electromagnetic energy › solar energy or radiation which travels in space a rhythmic waves and can...
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Photosynthesis Part 2Pages 112 to 113
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Solar Energy to Chemical Energy – Vocab Review
Electromagnetic energy› Solar energy or radiation which travels in
space a rhythmic waves and can be measured in photons
Wavelength› The distance between crests of adjacent
waves such as those of the electromagnetic spectrum
Visible Light› The radiation our eyes see as different colors
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UV
Fig. 10-6
Visible light
InfraredMicro-waves
RadiowavesX-raysGamma
rays
103 m1 m
(109 nm)106 nm103 nm1 nm10–3 nm10–5 nm
380 450 500 550 600 650 700 750 nm
Longer wavelengthLower energyHigher energy
Shorter wavelength
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Vocab continued…
Pigments › Substances that absorb some wavelengths
of light and reflect others› Different pigments absorb/reflect different
wavelengths Photon
› A fixed quantity of light energy› The shorter the wavelength of light the
greater the energy of a photon
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Fig. 10-7
Reflectedlight
Absorbedlight
Light
Chloroplast
Transmittedlight
Granum
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Chlorophyll – primary pigment of photosynthesis
Which wavelengths are absorbed most?› Primarily blue and red
Why do plants appear green?› They reflect green light
What is the role of accessory pigments?› They allow the plant to absorb energy from
more the visible light spectrum – making the plant more efficient.
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Fig. 10-9
Wavelength of light (nm)
(b) Action spectrum
(a) Absorption spectra
(c) Engelmann’s experiment
Aerobic bacteria
RESULTS
Rate
of
ph
oto
syn
thesis
(measu
red
by O
2 r
ele
ase)
Ab
sorp
tion
of
lig
ht
by
ch
loro
pla
st
pig
men
ts
Filamentof alga
Chloro- phyll a Chlorophyll b
Carotenoids
500400 600 700
700600500400
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Excitation of chlorophyll by light
When a pigment absorbs light, it goes from a ground state to an excited state, which is unstable
When excited electrons fall back to the ground state, photons are given off, an afterglow called fluorescence
If illuminated, an isolated solution of chlorophyll will fluoresce, giving off light and heat
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Photosystems capture solar power
Photosystem (1st part)› Light harvesting
complexes pigment molecules
bounded by proteins; absorb
transfer energy to chlorophyll a of reaction center
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Photosystems capture solar power
Photosystem (2nd part)› Reaction Center
Chlorophyll a and a primary electron acceptor
Chlorophyll a uses energy from light harvesting complexes to pass a pair of electrons to the primary electron acceptor