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BIOC 431-Exam IV Questions and Answers
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BIOC 431-Exam IV Questions and Answers
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BIOC 431-Exam IV Questions andAnswers
Based on what you know about how plants store energy (starch), and the process of
photosynthesis, do
you think plants need mitochondria and its electron transport chain? - Answer-In order
to utilize starch as a form of energy, plants still need the Citric Acid Cycle, mitochondria,
and the ETC in order to produce ATP, a usable form of energy by the cell.
What is the ultimate electron donor and acceptor in chloroplasts? In mitochondria? -
Answer-chloroplasts- donor = water, acceptor = NADPH
mitochondria- donor = NADH , acceptor= O2
Is energy made or used in the electron transport chains (not ATP synthases) of
chloroplasts? of
mitochondria? - Answer-No, series of redox reactions that transfer electrons. In
chloroplasts the ETC makes energy in the form of NADPH as well as the proton motive
force. In mitochondria, energy is used as NADH as it is converted to NAD+. Another
way of looking at it--electrons in chloroplasts gain energy from beginning to end of
chain--positive to negative electric potential--whereas in mitochondria, energy is lost as
electrons lose energy from beginning to end--negative to positive electric potential.
What does the "Z" shape of the "Z scheme" represent? Why doesn't the mitochondrial
electron transport
chain have a Z shape? - Answer-The "Z scheme" represents the pathway of electron
transfer from H2O to NADP in noncyclic photosynthesis. The vertical scale of each
electron carrier reflects it's standard reduction potential. Each electron must be lifted
twice in order to raise the energy of electrons derived from H2O to the energy level
required to reduce NADP+.
How are photosystems II and I connected? - Answer-They are connected lipid and
water soluble electron carriers (plastoquinone, cytb6f complex, plastocyanin).
Why don't the components of either electron transport chain have to be next to each
other, or in a line? - Answer-Because they are connected by water soluble and lipid
soluble that move through or around the membranes
How is this convenient for keeping ATP synthase from taking up useful light‐absorbing
area? - Answer-
Do you think the inner mitochondrial membrane is permeable to protons? How about
the thylakoid
membrane? Why might that be important? - Answer-No, in order to maintain a gradient
across the mitochondrial membrane and thylakoid membrane, the membrane must be
, impermeable to protons except for electron proton complexes that transfer electrons
and establish a gradient.
What is the difference in the proton motive force between the thylakoid and
mitochondrial inner
membrane? - Answer-thylakoid:
deltapH = higher
delta psi = lower
3 ATP per 2 H2O oxidized
due to different amounts of other ions pumped
What is glutathione? How does it help us to recover from production of reactive oxygen
species. - Answer-A substance that can be reduced by NADPH to reduce oxygen
species. ROS recovery sacrifices electrochemical potential.
List the similarities and differences between the mitochondrial electron transport chain
and the photosynthetic electron transport chain. - Answer-*Mitochondrial ETC
Starts with NADH, ends by turning O2 into H2O.
Exists on a partially enclosed membrane
(porins)
"Downhill" scheme
Strongest redox carriers NADH and O2.
Energy stored primarily as delta psi
Has glutathione
*Photosynthetic ETC
Starts by taking electrons from H2O to make O2.
Exists on a completely enclosed membrane
(inside permeability barrier)
"Z scheme"
Strongest redox carriers chlorophyll and
activated chlorophyll.
Energy stored primarily as delta pH
Has many, diverse groups of antioxidants
*BOTH
Give five general classes of electron carriers that function in both mitochondrial
electron transfer to O2 and photosynthetic electron transfer. - Answer-Other e‐ carriers
similar
Similar electron transport chains: lipid soluble and aqueous soluble steps, 3 protein
complexes.
Both store energy across the membrane
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