36. The following statements refer to photosystem structure and function involved in light-dependent reaction of photosynthesis:
A. The antenna or light harvesting complex absorbs light energy and transfers it to the reaction centre.
B. The first electron is released from P680 and transferred to Q_A to produce a semiquinone
C. D1, a protein subunit of the plant PS-II core complex is encoded by gene psbD Which one of the following combinations of above statements is INCORRECT?
(1)A and B                   (2) B and C
(3) A and C               (4) Only C

The INCORRECT combination is (2) B and C:

• A. The antenna or light harvesting complex absorbs light energy and transfers it to the reaction centre.
  Correct. The light-harvesting complex (antenna) collects photons and efficiently funnels this energy to the special pair of chlorophylls in the reaction center of each photosystem.​

• B. The first electron is released from P680 and transferred to QA to produce a semiquinone.
  Incorrect. The first electron excited from P680 is actually transferred to pheophytin (Pheo), which then passes it to QA (the primary quinone electron acceptor). The electron does not jump directly from P680 to QA. The sequence is P680* → Pheo → QA.​

• C. D1, a protein subunit of plant PS-II core complex, is encoded by gene psbD.
  Incorrect. The D1 protein is encoded by the psbA gene, not psbD. psbD encodes the D2 protein of PSII.​

Light-Dependent Reaction: Structure and Electron Flow Errors

Introduction

Key phrase: photosystem II PSII antenna light harvesting complex electron flow D1 protein gene

Photosynthesis harnesses protein complexes and precise electron transfer events. Common errors include incorrect gene assignment and misordering of electron flow among carriers within PSII.​

Explanation of Each Statement

• A. Correct. Light-harvesting complexes transfer energy to reaction centers.

• B. Incorrect. The electron from P680 first goes to pheophytin, then to QA.

• C. Incorrect. D1 protein is encoded by psbA, not psbD; psbD encodes D2.

Option Analysis

• (1) A and B: A is correct; B is incorrect.

• (2) B and C: Both B and C are incorrect, making this the correct option for INCORRECT statements.

• (3) A and C: A is correct; C is incorrect.

• (4) Only C: Only C is incorrect; however, B is also incorrect.

Key Facts: PSII Structure, Function, and Genes

• D1 protein: Encoded by psbA, not psbD.​

• P680* electron transfer: Goes first to pheophytin, then to QA, producing a semiquinone at quinone.​

• LHC/antenna: Essential for efficient energy capture and transfer to the reaction center.​