Chlorophyll and other photosynthetic pigments; chlorophyll contains
porphin ring with magnesium at the centre linked to a long
hydrocarbon chain. Chlorophyll is the most important pigment in plants
because it is the the only one that takes a direct part in photosythesis.
As well as chlorophyll, there are other photosynthetic
pigments in chloroplasts called accessory pigments.
These do not participate directly in the light-dependant
reactions, but they absorb light of other wavelengths
outside the range of chlorophyll and convey the energy
to chlorophyll which then uses it in photosynthesis
Absorption spectrum and action
spectrum; the absorption
spectrum refers to the
wavelengths of light that a
particular photosynthetic pigment
absorbs. The action spectrum
refers to the wavelengths of light
that bring about photosynthesis
The production of ATP and reduced NADP; the light-dependant reaxtions
occurs in chlorophyll bound to the thylakoid membranes in a chloroplast.
Light absprbed by chlorophyll provides energy to convert ADP and
inorganic phosphate to ATP, a process called photophophorylation
When a chlorophyll absorbs light, the energy level of its electrons is raised; the electron goes from its ground
state to an excited state. Electrons in their excited state leave the chlorophyll molecule are passed a chain of
electron carrier molecules called an electron transport chain. A redox reaction takes place during the transfer of
an electron from one carrier molecule to the next. One carrier molecule donates an electron while the other
molecule accepts it. NADP is the final electron acceptor in the electron transport chain
As electrons pass down the
elctron transport chain in the
series of the redox reaction,
they release energy whichi is
used to make ATP. This
method of ATP production is
called photopsophorylation
because light energy is used to
add a phosphate group to ADP
Photolysis; is where the light energy trapped by chlorophyll is also
used to split water molecules and release electrons. Photolysis occurs
when water molecules are split with the aid of light energy