Lectures 8-9-10-11 Flashcards
which cells are the most active photosynthetic cells? Where is the primary site of photosynthesis
mesophyll cells
mesophyll cells contain [blank] which contain [blank]
chloroplasts, chlorophylls
Photosynthesis occurs in two stages (2 reactions)
Thylakoid reactions and carbon fixations reactions
What happens in the thylakoid reactions
ocurs in the internal membrane of chloroplasts,
production of thylakoid reactions
ATP and NADPH
thylakoid reactions are light [blank]
dependent
calvin reactions/carbon fixation are dark reactions and are light [blank]
independent
carbon fixation reactions occur where and produce what
stroma, produce sugars
formula for reaction
6co2 + 6h20 —> c6h12o6 + 6o2
water is [blank] to release [blank], co2 is [blank] to form [blank]
oxidized to release oxygen, reduced to form sugars
Wavelength
distance between wave crests
frequency
frequency (v)
number of crests passing
Energy (E)
depends on frequency
explain E=Hv
Energy is equal to Planck’s constant x frequency
light behaves as a wave and as a photon
explain c = lambda v
c is the speed of the wave = wavelength x frequency
visible spectrum of light absorption of chlorophyll is from
400 to 700
when chlorophyll absorbs a photon, what happens
it transitions to a higher excited state (higher when absorbing blue light than red)
excited energy can be dissipated in 4 ways
-Fluorescence (re-emitting as light),
-Heat loss,
-Energy transfer to other molecules,
-Photochemistry to drive reactions.
chlorophyll a and b absorb what light and reflect what light
red and blue light, reflect green, so theyre found in green plants
chlorphyll c and d are found in what type of organisms
protists/ cynaobacteria
structure of chlorophyll
prophyrin ring and hydrocarbon tail
accesory pigments like carotenoids absorb what color, at what wavelength
orange to yellow, at 400 to 500 nm
structure of carotenoids molceularly
linear with many double bonds
carotenoids transfer absorbed light energy to
chlorophyll
some light energy absorbed by chl is stored as
chemical bonds
[blank] serves as antenna complexes
pigments
Antennae complexes absorb light and transfer energy to [blank] centers, where it’s used for [blank] reactions to [blank]
reaction, redox, store long term energy
Each reaction center is associated with an [blank]
antenna complex
Quantum yield (Φ) is defined as the number of
photochemical products divided by the number of quanta absorbed.
explain a 0, 1, and 0.95 quantum yield
0 = process does not respond to light
1 = every absorbed photon contributes
0.95 = dim light, fluorescence at 0.95
how is atp and nadph in light reactions form
redox reaction - electrons are transferred to nadp+ which reduces it to nadph
nadph and atp are made from [blank] reactions and use to drive [blank]
light, carbon fixation
action spectrum shows what
the response of a biological system to light as a function of wavelength
in the light reactions, for every 2 molecules of water split, how many nadp+ and nadph are release
2 nadp+ reduced to make 2 nadph, every 2 molecules of water releases one O2
many compounds serve as an artificial electron acceptor in the [blank] reaction
Hill
PSII functions best with which wavelength? Does it work well with far-red? What does it produce
best with red light, 680 nm, produces strong oxidants (WEAK REDUCTANT) to split water and release O2
PSI prefers red or far-red? What wavelength? What does it produce?
Functions with far-red light (~700 nm or greater than 680), producing strong reductants (weak oxidants) (NADPH), can reduce NADP+
explain red drop effect
sudden decrease in photosynthetic efficiency when plants are exposed to light with a wavelength longer than 680 nm (in the far-red region).
Why does this happen?
Photosystem II (PSII) operates most efficiently at a wavelength of around 680 nm, which is why it’s called P680. If the light provided to the plant is only longer than 680 nm (like far-red light), it primarily excites Photosystem I (PSI, which absorbs best at 700 nm, hence called P700).
When only PSI is activated, the electron transport chain doesn’t operate efficiently, and ATP and NADPH production declines, leading to a drop in the rate of photosynthesis.
explain the emerson enhancement effect
Emerson observed that when plants are exposed to both red light (around 680 nm) and far-red light (greater than 680 nm) simultaneously, the photosynthetic rate increases significantly compared to using either wavelength alone, optimizing the flow of electrons through the electron transport chain and enhancing the production of ATP and NADPH
The [blank] is a model that describes the flow of electrons through the two photosystems, Photosystem II (PSII) and Photosystem I (PSI), during the light-dependent reactions of photosynthesis.
Z scheme
The Z-scheme captures the movement of electrons from [blank] to [blank], forming NADPH through a series of redox reactions.
water to napd+
The two photosystems are responsible for [blank] and driving the [blank] to create ATP and NADPH, which are then used in the Calvin Cycle.
capturing light energy, electron transfer
Which equation is this for:
2H2O→4H+ +4e− +O2
photolysis of water in PSII
- releases electrons (4) that replace the ones that were lost in 680
- releases oxygen
- release protons for gradient
Electrons from P680 (PSII) are transferred to [blank], which then transports them to the [blank].
As the electrons move through the cytochrome complex, they drive the pumping of [blank] into the [blank]. This builds up a proton gradient that will later be used to produce ATP.
plastoquinone (PQ), cytochrome b6f complex, protons, thylakoid
what does PSI do, in terms of pc or pq, etc
PSI absorbs photons, exciting electrons in the P700 chlorophyll molecule to an even higher energy state.
Electron Replacement: The electrons lost from P700 are replaced by the electrons coming from PSII 680.
Electrons carried via plastocyanin (PC).
The excited electrons from P700 are passed down to a protein called ferrodoxin (Fd).
From there, the electrons are transferred to NADP⁺ reductase, which reduces NADP⁺ to NADPH.
how is atp made from psI and psII
The movement of electrons from PSII to PSI results in a proton gradient (H⁺) across the thylakoid membrane.
This gradient is used by the enzyme ATP synthase to convert ADP into ATP via chemiosmosis.
PSI transfers proteins into [blank] lamellae
grana
PSII tranfers proteins into [blank] lamellae
stroma
plastocyanin (PC) is blue-colored copper, and is used in which photosytstem
PSI
Plastoquinone is used in which photosystem
PSII
PSII is easily damaged by
excess light
