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Plant Phys Exam 2
Terms in this set (53)
Study of mechanisms that allow organisms to
respond to their environment
of light energy to convert ADP to ATP
the chemical reactions that convert CO2 and other compound into glucose using byproducts of light reactions (ATP & NADPH)
depicts the magnitude of a response of a
biological system to light as a function of
Fluorescence resonance energy transfer (FRET)
physical mechanism by which excitation energy is conveyed from chlorophyll to reaction center
Which pigment is found in all plants?
Which processes results in the
loss of electrons?
The antenna complex collects light energy &
transfers it to the ___________ complex.
Chlorophyll uses what 4 pathways to dispose of
Fluorescence, heat, energy transfer, Photochemistry
What are the 3 thylakoid reactions?
Electrons extracted as H2O oxidized to O2 2H2O → O2 + 4 [H.]; reduce NADP+ to NADPH; ATP is formed
Absorb shorter wavelengths of light (<680 nm)
Associated with photolysis of H2O
Main function is ATP synthesis and reduction of
NADP+ to NADPH-
Photoreceptor is P680
Located on the outer surface of thylakoid
During the Calvin
Benson cycle triose
phosphates are converted to starch in
chloroplasts and exported to cytosol as
increase in the rate of CO
fixation with time
during the first few minutes after onset of
Benson Cycle takes place in what
part of the chloroplast?
acceptor in Calvin
List and describe the three phases of the Calvin
Carboxylation (carbon fixation): light-independent reactions are initiated; CO2 is fixed from an inorganic to an organic molecule; CO2 covalently linked to carbon skeleton; b. Reduction (reduction reactions): ATP and NADPH are used to reduce 3-PGA into G3P; then ATP and NADH are converted to ADP and NADP+; c. Regeneration (ribulose 1,5-bisphosphate (RuBP)): RuBP is regenerated
Light has properties of both a _____ and a
What is a photon?
Tiny packets of light or radiant energy
functional responses of plants to changing
Photoacclimation via pigment production; changes in photosynthetic rates, reorientation of chloroplasts, phototactic and phototrophic response, Initiation of chloroplasts
What are 3
mechanisms plants use to reduce
Radiative heat loss; sensible heat loss, latent heat loss
How do carotenoids provide
photosynthetic reaction centers?
Carotenoids photoprotection: Vent excess by excitation transfer to carotenoid before damage occurs
the difference in charge and chemical
concentration across a membrane
chlorophyll in which the central magnesium ion
has been replaced by 2 hydrogen ions
complex set of molecular processes resulting in
the inhibition of photosynthesis by excess light
the diurnal motion or seasonal motion of plant
parts (flowers or leaves) in response to the
direction of the sun
Process by which ions exit the
symplast of a xylem parenchyma cell & enter the conducting cells of the xylem for translocation
Hydrogen ions are brought through the thylakoid
membrane from the
to the lumen by
cytochrome b6f complex
Protons are transferred from the thylakoid
lumen to the
How does electron transfer differ between
pigments and within reaction centers?
Pigments - purely physical process; Reaction centers - redox reactions
What is the name of the cycle by which the
Cytochrome b6f complex pumps H+ ions into the lumen?
What part of the light reaction process results in
ATP production but no NADPH production while
also generating a change in pH without
accumulation of reduced species?
Cyclic electron flow
What is the difference between steady state and
Steady state: stable over time, requires continual work; Equilibrium: stable over tie, no energy or work required
Solute transport occurs across what 3 levels?
individual cells, short distance transport (cell to cell), long distance transport (whole plant)
By initially following and then
deviating from the predicted uptake rate, this figure
illustrates what about the kinetics
of the sucrose uptake mechanism?
Indicates more than one mechanism ~ both low & high affinity transporters
How do active and passive transport differ?
Passive transport: Movement down a gradient of free energy (chemical potential) until reaching equilibrium; b. Active transport: Movement of substances against a gradient of chemical potential; Requires application of cellular energy (e.g. hydrolysis of ATP)
What are the 3 main types of membrane
Channel, carrier, protein pumps
C3 or CAM during day
Pathway of CO
fixation is C
Involves both mesophyll and bundle sheath cells
First stable product of CO
acceptor varies temporally
Why are carrots orange?
Carrots color due to carotenoid β-carotene
What are two ways that photorespiration is
wasteful compared to C
3Phosphoglycerate is created at a reduced rate and higher metabolic cost ; b. Results in a net loss of carbon ~ 25% of carbon fixed by photosynthesis is re-released as CO2; Loss of N ~ ammonia must be detoxified at a substantial cost to the cell; d. Direct cost of one ATP and one NADPH
oxidative photosynthetic carbon cycle is also
Give 3 examples of environmental conditions
which increase photorespiration.
CO2 is lower or O2 is higher, Temps are high, too much light
Why does energy from photons follow a
directional pathway down pigment antennas
they are captured by the chloroplast
Red shift means energy of excited state is lower near rx center than outer edge of antenna system; b. Difference in excitation energy between transfers lost as heat - do not have as much energy longer wavelengths cannot be picked up by pigments that only collect light at shorter wavelengths
Explain how quantum efficiency of plants can be
high while energy efficiency and solar mean
storage efficiency are low.
a. Quantum efficiency (quantum yield) = measure of the fraction of absorbed photons that engage in photochemistry
b. Energy efficiency = measure of how much energy in the absorbed photons is stored as chemical products
c. Solar energy storage efficiency = measure of how much of the energy of the entire solar spectrum is converted to a usable form
blurry pic, sorry
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