Photosynthesis: Light Reaction Flashcards
walang kamatayang photosynthesis
Photosynthetic organisms use this energy to synthesize complex carbon compounds.
solar energy
Light may appear as both __ and __.
particle; wave
The distance between successive wave crests is called ___.
wavelength
The number of wave crests that pass an observer in a given time is called ____.
frequency
The light wave is a ___ electromagnetic wave.
transverse
Light as a particle is called a __.
photon
Energy in a photon
quantum
The energy (E) of a photon depends on the frequency of the light. True or False?
True; known as Planck’s Law
Explain the relationship between (1) energy and frequency, and (2) energy and wavelength.
e = hv
e = hc/λ
Molecules that absorb light
pigments
Colors that chlorophyll absorb and reflect
blue and red: absorbed
green and yellow: reflected
Transitions to an excited state occur only when the energy exactly matches the energy gap between the ground state energy and the excited state energy.
law of quantum mechanics
When excited, chlorophyll may return to its ground state and release photon. This is called ___.
fluorescence
When excited, chlorophyll may return to its ground state, but no release of photon, which is known as ___.
relaxation
Chlorophyll may also transfer the energy to another molecule when excited. This is called ___.
energy transfer
The energy of the chlorophyll’s excited state causes chemical reactions. This is known as ___.
photochemistry
All pigments are found in the chloroplast. True or False?
true
Plants, algae, and cyanobacteria : chlorophyll
as
anaerobic photosynthetic bacteria :
bacteriochlorophyll
Number of rings found in a chlorophyll that are similar with the heme and cytochrome; known as ____.
four; porphyrin rings
Element that is central to the porphyrin ring.
magnesium; fe in heme
Long hydrophobic tail in a chlorophyll with 20 hydrocarbons.
phytol tail
Chlorophyll a & b : ____
Chlorophyll c, d, & f : ____
green plants
protists and cyanobacteria
Chlorophyll a absorbs _____.
Chlorophyll b absorbs _____.
violet and orange
blue and yellow
Tetraterpene (C40) molecules derived from eight isoprene units responsible for coloration, assembly of light-harvesting complexes, and protection of photosynthetic apparatus from photooxidative damage; accessory light‐harvesting pigments.
carotenoids
Site of biophysical and biochemical
reactions of photosynthesis.
chloroplast
Third membrane system of chloroplast
thylakoid membrane
Two complexes in pigments
antenna pigments; reaction center complex
Photosystems are made up of ___.
LHC Proteins + pigments
Photosystems are embedded in the ____.
thylakoid membrane
energy transfer: ____
electron transfer: ____
antenna pigments
reaction center
Proteins associated with antenna pigments which are structurally related.
light-harvesting complex
PS II is associated with ___; PS I is with ___.
LHC II; LHC I
Two types of reaction center on the nature of electron acceptor
type I, type II
An RC based on electron acceptor that reduces a Fe-S cluster and is present in green sulfur bacteria.
type I
An RC based on electron acceptor that reduces quinone and is present in purple bacteria.
type II
Dimeric multi-subunit protein super complex.
PS II
A large multi-subunit complex which is approximately made up of 15 proteins.
PS I
RC in PS I
P700
RC in PS II
P680
PS II is a light-driven ___.
water-plastoquinone oxidoreductase
PS I is a light-driven ____.
plastocyanin-ferredoxin oxidoreductase
What are the four major protein complexes in the thylakoid?
- PS II
- cytochrome b6f
- PS I
- ATP synthase
PS II is located in the ____.
granal thylakoid
Cytochrome b6f is evenly distributed in the thylakoid. True or False?
true
PS I & ATP synthase are in the ____.
stromal thylakoid
Dimers that transfer electrons from plastoquinol to plastocyanin.
cytochrome b6f
Small, water-soluble, and copper-containing protein that transfers electrons between the cytochrome b6f complex and P700.
plastocyanin
Plastocyanin is found in the ____.
lumenal space
In certain green algae and cyanobacteria, a c-type cytochrome is sometimes found instead of plastocyanin.
true
ATP Synthase has two segments: ___ and ___.
CF0 and CF1
Transmembrane segment; participates in translocating protons across the membrane to the catalytic portion of the enzyme.
CF0
Hydrophilic segment on the stromal
surface; involved in the actual conversion of ADP and Pi to yield ATP, using energy stored in the proton gradient.
CF1
Chloroplast ATP synthase is a 400‐kDa enzyme that contains __ different subunits.
nine
Proton translocation + Phosphorylation of ATP
chemiosmosis
What are the three nucleotide‐binding sites on the enzyme?
- o-site
- l-site
- t-site
Nucleotide-binding site that is available to bind ADP and Pi; open.
o-site
Nucleotide-binding site wherein ADP and Pi are loosely bound; loose.
l-site
Nucleotide-binding site where
ATP is formed; tight.
t-site
The movement of H+ across the membrane drives rotation of the γ subunit in the enzyme, causing conformation changes that interconvert the 3 sites.
true
Decreased efficiency for photosynthesis due to high intensities of light
photoinhibition
Processes that dissipate excess absorbed light energy harmlessly as heat resulting in de‐excitation of the singlet state of chlorophyll in the antenna of PSII.
nonphotochemical quenching (npc)
Carotenoids that have been implicated in NPQ
xanthophylls and lutein
QB⁻
semiquinone
QBH₂
plastoquinol
A₁
phylloquinone
Types of chloroplast electron transfers and subsequent phosphorylation:
▪ Non-cyclic/linear electron transfer = linear photophosphorylation
▪ Cyclic electron transfer = cyclic photophosphorylation
true
Products of Light Reaction
ATP and NADPH
