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Life: The Science of Biology, Ninth Edition
Sadava • Hillis • Heller • Berenbaum
Chapter 10: Photosynthesis: Energy from Sunlight
TEST FILE QUESTIONS
(By Catherine Ueckert)
Multiple Choice
1. Which of the following biological groups is dependent on photosynthesis for its
survival?
a. Vertebrates
b. Mammalia
c. Fishes
d. Plants
e. All of the above
Answer: e
Textbook Reference: 10.0 Photosynthesis and global climate change
Page: 189
Bloom’s Category: 2. Understanding
2. The Intergovernmental Panel of Climate Change, sponsored by the United Nations,
may be able to impact global climate change by
a. wavelengths of lights that are not part of the absorption spectrum.
b. light energy that is not absorbed.
c. inefficiency of light reactions that convert light to chemical energy.
d. reducing carbon dioxide emissions.
e. inefficiency chemical energy storage of photosynthetic products.
Answer: d
Textbook Reference: 10.0 Photosynthesis and global climate change
Page: 189
Bloom’s Category: 2. Understanding
3. As atmospheric CO2 rises globally, it is known there will be
a. an increase in photosynthetic rate.
b. an increase in temperature.
c. an increase in rainfall.
d. a decrease in temperature.
e. a decrease in rainfall.
Answer: a
Textbook Reference: 10:0 Photosynthesis and global climate change
Page: 189
Bloom’s Category: 2. Understanding
4. Global climate change may
a. increase photosynthetic rate.
b. increase plant growth.
c. change temperature throughout the globe.
d. necessitate a change in the crops grown.
e. All of the above
Answer: e
Textbook Reference: 10.0 Photosynthesis and global climate change
Page: 189
Bloom’s Category: 2. Understanding
5. Which of the following is the revised, balanced equation for the generation of sugar
from sunlight, water, and CO2?
a. 6 CO2 + 6 H2O → C6H12O6 + O2
b. 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O
c. 6 CO2 + 6 H2O → C6H12O6 + 6 O2
d. 12 CO2 + 12 H2O → 2 C6H12O6 + 2 O2
e. None of the above
Answer: b
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 190
Bloom’s Category: 2. Understanding
6. Which of the following statements about photosynthesis is false?
a. The water for photosynthesis in land plants comes primarily from the soil.
b. CO2 is taken in, and water and O2 are released through stomata.
c. Light is necessary for the production of O2 and carbohydrates.
d. Photosynthesis is the reverse of cellular respiration.
e. All the O2 gas produced during photosynthesis comes from water.
Answer: d
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 190–191
Bloom’s Category: 2. Understanding
7. The first phase of photosynthesis, a series of reactions that requires the absorption of
photons to form ATP and NADPH, is referred to as the _______ phase.
a. reduction
b. dark reactions
c. carbon fixation
d. light reactions (or photophosphorylation)
e. None of the above
Answer: d
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191
Bloom’s Category: 2. Understanding
8. Which of the following occurs during the light-independent reactions of
photosynthesis?
a. Water is converted into hydrogen and water.
b. CO2 is converted into sugars.
c. Chlorophyll acts as an enzyme.
d. Nothing occurs; the plant rests in the dark.
e. None of the above
Answer: b
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191
Bloom’s Category: 2. Understanding
9. When a suspension of algae is incubated in a flask in the presence of light and CO2 and
then transferred to the dark, the reduction of 3-phosphoglycerate to glyceraldehyde 3phosphate is blocked. This reaction stops when the algae are placed in the dark because
a. the reaction requires CO2.
b. the reaction is exergonic.
c. the reaction requires ATP and NADPH + H+.
d. the reaction requires O2.
e. chlorophyll is not synthesized in the dark.
Answer: c
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191
Bloom’s Category: 4. Analyzing
10. When a photon interacts with molecules such as those within chloroplasts, the
photons may
a. bounce off the molecules, having no effect.
b. pass through the molecules, having no effect.
c. be absorbed by the molecules.
d. Both a and c
e. All of the above
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 192
Bloom’s Category: 2. Understanding
11. Compared to long-wavelength photons, short-wavelength photons have
a. an insignificant amount of energy.
b. more energy.
c. energy not available to plant cells.
d. a ladder of energy.
e. an equal amount of energy.
Answer: b
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 192
Bloom’s Category: 2. Understanding
12. The wavelength of X rays is shorter than the wave length of infrared rays. Which of
the following is true?
a. X rays have more energy per photon than infrared rays have.
b. X rays have a smaller value for Planck’s constant than infrared waves have.
c. X rays have a different absorption spectrum than infrared waves have.
d. X rays and infrared waves have the same frequency.
e. Infrared waves are in the ground state, whereas X rays are in the excited state.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 192
Bloom’s Category: 4. Analyzing
13. A graph that plots the rate at which CO2 is converted to glucose versus the
wavelength of light illuminating a leaf is called
a. a Planck equation.
b. an absorption spectrum.
c. enzyme kinetics.
d. an electromagnetic spectrum.
e. an action spectrum.
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 1. Remembering
14. How do red and blue light differ from one another?
a. They differ in intensity.
b. They have a different number of photons in each quantum.
c. Their wavelengths are different.
d. They differ in duration.
e. Red is radiant, whereas blue is electromagnetic.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 2. Understanding
15. A molecule that has an absorption spectrum showing maximum absorption within the
wavelengths of visible light is
a. a reducing agent.
b. a quantum.
c. a photon.
d. electromagnetic radiation.
e. a pigment.
