Cytochrome Oxidase, Topoisomerases, Cohesins, PCNA Functions

Q.2 Match List I with List II LIST I (Enzyme) LIST II (Function) A. Cytochrome oxidase I. Electron transport system B. Topoisomerases II. Change linking number C. Cohesins III. DNA Replication D. PCNA IV. Cell cycle Choose the correct answer from the options given below: (A) - (I), (B) - (II), (C) - (III), (D) - (IV) (A) - (I), (B) - (III), (C) - (II), (D) - (IV) (A) - (I), (B) - (II), (C) - (IV), (D) - (III) (A) - (III), (B) - (IV), (C) - (I), (D) - (II) Options: 68019147805. 1 68019147806. 2 68019147807. 3 68019147808. 4

Q.2 Match List I with List II

LIST I (Enzyme) LIST II (Function)
A. Cytochrome oxidase I. Electron transport system
B. Topoisomerases II. Change linking number
C. Cohesins III. DNA Replication
D. PCNA IV. Cell cycle

Choose the correct answer from the options given below:

  1. (A) – (I), (B) – (II), (C) – (III), (D) – (IV)
  2. (A) – (I), (B) – (III), (C) – (II), (D) – (IV)
  3. (A) – (I), (B) – (II), (C) – (IV), (D) – (III)
  4. (A) – (III), (B) – (IV), (C) – (I), (D) – (II)

    • Option 1: A-I (correct), B-II (correct), C-III (wrong; cohesins not directly DNA replication), D-IV (wrong; PCNA not cell cycle-specific).

    • Option 2: A-I (correct), B-III (wrong; topoisomerases not replication-exclusive), C-II (wrong), D-IV (wrong).

    • Option 3: A-I (correct), B-II (correct), C-IV (correct), D-III (correct). Matches all functions precisely.​

    • Option 4: A-III (wrong), B-IV (wrong), C-I (wrong), D-II (wrong).

      Cytochrome oxidase is part of the electron transport system, topoisomerases alter DNA linking number, cohesins regulate sister chromatid cohesion in the cell cycle, and PCNA supports DNA replication. The correct matching is option 3: (A)-(I), (B)-(II), (C)-(IV), (D)-(III).​

      Enzyme Functions

      Cytochrome oxidase (Complex IV) transfers electrons to oxygen in the mitochondrial electron transport system, driving ATP synthesis. Topoisomerases relieve DNA supercoiling by changing the linking number during processes like replication. Cohesins hold sister chromatids together until anaphase, essential for proper cell cycle progression. PCNA acts as a sliding clamp, enhancing DNA polymerase processivity in replication.

      Option Analysis

    Cytochrome oxidase, topoisomerases, cohesins, and PCNA are key enzymes in cellular processes like electron transport, DNA topology, cell cycle regulation, and replication. This Match List I with List II guide breaks down their functions for GATE Life Sciences aspirants, explaining every option with biology insights.

    Core Match Explained

    In this Match List I with List II question, Cytochrome oxidase links to Electron transport system (I) as Complex IV in mitochondria. Topoisomerases match Change linking number (II) by resolving DNA supercoils. Cohesins align with Cell cycle (IV) for sister chromatid cohesion during mitosis. PCNA pairs with DNA Replication (III) as a processivity factor.

    Detailed Function Breakdown

    • Cytochrome oxidase: Final ETC enzyme reducing O₂ to H₂O, crucial for oxidative phosphorylation.

    • Topoisomerases: Type I/II enzymes nick/religate DNA strands, altering linking number (Lk = Tw + Wr).

    • Cohesins: SMC proteins form rings holding chromatids; cleaved by separase at anaphase.

    • PCNA: Trimeric clamp loaded by RFC, boosts Pol δ/ε efficiency 1000-fold in S-phase.

    Why Option 3 Wins

    Option 3 perfectly maps A-I, B-II, C-IV, D-III, avoiding mismatches like assigning cohesins to replication (they aid indirectly via cohesion). Other options confuse roles, e.g., Option 1 swaps C and D.​

    GATE Life Sciences Prep Tips

    Focus on enzyme function matching for PYQs. Visualize: ETC chain for cytochrome oxidase; DNA topology for topoisomerases; mitotic spindle for cohesins; replisome for PCNA. Practice similar lists on chromatin remodeling and checkpoints.

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