Photosynthetic pigments and photosystems Transitional Reasoning Practice

Questions

1. 1.

   A researcher analyzes two mutant strains of a photosynthetic organism to study the distinct roles of photosystem components. Strain 1 lacks accessory pigments (chlorophyll b and carotenoids) but possesses functional reaction centers, while Strain 2 contains a complete light-harvesting antenna complex but has a defective primary electron acceptor in photosystem II that cannot accept electrons. Under white light illumination, both mutant strains show a marked decrease in their rate of oxygen evolution compared to the wild-type organism. Based on the molecular organization and functioning of photosystems, which statement correctly explains the functional limitation present in each mutant strain?

   • A) Strain 1 cannot photolyze water because accessory pigments provide the catalytic electrons needed by the oxygen-evolving complex, while Strain 2 fails because the light-harvesting complex cannot transfer resonance energy to chlorophyll a.
   • B) Strain 1 cannot absorb blue or red wavelengths because only accessory pigments absorb visible light, while Strain 2 accumulates excessive reduced plastoquinone molecules in the thylakoid membrane.
   • C) Strain 1 cannot dissipate heat because reaction centers solely regulate non-photochemical quenching, while Strain 2 fails because primary electron acceptors are required to channel resonance energy between antenna pigments.
   • D) Strain 1 has a severely reduced capacity to harvest photons across various wavelengths to funnel toward P680, while Strain 2 cannot undergo stable photochemical charge separation to initiate electron flow.

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