Question

part b when a pigment molecule in a light - harvesting complex absorbs a photon of light, what happens to its excited - state electron? the excited - state electron is removed and transferred to a nearby pigment molecule, causing the next pigment to enter an excited state. the excited - state electron is passed to electron acceptors p680 or p700. the excited - state electron excites electrons in other pigments around it, so that multiple pigments can send electrons to p680 or p700. the electron falls back to its ground state, while passing its excited - state energy to an electron in a nearby pigment molecule.

Explanation:

In a light - harvesting complex, when a pigment molecule absorbs a photon, the excited - state electron does not get transferred. Instead, the energy is transferred. The electron in the excited pigment molecule falls back to its ground state, and the energy (not the electron itself) is passed to an electron in a nearby pigment molecule. This is a process of energy transfer (resonance energy transfer) rather than electron transfer in the initial steps within the light - harvesting complex. P680 and P700 are reaction - center chlorophylls, and the transfer to them is a later step in the photosynthetic electron - transport chain, not the immediate fate of the excited - state electron in a light - harvesting complex pigment. Also, it is energy transfer, not multiple electrons being sent directly from excited - state electrons of different pigments in the light - harvesting complex to P680 or P700 at the initial stage.

Answer:

The electron falls back to its ground state, while passing its excited - state energy to an electron in a nearby pigment molecule.