LS 7A Week 4 PAL
A large agricultural chemical company is testing a new experimental pesticide. An unfortunate
side effect in plants treated with this new product is a decrease in NADPH production in the
chloroplasts. (Interestingly, reduction of NAD+ to NADH in the mitochondria is unaffected.)
Given this observation, which of the answer choices would you expect to observe in the
chloroplasts of these plants?
a decrease in 3‐phosphoglycerate levels and an increase in RuBP levels
an increase in 3‐phosphoglycerate levels and an increase in RuBP levels
an increase in 3‐phosphoglycerate levels and a decrease in RuBP levels
an increase in glyceraldehyde‐3‐phosphate levels - ANS-an increase in 3‐phosphoglycerate
levels and a decrease in RuBP levels
explanation: 3-phosphoglycerate is reduced to G3P using ATP & NADPH, so if there is less
NADPH, less 3-phosphoglycerate be reduced so the levels will increase. RuBP is made in a
later step of the Calvin Cycle, so if there are precursors of RuBP being made due to the
decrease in NADPH, then levels of RuBP decrease.
Which answer choices could be true if a plant cell is exposed to a toxin that makes the thylakoid
membrane freely permeable to protons? Select all that apply.
There would be no ATP needed to split H2O molecules early in the light‐dependent pathway.
There would be no ATP available to drive carbohydrate synthesis in the Calvin cycle.
There would be no ATP produced in the chloroplasts to power photosynthesis in the absence of
light energy.
The amount of carbohydrate produced would increase.
ATP generated by the mitochondria would be used to power photosynthesis, so plant cells
would not have enough ATP left to supply the many other processes for which they require ATP.
The amount of NADPH in the chloroplast would increase. - ANS-There would be no ATP
available to drive carbohydrate synthesis in the Calvin cycle.
The amount of NADPH in the chloroplast would increase.
explanation: energy from ATP synthesis comes from the proton gradient. If the thylakoid
membrane is freely permeable to protons, there will be no concentration gradient to provide
energy to make ATP, which is required in the Calvin cycle.
In the Calvin cycle, ATP is needed before the step that requires NADPH, so NADPH will not end
up being used if the step requiring ATP doesn't occur. This will lead to an increasing amount of
NADPH in the chloroplast over time.
The concentration of ADP in a cell is increasing. Assuming that the cell has plenty of glucose
and oxygen available, carbon dioxide (CO2) production by the cell should:
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