Chapter 13 Flashcards
________ moves protons from Photosystem II to photosystem I. Note Photosystem I is at a high energy state than photosystem II
proton motive force
moelcular structures and complexes that are receptive to light? These are the things that absorb light and they go to a excited state and they emit a color and go back to a ground state? ( this is the color you see
chromophore
what has pigment molecules that absorbs light?
photoreceptor molecules
resonance energy transfer
excitation energy is transferred to a neighboring molecule via resonance
Electron transfer result in ____________–
photoinduced charge separation
_______________ is the primary light acceptor in most photosynthetic systems
chlorophyll
chlorophyll is part of the special pair in the reaction center that undergoes charge separation
chlorophyll is a heterocyclic ring derived from ______________ with a ________ in the middle
pyrrole
Mg
Which has a higher oxidation state? chlorophylls alpha or beta
chlorophyll beta has a higher excitation state
Antenae pigments are:
light-harvesting complexes that enhance the efficiency of photons.
Forex. chlorophyll alpha, chlorophyll beta, lutein, beta carotene
antenna chlorophylls, carotenoids and other accessory pigments aborb light as energy and transfer it between molecules to the _______________
reaction center
The reaction center is where photochemical reaction occurs to convert the energy of a photon into a separation of charge, initiating electrong flow
what are the two photosystems that generate a proton gradient and NADPH? give brief description of roles
PS II- replenishes electrongs, proton gradient for ATP synthesis
PSI- generates reducing power
Photosystem II (680) is composed of what dimers
This special pair is called D1 and D2
Photosystem II and oxygen generation?
When energy is transferred to P680 in PSII, the newly energized electron is ejected and donated to pheophytin
The oxygen-evolving complex is responsible for transfer of electrons from water to oxidized P680
P680* is a strong oxidant that extracts electrons from water to maintain redox balance while generating O2.
This reaction, the photolysis of water, occurs at the manganese complex of photosystem II.
The photolysis of water is the source of O2 for all of life.
the __________________ is the source of all O2 for all life
photolysis of water
photosystem I uses light energy to generate reduced ferredoxin, a power reductant
- Reaction center
- electron transport chain
- biosynthetic reducing power
Photosystem I and NADPH Synthesis
Absorption of a photon by P700 leads to the release of an electron that is passed through a series of electron carriers
The first electron carrier is chlorophyll a and the last is ferredoxin
____________ transports electrons from PS1 to reductase
ferredoxin
- Ferredoxin donates its electron to ferredoxin-NADP oxidoreductase
- to produce NADPH, two electrons are needed; this is the ____________ pathway
noncyclic electron transport pathway
-The abosorptions of eight photons yields an ATP/ NADPH ratio 3:2
2 Hydrogens enter from the __________ and 4 hydrogens are emitted into the ____________ to make a proton gradient
stroma
thylakoid lumen
Photosystem I produces a powerful
reductant, whereas photosystem II produces a powerful
oxidant. Identify the reductant and oxidant and describe
their roles.
Photosystem I generates ferredoxin, which reduces NADP1 to NADPH, a biosynthetic reducing power.
Photosystem II activates
the manganese complex, an oxidant capable of oxidizing water, generating electrons for photosynthesis, and generating protons to form a proton gradient and to reduce NADP1 and O2.
____________ drives ATP synthesis
proton gradient
cyclic electron flow, what does it make? and what it not make?
no NADPH or O2 is generated, it make ATP instead
More NADH is made if there are multiple folds (there is more photosystem II and cytochrome bf), while equal amounts of ATP can be made just outside the membrane
General (went with a photo)
in non cyclic _______ photons are required to yield two molecules of NADPH and ___________ molecules of ATP
eight photons
three ATP
in cyclic photophosphorylation, _____ photons yield ____ ATP but no NADPH
two photons
one ATP
the calvin cycle traps CO2 gas as ______________, a precursor to hexose sugars
phosphorglycerate
What are the three stages of the Calvin Cycle?
- Fixation of CO2 by ribulose 1,5-bisphosphate to form two molecules of 3-phosphoglycerate
- The reduction of 3-phosphoglycerate to hexose sugars
- The regeneration of ribulose 1,5-bisphosphate
The fixation of CO2, the rate LIMITING STEP in hexose synthesis, is catalyzed by ____________
rubisco
Ribulose Can work with what enzymes?
phosphopentose isomerase
phosphopentose epimerase
phosphoribulose kinase
___________ molecules of ATP and ___________ molecules of NADPH are required for the incorporation of each molecule of CO2 into hexosse
three molecules of ATP
two molecules of NADPH
what are the two fates of the fix carbons from photsynthesis?
Starch, which is synthesized and stored in the chloroplast.
