  The most recent crystal structure of the Fenna-Matthews-Olson (FMO) protein
complex indicates that each subunit contains an additional eighth chromophore.
It has been proposed that this extra site functions as a link between the
chlorosome antenna complex and the remaining seven chromophores in FMO [Schmidt
am Busch et al, J. Phys. Chem. Lett., {\bf 2}, 93 (2011)]. Here, we investigate
the implications of this scenario through numerical calculations with the
generalized Bloch-Redfield (GBR) equation and the non-interacting blip
approximation (NIBA). Three key insights into the population dynamics and
energy transfer efficiency in FMO are provided. First, it is shown that the
oscillations that are often observed in the population relaxation of the dimer
composed of sites one and two may be completely suppressed in the eight site
model. The presence of the coherent oscillations is shown to depend upon the
particular initial preparation of the dimer state. Secondly it is demonstrated
that while the presence of the eighth chromophore does not cause a dramatic
change in the energy transfer efficiency, it does however lead to a dominant
energy transfer pathway which can be characterized by an effective three site
system arranged in an equally spaced downhill configuration. Such a
configuration leads to an optimal value of the site energy of the eighth
chromophore which is shown to be near to its suggested value. Finally we
confirm that the energy transfer process in the eight site FMO complex remains
efficient and robust. The optimal values of the bath parameters are computed
and shown to be closer to the experimentally fitted values than those
calculated previously for the seven site system.
