Summary Absorption Spectra, Photosynthetic Pigments and Photosystems

Absorption Spectra, Photosynthetic Pigments & Photosystems:
Absorption Spectra:
 The percentage of light each pigment absorbs at different
wavelengths can be plotted on an absorption spectrum.
 The photosynthetic pigments absorb most light at the blue &
red ends of the spectra & absorb little/ no green light.
 This is because green light is the most abundant so would cause
damage to the organism.
 This fact was tested through an experiment using mobile
oxygen seeking bacteria in a tube with green algae
(photosynthesising organism).
 Light was shone on the algae through a prism that separated
the different wavelengths of light.
 Most bacteria congregated around the blue and red light.
 This suggested that the most oxygen was being produced at the
blue & red ends of the spectra.
 Which shows that the algae was using red & blue light the most
in photosynthesis.


Photosynthetic Pigments:
 Chlorophylls:
o A collection of green pigments.
o They all have a hydrocarbon tail & porphyrin head.
o Their tails embed themselves in the membranes of the
thylakoids.
o The head remains on the membranes surface.
o Chlorophyll a is found in all plants.
o There are two types of chlorophyll a: P680 & P700.



 Carotenoids: