קומפלקס האנטנה

The reaction center of a photosystem itself is not efficient enough to meet the energy demand of the electron transport chain.

Therefore, it is surrounded by a light harvesting complex or LHC that comprises several hundred pigment molecules, including chlorophyll a, chlorophyll b, and other accessory pigments.

Unlike the reaction center, LHC pigments cannot directly convert light energy into chemical energy and are therefore photochemically inactive.

However, these pigments function as an antenna by absorbing photons of varying wavelengths and rapidly transferring energy to the reaction center.

The energy transfer from one pigment to another depends on the distance between the molecules.

Therefore, antenna pigments are positioned close to each other by a protein scaffold, forming an energy-efficient complex.

Within the antenna complex, the absorbed energy can only be transferred from a pigment molecule that absorbs light of a shorter wavelength to another that absorbs a longer wavelength.

Thus, the energy is funneled through a network of pigment molecules starting from the periphery to the ones located closer to the reaction center.

Finally, the energy is transferred to the reaction center, where the special-pair of chlorophyll molecules absorbs photons of the longest wavelengths.

The reaction center can now transmit an adequate number of electrons to the electron transport chain, enhancing its yield.