Photosystem

The capture of light for photosynthesis is done by the photosystems, which are structures made of protein complexes and photosynthetic pigments, clustered on the membranes of autotrophic organisms.
In the case of organisms with oxygenic photosynthesis, they have two kinds of photosystems, the photosystem II and Photosystem I which have as a main photosynthetic pigment the molecule of chlorophyll
An important aspect of chlorophyll, is that is relatively easy to promote its electrons of its central ring to upper orbitals, for the absorption of the energy of photons. But is more difficult to remove electrons of the central ring of chlorophyll
If the chlorophyll is placed in the center surrounded by proteins, then the local environment around the chlorophyll is enough charged to remove electrons from the central ring of chlorophyll, to be transferred to other electronic receptor. To this structure is given the name of reaction center
The problem of place a chlorophyll molecule in a core surrounded by proteins, is that the chlorophyll becomes less effective in be excited by light, because a big part of its surface is covered by proteins and cannot capture the photons of light.
The plants have resolved this problem in a very ingenious way, several hundreds of chlorophyll molecules are clustered around the reaction center. Nevertheless none of these molecules of chlorophyll can loss electrons, but they can push their electrons to upper orbitals when absorb the energy of the photons of light.
As these electrons return to ground state, the energy released is enough to excite the electrons in adjacent chlorophyll to higher orbitals.
Therefore the energy obtained from the initial photons, jumps between chlorophylls until by chance it jumps to the central chlorophyll. Here the energy is sufficient to push electrons out of the central chlorophyll of the reaction center
In this way the energy obtained from the initial jumps of the photons between chlorophylls resonate until the photons have the opportunity of jump to the central chlorophyll, thus the accumulated energy is enough to push the electrons out of the central chlorophyll.
The chlorophylls that are not inside of the reaction center collect the light in the same way of an antenna and canalize the energy towards the central chlorophyll which is oxidized for the loss of an electron.
Thus the electron hole made will be filled for an electron coming from the breaking of the water molecules done during photosintesis
Finally it is necessary to say that the antenna system is even more clever because other pigments such as carotenes, phycoerythrins and phicocyanines, also form part of this antenna system which means that plants can capture almost all the spectrum of visible light.