chapter 10
What wavelength of light in the figure is most effective in driving photosynthesis?
420 mm
What are the products of linear photophosphorylation?
ATP and NADPH
What are the products of the light reactions that are subsequently used by the Calvin cycle?
ATP and NADPH
Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
ATP and NADPH
The light reactions of photosynthesis supply the Calvin cycle with
ATP and NADPH.
A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?
blue and violet
In metabolic processes of cell respiration and photosynthesis, prosthetic groups such as heme and iron-sulfur complexes are encountered. What do they do?
both oxidize and reduce during electron transport
Generation of proton gradients across membranes occurs during
both photosynthesis and respiration.
Synthesis of ATP by the chemiosmotic mechanism occurs during
both photosynthesis and respiration.
Which of the following statements is a correct distinction between autotrophs and heterotrophs?
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO₂ and other nutrients that are inorganic.
n an experiment studying photosynthesis performed during the day, you provide a plant with radioactive carbon (14c) dioxide as a metabolic tracer. The 14c is incorporated first into oxaloacetate. The plant is best characterized as a
C₄ plant.
Which of the events listed below occur in the light reactions of photosynthesis?
Light is absorbed and funneled to reaction-center chlorophyll a.
If photosynthesizing green algae are provided with synthesized with heavy oxygen later analysis will show that all but one of the following compounds produced by the algae contain the label. That one is
O2
Figure 10.1 shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?
Other pigments absorb light in addition to chlorophyll a
Referring to Figure 10.3, oxygen would inhibit the CO2 fixation reactions in
cell II only
As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find 30,000 molecules of ATP consumed, but only 20,000 molecules of NADPH. Where did the extra ATP molecules come from?
cyclic electron flow
Reduction of NADP+ occurs during
Photosynthesis
Which of the following statements best describes the relationship between photosynthesis and respiration?
Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.
Some photosynthetic bacteria (e.g., purple sulfur bacteria) have photosystem I but not II, while others (e.g. cyanobacteria) have both PSI and PSII. Which of the following might this observation imply?
Photosynthesis with only photosystem I is more ancestral.
Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?
The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, Pi, and NADP⁺ to the light reactions.
In a protein complex for the light reaction (a reaction center), energy is transferred from pigment molecule to pigment molecule, to a special chlorophyll a molecule, and eventually to the primary electron acceptor. Why does this occur?
The molecular environment lets it boost an electron to a higher energy level and also to transfer the electron to another molecule.
The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?
The pH within the thylakoid is less than that of the stroma.
If plant gene alterations cause the plants to be deficient in photorespiration, what would most probably occur?
There would be more light-induced damage to the cells.
What is the relationship between wavelength of light and the quantity of energy per photon?
They are inversely related.
Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?
They protect against oxidative damage from excessive light energy.
why are C4 plants able to photosynthesize with no apparent photorespiration?
They use PEP carboxylase to initially fix CO₂.
P680+ is said to be the strongest biological oxidizing agent. Why?
This molecule has a stronger attraction for electrons than oxygen, to obtain electrons from water.
In any ecosystem, terrestrial or aquatic, what group(s) is (are) always necessary?
autotrophs
CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they
fix CO₂ into organic acids during the night.
In the thylakoid membranes, what is the main role of the antenna pigment molecules?
harvest photons and transfer light energy to the reaction-center chlorophyll
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Produces NADPH
light reactions alone
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Produces molecular oxygen
light reactions alone
The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during
neither photosynthesis nor respiration.
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Produces NADH
neither the light reactions nor the Calvin cycle
In thylakoids, protons travel through ATP synthase from the stroma to the thylakoid space. Therefore the catalytic "knobs" of ATP synthase would be located
on the stromal side of the membrane.
In mechanism, photophosphorylation is most similar to
oxidative phosphorylation in cellular respiration.
Reduction of NADP+ occurs during
photosynthesis.
Which of the following are directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be
to test for liberation of O₂ in the light.
Cyclic electron flow may be photoprotective (protective to light-induced damage). Which of the following experiments could provide information on this phenomenon?
use mutated organisms that can grow but that cannot carry out cyclic flow of electrons and compare their abilities to photosynthesize in different light intensities against those of wild-type organisms
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
H₂O → NADPH → Calvin cycle
How is photosynthesis similar in C₄ plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially.
What does the chemiosmotic process in chloroplasts involve?
establishment of a proton gradient across the thylakoid membrane
Photorespiration lowers the efficiency of photosynthesis by preventing the formation of
sugar molecules
What is the primary function of the Calvin cycle?
synthesize simple sugars from carbon dioxide
Use the following information to answer the questions below. Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light. What did Engelmann con
Bacteria congregated in these areas because these areas had the most oxygen being released.
The alternative pathways of photosynthesis using the CO2 or CAM systems are said to be compromises. Why?
Both minimize photorespiration but expend more ATP during carbon fixation.
In which cell would you expect photorespiration?
Cell II
Which statement describes the functioning of photosystem II?
The P680 chlorophyll donates a pair of protons to NADPH, which is thus converted to NADP
Compared with the lines for chlorophyll a in the figure, where would you expect to find the lines to differ for chlorophyll b?
The absorption spectrum line would be lowest for chlorophyll b somewhat to the right of that for chlorophyll a (500—600).
Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light. If you ran the same experiment without passing light through a prism, what would you predict?
The bacteria would be relatively evenly distributed along the algal filaments.
The sugar that results from three "turns" of the Calvin cycle is glyceraldehyde-3-phosphate (G3P). Which of the following is a consequence of this?
The formation of sucrose and starch in plants involves assembling G3P molecules, with or without further rearrangements.
Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH-8 solution. What would be likely to happen?
The isolated chloroplasts will make ATP.
If ATP used by this plant is labeled with radioactive phosphorus, in which molecules will the radioactivity be measurable after one "turn" of the cycle?
in B and E only
If the carbon atom of the incoming CO2 molecule is labeled with a radioactive isotope of carbon, where will the radioactivity be measurable after one cycle?
in B, D and E only
In autotrophic bacteria, where are the enzymes located that can carry on organic synthesis?
in the cytosol
In the process of carbon fixation, RuBP attaches a CO2 to produce a 6 carbon molecule, which is then split in two. After phosphorylation and reduction, what more needs to happen in the Calvin cycle?
regeneration of RuBP
Which of the following does not occur in the Calvin cycle?
release of oxygen
Which process is most directly driven by light energy?
removal of electrons from chlorophyll molecules
Reduction of oxygen which forms water occurs during
respiration
When oxygen is released as a result of photosynthesis, it is a by-product of which of the following?
splitting water molecules.
Where do the enzymatic reactions of the Calvin cycle take place?
stroma of the chloroplast
Where does the Calvin cycle take place?
stroma of the chloroplast
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Produces three-carbon sugars
the Calvin cycle
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Requires ATP
the Calvin cycle alone
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Requires CO2
the Calvin cycle alone
For the following questions, compare the light reactions with the Calvin cycle of photosynthesis in plants. Requires glucose
the calvin cycle alone
Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light. An outcome of this experiment was to help determine
the relationship between wavelengths of light and the rate of photosynthesis.
In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from
the stroma to the thaylakoid space
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will have the most direct effect on which of the following processes?
the synthesis of ATP
The reaction-center chlorophyll of photosystem I is known as P700 because
this pigment is best at absorbing light with a wavelength of 700 nm
In a plant cell, where are the ATP synthase complexes located?
thylakoid membrane and inner mitochondrial membrane
Where are the molecules of the electron transport chain found in plant cells?
thylakoid membranes of chloroplasts