- Sucrose, which is synthesized in the cytoplasm from 3-phosphoglycerate. Sucrose is the transport form of carbohydrates in many plants.
the synthesis of sucrose uses what enzyme
sucrose 6 phosphate synthase
why is the calvin cycle crucial to the functioning of all life forms?
The Calvin cycle is the primary means by which gaseous CO₂ is converted into organic matter (biomolecules)
All carbon atoms in your body have passed thru rubisco and the Calvin cycle at some point
Rubisco increases with?
light exposure
alkaline pH/Mg+2
_______________ plays a key role in regulating the calvin cycle
thioredoxin
Photosystem I generates reduced ferredoxin and NADPH, both of which regulate enzymes of the Calvin cycle.
Ferredoxin-thioredoxin reductase activates key enzymes by reducing _____________.
disulfide bonds
Enzyme activation/deactivation by thioredoxin
reduced ______ alters activity of several Calvin cycle enzymes-both positively and negatively
thioredoxin
what affects photosynthesis?
PH, MG+2, ferredoxin-thioredoxin system, phytochrome
plants that produce glycerate-3-phosphate as the first stable product of photsynthesis are called ____________–
C3 plants
Photorespiration – instead of fixing carbon, fixes oxygen
In hot _______, Rubisco’s affinity for O2 increases
Plants need to conserve water, so plants close stomata, so CO2 cannot diffuse in…and O2 can’t diffuse out…O2:CO2 increases
conditions
C4 metabolism—
Sugar cane and maize (corn) can thrive under drought and high-temperature conditions
Crassulacean Acid Metabolism (CAM)
Mechanism to conserve water (dessert plants)
Open stomata only at night
photorespiration
Light-dependent process where oxygen is consumed and CO2 is produced
Multistep process initiated by RIBULOSE BISPHOSPHATE CARBOXYLASE
rubico can react with O2 instead of CO2 to generate ____________ and __________-
phophoglycerate and phosphoglycolate
Because O2 is consumed and CO2 is generated, the process is called ______________
photorespiration
why does photorespiration occur?
occurs when the CO2 levels inside a leaf become low. This happens on hot dry days when a plant is forced to close its stomata to prevent excess water loss.
what enzyme is used in C4 metabolism?
phosphoenolpyruvate (it has a higher affinty for Co2)
Oxaloacetate is reduced to malate, which then diffuses into the bundle sheath cells
What are athe best regulators of photsynthesis?
- Ph-During light reaction, protons are pumped out of the stroma, increasing pH
- Mg2+—Light increases the stromal concentration of Mg2+, which is required for activity of some enzymes
- The ferrodoxin-thioredoxin system—Thioredoxin (small protein) transfers electrons from ferredoxin to several enzymes
Alters the activity of these enzymes (e.g., NADP+-glyceraldehyde-3-phosphate dehydrogenase among others) - Phytochrome—120-kD protein that possesses a red-light sensitive chromophore
Activation triggers several transduction pathways, activating hundreds of plant responses to light (e.g. seed germination)
water serves as a source of ____________ when electrons are transferred from photosystem II to photosytem I to NADP+. When H2O gives up its electrons, the oxygen in H2O is oxidized to O2
source of electrons
the __________ shows where electrons go during photosynthesis
z scheme
what is the path of electrons through the photosytem in the presence of light?
H20 –> PSII –>plastoquinone –>cytochrome bf complex –> plastocyanin –> photosystem I –>ferredoxin –> ferredoxin-NADP oxidoreductase –>NADP
what is the function of photosystem II?
is to oxidize water molecules and donate energized electrons to electron carriers which eventually reduce photosystem I
Give locations of the following:
PQ
cyt bf
PC
FNR
PQ in membrane
cyt bf in membrane
PC in lumen
FNR in stroma
______electron transport pathway involves Ferredoxin–>FNR.
noncyclic
FNR uses two electrons to reduce NADP to NADPH
in _________ electron transport pathwayFerredoxin–>PQ
cyclic
an extra H is made to make an additional ATP
_________________ is the light-driven synthesis of ATP from ADP + P
photophosphorylation
what are the phases of the calvin cycle?
- carbon fixation- uses rubisco, requires ATP
- reduction of glycerate 3- phosphate- by NADPH to form glyceraldehyde-3-phosphate
- regeneration of ribulose-1-5- bisphosphate= of every six glyceraldehyde-2-phosphates formed, five are regenerated to form three molecules of ribulose-1,5,-bisphosphate
Photosynthesis depends on _________,____________, and _________-
temperature, cellular CO2 concentration, and light
light affects enzymes (rubisco) by indirect mechanism? which and desribe
- PH
- MG+2
- Ferredoxin-thioredoxin system
- phytochrome
compare mesophyll cells and bundle sheath cells
mesophyll cells
- in direct contact with air
- lack rubisco
- light reactions make ATP, NADPH
bundle sheath cells
- in contact with vascular tissue
- have rubisco
- calvin cycle reactions use CO2 released
