Question

Match List I with List II

Choose the correct answer from the options given below:

• A. A-I, B-IV, C-III, D-V
• B. A-I, B-II, C-IV, D-V
• C. A-V, B-IV, C-III, D-I
• D. A-V, B-II, C-III, D-I

Hint:

Mnemonic for Photosystem Location:
Stacked = PS II (Think S for Second/Stacked).
Non-stacked = PS I (Think N for non-stacked/First).
Spatial separation allows the plant to regulate energy distribution between the two systems efficiently.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to match components of the photosynthetic light reactions (Z-scheme) with their specific structural or functional characteristics.

Step 2: Detailed Explanation:

• Plastocyanin (A): This is a small, water-soluble copper-containing protein found in the thylakoid lumen. It transfers electrons from the Cytochrome $b_6f$ complex to PS I. This is functionally identical to how Cytochrome $c$ works in mitochondria. Therefore, A matches with I.

• Photosystem I (B): PS I complexes are large and bulky; they are excluded from the tightly packed regions of the thylakoids and are found in the stroma lamellae and the edges of the grana (non-stacked regions). Therefore, B matches with II.

• Photosystem II (C): PS II is concentrated in the appressed (stacked) regions of the grana thylakoids. This spatial separation from PS I prevents energy transfer interference. Therefore, C matches with IV.

• Plastoquinone (D): Unlike the proteins in the chain, Plastoquinone is a small hydrophobic molecule (similar to Ubiquinone) that moves freely within the lipid bilayer. It is a non-protein mobile carrier. Therefore, D matches with V.

• Note on III: The Cytochrome $b_6f$ complex (not listed here) is the one that resembles mitochondrial Complex III.

Step 3: Final Answer:
The correct matching is: Plastocyanin-I, PS I-II, PS II-IV, and Plastoquinone-V.