Question

Given below are two statements
Statement I: The light-dependent reactions occur in the stroma in presence of light
Statement II: The light-independent reactions occur in the thylakoid in the absence of light
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Think "L" for Light and "L" for Lamellae/Thylakoids.
Think "S" for Stroma and "S" for Synthesis (Glucose synthesis).
This simple mnemonic helps remember the correct locations of these critical biochemical pathways.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question examines the two main phases of photosynthesis: the photochemical phase (light reactions) and the biosynthetic phase (dark or light-independent reactions), focusing specifically on their locations within the chloroplast and their light requirements.

Step 2: Detailed Explanation:

• Analysis of Statement I:
Light-dependent reactions (Photolysis of water, ATP, and NADPH formation) take place in the thylakoid membranes (grana) of the chloroplast.
The enzymes and pigments (like chlorophyll) required for light absorption are embedded in these membranes.
The statement claims they occur in the stroma, which is factually incorrect.

• Analysis of Statement II:
Light-independent reactions (Calvin cycle/CO\( _2 \) fixation) take place in the stroma of the chloroplast.
These reactions use the ATP and NADPH produced by the light reactions to convert CO\( _2 \) into glucose.
The statement claims they occur in the thylakoids, which is incorrect.
Furthermore, the term "in the absence of light" is misleading. While they do not directly require light photons, they depend on the products of light reactions and many Calvin cycle enzymes (like Rubisco) are light-activated. They typically happen during the day.
Final Answer:
Since Statement I lists the wrong location (stroma instead of thylakoid) and Statement II lists the wrong location (thylakoid instead of stroma) and implies a requirement for darkness, both statements are incorrect.
Thus, option (B) is the most appropriate answer.