bich 2 exam 3 Flashcards
Draw the malate-aspartate shuttle
On doc
Draw the glycerophosphate shuttle
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Name the electron transport proteins in order
Glycerophosphate Dehydrogenase (part of glycerophosphate shuttle) Complex I, Complex III, Complex II, Complex IV
Draw the electron transport chain with the flow of electrons and proton
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Draw the Q cycle
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Why does the q cycle run twice for UQH2?
In the first half-cycle, a ubiquinol molecule attaches onto complex III and transfers the two electrons to the cmplex.
In the second half-cycle of the Q cycle, another ubiquinol attaches onto complex III. Upon binding, the two protons are moved into the intermembrane space and the two electrons follow the same pathways as before.
Describe the Mitchell chemiosmotic theory
Proposed that energy derived from electron transport is stored as an electrochemical potential (pH and
Electrical gradient), which is used as energy to synthesize ATP from ADP and Pi.
How did Racker and Stoekenius confirm Mitchell’s hypothesis?
Reconstitution experiment: generated lipid vesicles containing
bacteriorhodopsin (a light-driven proton pump) and bovine
mitochondrial F0F1 ATP synthase
How does the F1-F0 ATP Synthase work?
Protons enter through the A subunit and bind a c-subunit. This rotates the c ring. One proton binds to each subunit, pushing it to rotate in a complete circle
Protons then exit through the A subunit back into the matrix
The stalk rotates with the c=ring and the stalk hits the alpha/beta subunits causing these subunits to change conformation
Draw a model of the F0F1 ATP synthase and how does it work?
on doc
How do uncouplers affect the proton gradient and ATP production?
Uncoupler: protein or chemical that dissipates the proton gradient as heat
How the light harvest complex (LHC) works and how energy is absorbed and passed?
Photon strikes a pigment molecule in the LHC, excites an electron to a higher energy level. Pigments arranged so they have different absorption spectrum and can capture different wavelengths.
Once excited: the energy from the absorbed photon is quickly transferred between pigments (called resonance energy transfer), where the excited electron in one pigment induce excitement in neighboring pigments until it reaches a reaction center.
At reaction center: contains chlorophyll P680 in PII or P700 in PI they become excited and release high energy electrons into a transport chain.
What happens to electrons that absorb a photon in the Reaction Centers, PSII
PSII: chlorophyll P680. When photon absorbed, it becomes excited leading to the transfer of an electron to an electron acceptor, called pheophytin. The high energy electron goes through an ETC associate with PSII including plastoquinone (PQ), cytochrome b6f and plastocyanin (PC). It pumps protons across the thylakoid membrane from the stroma into the thylakoid lumen. Eventually reach PSI where it replaces an electron that has been excited by another photon.
What happens to electrons that absorb a photon in the Reaction Centers, PSI
contains chlorophyl called P700. The high energy electron is received from PSII and is excited by another photon boosting it to a higher energy level. The excited electron is transferred through a second electron transport chain (ferredoxin (Fd) pathway). The electron passes through ferredoxin and reduces NADP+ to NADPH.
Draw the spatial organization of the proteins and cofactors in photosynthesis
on doc
Draw the electron flow for photosynthesis
on doc
Overall reactions of photosynthesis
6 CO2 + 6 Ribulose 1,5bisP (5-C) —> 12 3-phosphoglycerate (3-C)
—using rubisco
12 3-phosphoglycerate (3-C) —> 1 glucose (6-C) + 6 Ribulose 1,5bisP (5-C)
—-using other calvin cycle enzymes
Net:6 CO2 —> 1 glucose (6-C)
Function of plastocyanin (PC)
Its main function is to transfer electrons from the cytochrome b6f complex (cyt b6f) to photosystem I (PSI).
Plastoquinone (PQ) function
embedded in the thylakoid membrane.
It serves as a mobile electron carrier that shuttles electrons between photosystem II (PSII) and the cytochrome b6f complex (cyt b6f)
Ferredoxin (Fd)
-small iron protein in stoma of chloroplast
-Its primary role is to accept electrons from photosystem I (PSI) and transfer them to various downstream electron acceptors.
- its reaction center chlorophyll (P700), it transfers electrons to ferredoxin, reducing it (Fd^+).
-reduction of NADP+ to NADPH
Draw the Z scheme
on doc
Draw the two reactions of Rubisco
on doc
Why does oxygenase activity decrease plant productivity?
No added carbon so no new carbohydrates. Recycling 2-phosphoglycolate requires ATP
How C4 plants reduce oxygenase activity of Rubisco?
C4 plants: incorporate CO2 into 4-carbon molecule
–Atmospheric CO2is initially incorporated into oxaloacetate
–Tropical grasses, including maize and sugar cane
–Less susceptible to photorespiration
