Accessory pigments are
light-absorbing compounds, found in
photosynthetic organisms, that work in conjunction with
chlorophyll a. They include other forms of this pigment, such as chlorophyll
b in
green algal and
higher plant antennae, while other algae may contain chlorophyll
c or
d. In addition, there are many non-chlorophyll accessory pigments, such as
carotenoids or
phycobiliproteins, which also absorb light and transfer that light
energy to
photosystem chlorophyll. Some of these accessory pigments, in particular the carotenoids, also serve to absorb and dissipate excess light energy, or work as
antioxidants. The large, physically associated group of chlorophylls and other accessory pigments is sometimes referred to as a
pigment bed, though this term is no longer supported by what we know of photosystem and antenna complex structures.