49) 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?
A) The pH within the thylakoid is less than that of the stroma.
B) The pH of the stroma is lower than that of the other two measurements.
C) The pH of the stroma is higher than that of the thylakoid space but lower than that of the cytosol.
D) The pH of the thylakoid space is higher than that anywhere else in the cell.
E) There is no consistent relationship.
50) The phylogenetic distribution of the enzyme rubisco is limited to
A) C3 plants only.
B) C3 and C4 plants.
C) all photosynthetic eukaryotes.
D) all known photoautotrophs, both bacterial and eukaryotic.
E) all living cells.
51) Photorespiration occurs when rubisco reacts RuBP with
A) CO2.
B) O2.
C) glyceraldehyde 3-phosphate.
D) 3-phosphoglycerate.
E) NADPH.
52) In 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
A) C4 plant.
B) C3 plant.
C) CAM plant.
D) heterotroph.
E) chemoautotroph.
53) Why are C4 plants able to photosynthesize with no apparent photorespiration?
A) They do not participate in the Calvin cycle.
B) They use PEP carboxylase to initially fix CO2.
C) They are adapted to cold, wet climates.
D) They conserve water more efficiently.
E) They exclude oxygen from their tissues.
54) CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because
they
A) fix CO2 into organic acids during the night.
B) fix CO2 into sugars in the bundle-sheath cells.
C) fix CO2 into pyruvate in the mesophyll cells.
D) use the enzyme phosphofructokinase, which outcompetes rubisco for CO2.
E) use photosystem I and photosystem II at night.
55) Photorespiration lowers the efficiency of photosynthesis by
A) carbon dioxide molecules.
B) 3-phosphoglycerate molecules.
C) ATP molecules.
D) ribulose bisphosphate molecules.
E) RuBP carboxylase molecules.
56) The alternative pathways of photosynthesis using the C4 or CAM systems are said to be
compromises. Why?
A) Each one minimizes both water loss and rate of photosynthesis.
B) C4 compromises on water loss and CAM compromises on photorespiration.
C) Both minimize photorespiration but expend more ATP during carbon fixation.
D) CAM plants allow more water loss, while C4 plants allow less CO2 into the plant.
E) C4 plants allow less water loss but CAM plants allow more water loss.
57) If plant gene alterations cause the plants to be deficient in photorespiration, what would most
probably occur?
A) Photosynthetic efficiency would be reduced at low light intensities.
B) Cells would carry on the Calvin cycle at a much slower rate.
C) Less ATP would be generated.
D) There would be more light-induced damage to the cells.
E) Less oxygen would be produced.
58) Compared to C3 plants, C4 plants
A) can continue to fix CO2 even at relatively low CO2 concentrations and high oxygen concentrations.
B) have higher rates of photorespiration.
C) do not use rubisco for carbon fixation.
D) grow better under cool, moist conditions.
E) make a four-carbon compound, oxaloacetate, which is then delivered to the citric acid cycle in
mitochondria.
59) If atmospheric CO2 concentrations increase twofold or more, how will plants be affected,
disregarding any changes in climate?
A) All plants will experience increased rates of photosynthesis.
B) C3 plants will have faster growth; C4 plants will be minimally affected.
C) C4 plants will have faster growth; C3 plants will be minimally affected.
D) C3 plants will have faster growth; C4 plants will have slower growth.
E) Plant growth will not be affected because atmospheric CO2 concentrations are never limiting for
plant growth.
60) Plants photosynthesize only in the light. Plants respire
A) in the dark only.
B) in the light only.
C) both in light and dark.
D) never–they get their ATP from photophosphorylation.
E) only when excessive light energy induces photorespiration.
Art Questions
Figure 10.1
61) Figure 10.1 shows the absorption spectrum for chlorophyll a and the action spectrum for
photosynthesis. Why are they different?
A) Green and yellow wavelengths inhibit the absorption of red and blue wavelengths.
B) Bright sunlight destroys photosynthetic pigments.
C) Oxygen given off during photosynthesis interferes with the absorption of light.
D) Other pigments absorb light in addition to chlorophyll a.
E) Aerobic bacteria take up oxygen, which changes the measurement of the rate of photosynthesis.
62) What wavelength of light in the figure is most effective in driving photosynthesis?
A) 420 mm
B) 475 mm
C) 575 mm
D) 625 mm
E) 730 mm
Use the following figure and the compounds labeled A, B, C, D, and E to answer the following questions.
Figure 10.2
63) If ATP used by this plant is labeled with radioactive phosphorus, which molecule or molecules of
the Calvin cycle will be radioactively labeled first?
A) B only
B) B and C only
C) B, C, and D only
D) B and E only
E) B, C, D, and E
64) If the carbon atom of the incoming CO2 molecule is labeled with a radioactive isotope of carbon,
which organic molecules will be radioactively labeled after one cycle?
A) C only
B) B, C, D, and E
C) C, D, and E only
D) B and C only
E) B and D only
65) Which molecule(s) of the Calvin cycle is (are) also found in glycolysis?
A) B, C, E, and 3-phosphoglycerate
B) B, C, and E only
C) 3-phosphoglycerate only
D) B, C, D, and 3-phosphoglycerate only
E) E only
66) To identify the molecule that accepts CO2, Calvin and Benson manipulated the carbon-fixation
cycle by either cutting off CO2 or cutting off light from cultures of photosynthetic algae. They then
measured the concentrations of various metabolites immediately following the manipulation. How
would these experiments help identify the CO2 acceptor? Study Figure 10.2 to help you in determining
the correct answer.
