[Campbell Biology P.245] Which of the following describes the correct sequence of energy tra... | Practice Question

Which of the following describes the correct sequence of energy transfer within a photosystem after a photon is absorbed?

  • A: Photon → Reaction-center complex → Light-harvesting complex → Primary electron acceptor
  • B: Photon → Pigment molecule in light-harvesting complex → Special pair of chlorophyll a in reaction-center → Primary electron acceptor
  • C: Photon → Primary electron acceptor → Light-harvesting complex → Reaction-center chlorophyll a
  • D: Photon → Reaction-center chlorophyll a → Light-harvesting complex → Primary electron acceptor

Explanation

As described in the text and illustrated in Figure 10.12a, when a photon strikes a pigment molecule in a light-harvesting complex, the energy is passed from molecule to molecule within the light-harvesting complex. This energy then reaches the special pair of chlorophyll a molecules in the reaction-center complex, from which an excited electron is transferred to the primary electron acceptor. Thus, the correct sequence is Photon → Pigment molecule in light-harvesting complex → Special pair of chlorophyll a in reaction-center → Primary electron acceptor.