathway involved in NADPH generation.
• Option (B): Redox is a general term for oxidation-reduction reactions and is not the accepted name of the Calvin cycle.
• Option (D): Assimilatory refers broadly to nutrient incorporation but is not the standard alternate name of the Calvin cycle. Hence, the correct answer is Reductive. \[ \boxed{\text{Calvin cycle} = \text{Reductive Pentose Phosphate Pathway}} \]