Photosynthesis 1 Flashcards
Pigment
any substance that absorbs light
energy
The color that something is, is what it reflects
Chloroplast pigments:
Chlorophyll
Carotenoids
Chlorophyll
green (reflect green)
* Absorb in red, violet, and blue regions of spectrum
Carotenoids
red, orange, yellow
A)carotenes: red, orange, yellow
B)xanthophylls: pale yellow
Action Spectrum for Photosynthesis
-Shows the relative effectiveness of different
wavelengths of light in promoting photosynthesis
Absorption Spectrum of a pigment shows
the
wavelengths of light that are absorbed by a
pigment.
If one compares the Action Spectrum of a
process with Absorption Spectra, one can get
an idea of
what pigments play a role in the
process.
When one compares
the action spectrum for
photosynthesis with the
absorption spectra for
chlorophylls a and b and
for carotenoids
they
overlap supporting that
chlorophylls and
carotenoids absorb light
for photosynthesis.
When isolated chlorophyll (no longer in chloroplasts) absorbs
light,
the energy levels of electrons are elevated.
– These electrons are said to be in an excited state.
– The excited electrons drop back to the ground state, and
energy is released as fluorescence; and some
energy is lost as heat
light=
fluorescence
When chlorophyll absorbs light energy while in chloroplast
membranes or other photosynthetic membranes:
– The excited electrons do not drop back down to the
ground state, but are transferred to electron carriers.
– The energy is trapped and stored in chemical bonds
Adenosine triphosphate (ATP) =
Energy
currency of cell.
Plants make ATP using
light as an energy
source.
Photosynthesis Takes place in
membranes of chloroplasts or
in membranes of photosynthetic prokaryotic
organisms
where does the Light-Dependent Reactions happen in
thylakoid membranes of chloroplasts
step 1 of Light-Dependent Reactions
Water molecules split apart, releasing electrons and
hydrogen ions; oxygen gas released.
step 2 of light dependent reactions
Electrons pass to electron carriers of electron
transport system.
step 3 of light dependent reactions
NADP (nicotinamide adenine dinucleotide
phosphate) is reduced, forming NADPH (reduced
nicotinamide adenine dinucleotide phosphate)
– used in light-independent reactions
Hydrogen ions play major role in
ATP production
Light-Independent Reactions happens where specifically in the chloroplast
In stroma of chloroplasts