A) The CO2 acceptor concentration would decrease when either the CO2 or light are cut off.
B) The CO2 acceptor concentration would increase when either the CO2 or light are cut off.
C) The CO2 acceptor concentration would increase when the CO2 is cut off, but decrease when the light
is cut off.
D) The CO2 acceptor concentration would decrease when the CO2 is cut off, but increase when the light
is cut off.
E) The CO2 acceptor concentration would stay the same regardless of the CO2 or light.
Figure 10.3
67) Which of the following statements is true concerning Figure 10.3?
A) It represents cell processes involved in C4 photosynthesis.
B) It represents the type of cell structures found in CAM plants.
C) It represents an adaptation that maximizes photorespiration.
D) It represents a C3 photosynthetic system.
E) It represents a relationship between plant cells that photosynthesize and those that cannot.
68) Referring to Figure 10.3, oxygen would inhibit the CO2 fixation reactions in
A) cell I only.
B) cell II only.
C) neither cell I nor cell II.
D) both cell I and cell II.
E) cell I during the night and cell II during the day.
Scenario Questions
69) A gardener is concerned that her greenhouse is getting too hot from too much light, and seeks to
shade her plants with colored translucent plastic sheets. What color should she use to reduce overall
light energy, but still maximize plant growth?
A) green
B) blue
C) yellow
D) orange
E) any color will work equally well
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.
70) What did Engelmann conclude about the congregation of bacteria in the red and blue areas?
A) Bacteria released excess carbon dioxide in these areas.
B) Bacteria congregated in these areas due to an increase in the temperature of the red and blue light.
C) Bacteria congregated in these areas because these areas had the most oxygen being released.
D) Bacteria are attracted to red and blue light and thus these wavelengths are more reactive than other
wavelengths.
E) Bacteria congregated in these areas due to an increase in the temperature caused by an increase in
photosynthesis.
71) An outcome of this experiment was to help determine
A) the relationship between heterotrophic and autotrophic organisms.
B) the relationship between wavelengths of light and the rate of aerobic respiration.
C) the relationship between wavelengths of light and the amount of heat released.
D) the relationship between wavelengths of light and the rate of photosynthesis.
E) the relationship between the concentration of carbon dioxide and the rate of photosynthesis.
72) If you ran the same experiment without passing light through a prism, what would you predict?
A) There would be no difference in results.
B) The bacteria would be relatively evenly distributed along the algal filaments.
C) The number of bacteria present would decrease due to an increase in the carbon dioxide
concentration.
D) The number of bacteria present would increase due to an increase in the carbon dioxide
concentration.
E) The number of bacteria would decrease due to a decrease in the temperature of the water.
A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system.
Plants will be grown to provide oxygen and to recycle carbon dioxide.
73) Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be
needed. What wavelengths of light should be used to maximize plant growth with a minimum of energy
expenditure?
A) full-spectrum white light
B) green light
C) a mixture of blue and red light
D) yellow light
E) UV light
74) If the power fails and the lights go dark, what will happen to CO2 levels?
A) CO2 will rise as a result of both animal and plant respiration.
B) CO2 will rise as a result of animal respiration only.
C) CO2 will remain balanced because plants will continue to fix CO2 in the dark.
D) CO2 will fall because plants will increase CO2 fixation.
E) CO2 will fall because plants will cease to respire in the dark.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 10
of the textbook.
75) The light reactions of photosynthesis supply the Calvin cycle with
A) light energy.
B) CO2 and ATP.
C) H2O and NADPH.
D) ATP and NADPH.
E) sugar and O2.
76) Which of the following sequences correctly represents the flow of electrons during photosynthesis?
A) NADPH → O2 → CO2
B) H2O → NADPH → Calvin cycle
C) NADPH → chlorophyll → Calvin cycle
D) H2O → photosystem I → photosystem II
E) NADPH → electron transport chain → O2
77) How is photosynthesis similar in C4 plants and CAM plants?
A) In both cases, only photosystem I is used.
B) Both types of plants make sugar without the Calvin cycle.
C) In both cases, rubisco is not used to fix carbon initially.
D) Both types of plants make most of their sugar in the dark.
E) In both cases, thylakoids are not involved in photosynthesis.
78) Which of the following statements is a correct distinction between autotrophs and heterotrophs?
A) Only heterotrophs require chemical compounds from the environment.
B) Cellular respiration is unique to heterotrophs.
C) Only heterotrophs have mitochondria.
D) Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients
that are inorganic.
E) Only heterotrophs require oxygen.
79) Which of the following does not occur during the Calvin cycle?
A) carbon fixation
B) oxidation of NADPH
C) release of oxygen
D) regeneration of the CO2 acceptor
E) consumption of ATP
80) In mechanism, photophosphorylation is most similar to
A) substrate-level phosphorylation in glycolysis.
B) oxidative phosphorylation in cellular respiration.
C) the Calvin cycle.
D) carbon fixation.
E) reduction of NADP+.
81) Which process is most directly driven by light energy?
A) creation of a pH gradient by pumping protons across the thylakoid membrane
B) carbon fixation in the stroma
C) reduction of NADP+ molecules
D) removal of electrons from chlorophyll molecules
E) ATP synthesis