BIOC 431 - Exam IV Questions with Verified Solutions Graded A+
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? - Answers 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? - Answers
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? - Answers 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? - Answers 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? - Answers 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? - Answers 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? -
Answers
Do you think the inner mitochondrial membrane is permeable to protons? How about the
thylakoid
membrane? Why might that be important? - Answers 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? - Answers 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.
- Answers 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. - Answers *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)
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? - Answers 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? - Answers
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? - Answers 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? - Answers 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? - Answers 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? - Answers 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? -
Answers
Do you think the inner mitochondrial membrane is permeable to protons? How about the
thylakoid
membrane? Why might that be important? - Answers 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? - Answers 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.
- Answers 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. - Answers *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)
