2.1- Photosynthesis 1- Light reaction Flashcards
2 properties of light
particles
waves
particle of light
photon
amount of energy each photon contains
quantum
Relation- E = h × ν
the energy (E) of a photon depends on the frequency of the light
Planck’s law
molecules that absorb light
pigments
transitions to an excited state occur only when the energy exactly matches the energy gap between the ground state energy (Eg) and the excited state energy (Ee)
law of quantum mechanics
4 alternatives in disposing its energy when chlorophyll in unstable during its higher excited state
Fluorescence, relaxation, energy transfer, photochemistry
return to its ground state; release of photon
flourescence
return to its ground state, but no release of photon
relaxation
transfer the energy to another molecule
energy transfer
energy of the excited state causes chemical reactions
photochemistry
light-absorbing pigment all photoautotrophic organisms contain
synthesized by plants, algae, cyanobacteria
chlorophyll
pigment molecular variant of chlorophyll anaerobic photosynthetic bacteria produce
bacteriochlorophyll
C20 long hydrophobic tail in chlorophyll structure
phytol tail
Chlorophyll a absorbs these the most…
violet
orange
Chlorophyll b absorbs these the most…
blue
yellow
tetraterpene (C40) molecules derived from eight isoprene units, the products of the non-mevalonate pathway located in the chloroplast
carotenoids
roles of carotenoids
- responsible for orange/yellow colors
-accessory light-harvesting pigments
-assembly of light-harvesting complexes
-protecting photosynthetic apparatus
site of biophysical and biochemical reactions of photosynthesis
arose from endosymbiotic association of a protoeukaryotic cell + photosynthetic bacterium
chloroplast structure
component of photosystem- absorb light energy, transfer energy to RC
antenna complex
component of photosystem- electron transfer
reaction center
proteins associated w antenna pigments
light-harvesting Complex (LHC) proteins
Electron acceptor type- reduces an Fe-S cluster;
present in green sulfur bacteria
Type 1 (Fe-S type)
Electron acceptor type- reduces quinone; present in purple bacteria
Type II (Q type)
PS II is a light-driven…
water plastoquinone oxidoreductase
PS I is a light-driven…
plastocyanin-ferrodoxin oxidoreductase
major protein complexes in the thylakoid
PS II
Cytochrome b6f
PS I
ATP synthase
Major protein complex in thylakoid- transfer e- from plastoquinol to plastocyanin
Crytochrome b6f
a small water-soluble copper-containing protein
transfer electrons between cytochrome b6f complex and P700
found in lumenal space
Plastocyanin
protein found instead of plastocyanin in certain green algae/cyanobacteria
c-type cytochrome
ATP synthase segment- Transmembrane segment; participates in translocating protons across the membrane to the catalytic portion of the enzyme
CF0
ATP synthase segment- a hydrophilic segment on the stromal surface; involved in the actual conversation of ADP and P to yield ATP, using energy stored in the proton gradient
CF1
400-kDa enzyme that contains 9 different subunits
ATP synthase
CF1 subunit- catalyze the phosphorylation of ADP into ATP
α & β
CF1 subunit- links CF1 to CF0
δ
CF1 subunit- appears to control proton gating through the enzyme
y
CF1 subunit- blocks catalysis in the dark, preventing the breakdown of ATP
may also be involved in proton gating
ε
nucleotide-binding site on enzyme- available to bind ADP and Pi (open)
O-site
nucleotide-binding site on enzyme- in which ADP and Pi are loosely bound (loose)
L-site
nucleotide-binding site on enzyme- where ATP is formed (tight)
T-site
decrease efficiency of photosynthesis from damage caused by toxic photoproducts from high light intensities
photoinhibition
processes dissipate excess absorbed light energy harmlessly as heat
results in de-excitation of the singlet state of chlorophyll in the antenna of PSII
nonphotochemical quenching (NPQ)