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 1. Remembering
16. When white light strikes a blue pigment, blue light is
a. reduced.
b. absorbed.
c. converted to chemical energy.
d. scattered or transmitted.
e. used to synthesize ATP.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 2. Understanding
17. Plants are green because
a. chlorophylls absorb blue and orange-red wavelengths of light and reflect green light.
b. chloroplasts transmit green light.
c. energized chlorophyll a emits green light.
d. plants do not possess green pigment.
e. chlorophylls absorb green light.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 2. Understanding
18. The energy difference between an electron excited by a photon and the electron in its
ground state is _______ of the photon.
a. less than the energy
b. greater than the energy
c. equal to the energy
d. related to the wavelength
e. Both c and d
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 2. Understanding
19. When a photon is absorbed by a molecule, the photon
a. loses its ability to generate any energy.
b. raises the molecule from a ground state of low energy to an excited state.
c. affects the molecule in ways that are not clearly understood.
d. causes a change in the velocity of the wavelengths.
e. None of the above
Answer: b
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 3. Applying
20. A range of energy that cannot be seen by human eyes but has slightly more energy
per photon than visible light is known as _______ radiation.
a. adaptive
b. solar
c. gamma
d. ultraviolet
e. None of the above
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 1. Remembering
21. The main photosynthetic pigments in plants are _______ and _______.
a. chlorophyll s; chlorophyll a
b. chlorophyll x; chlorophyll y
c. retinal pigment; accessory pigment
d. chlorophyll a; chlorophyll b
e. None of the above
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 1. Remembering
22. Why is the absorption spectrum of chlorophyll a not identical to the action spectrum
of photosynthesis?
a. Accessory pigments contribute energy to drive photosynthesis.
b. Chlorophyll a absorbs both red and blue light.
c. Chlorophyll a reflects green light.
d. Different wavelengths of light have different energies.
e. Chlorophyll a can be activated by absorbing a photon of light.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 2. Understanding
23. The photosynthetic pigment chlorophyll a absorbs
a. infrared light.
b. orange-red and blue light.
c. X rays.
d. gamma rays.
e. white light.
Answer: b
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 1. Remembering
24. Accessory pigments
a. play no role in photosynthesis.
b. transfer energy from chlorophyll to the electron transport chain.
c. absorb only the red wavelengths.
d. allow plants to absorb visible light of intermediate wavelengths.
e. transfer electrons to NADP.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 2. Understanding
25. What is the difference between chlorophyll a and chlorophyll b?
a. Chlorophyll a has a complex ring structure, whereas chlorophyll b has a linear
structure.
b. Chlorophyll a has a magnesium atom at its center, whereas chlorophyll b has a
phosphate group at its center.
c. Chlorophyll a has a methyl group, whereas chlorophyll b has an aldehyde group.
d. A hydrocarbon tail is found only in chlorophyll a.
e. Chlorophyll a fluoresces, whereas chlorophyll b passes the absorbed energy to another
molecule.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 4. Analyzing
26. When a photon is absorbed by chlorophyll,
a. the chlorophyll becomes “excited,” or energized.
b. a greater number of light wavelengths can be absorbed.
c. ATP is split into ADP, phosphate, and energy.
d. hydrogen ions are released.
e. the chlorophyll molecules fluoresce.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194–195
Bloom’s Category: 2. Understanding
27. The precise moment when light energy is captured in chemical energy is the point at
which
a. light shines on chlorophyll.
b. water is hydrolyzed.
c. chlorophyll is oxidized.
d. chlorophyll is reduced.
e. the CO2 from air is captured in a sugar.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 195
Bloom’s Category: 2. Understanding
28. In noncyclic photophosphorylation, water is used for the
a. hydrolysis of ATP.
b. excitation of chlorophyll.
c. reduction of chlorophyll.
d. oxidation of NADPH.
e. synthesis of chlorophyll.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 2. Understanding
29. In noncyclic photophosphorylation, electrons from _______ replenish chlorophyll
molecules that have given up electrons.
a. CO2
b. water
c. NADPH + H+
d. O2 gas
e. None of the above
Answer: b
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 2. Understanding
30. The O2 gas produced during photosynthesis is derived from
a. CO2.
b. glucose.
c. water.
d. CO.
e. bicarbonate ions.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 2. Understanding
31. The energy to hydrolyze water comes from
a. oxidized chlorophyll.
b. reduced chlorophyll.
c. the proton gradient.
d. ATP.
e. NADPH + H+.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 2. Understanding
32. Photosynthesis is the process that uses light energy to extract hydrogen atoms from
a. glucose.
b. chlorophyll.
c. CO2.
d. water.
e. None of the above
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 2. Understanding
33. The Z scheme is
a. the characteristic path of electrons when they are bounced out of the pigments of the
reaction center.
b. another name for the splitting of water.
c. the addition of CO2 to RuBP to form a six-carbon sugar.
d. the passing of high-energy electrons through ATP synthase.
e. the wavelengths of light absorbed by a specific molecule.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196–197
Bloom’s Category: 1. Remembering
34. The light energy absorbed by the P680 reaction center
a. oxidizes water.
b. removes a phosphate from ATP to form ADP.
c. fixes CO2 to form sugars.
d. is used to form rubisco.
e. is reflected and causes plants to appear green.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
35. In cyclic photophosphorylation, chlorophyll is reduced by
a. NADPH.
b. a chemiosmotic mechanism.
c. plastoquinone.
d. ATP.
e. hydrogen ions liberated by the splitting of a water molecule.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
36. Free energy is released in cyclic photophosphorylation
a. by the formation of ATP.
b. during the excitation of chlorophyll.
c. during the fluorescence of chlorophyll.
d. during each of the redox reactions of the electron transport chain.
e. when electrons are transferred from photosystem I to photosystem II.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
37. In noncyclic photophosphorylation, the chlorophyll in photosystem I returns to its
reduced state by
a. water.
b. accepting electrons from the transport chain of photosystem II.
c. two photons of light.
d. NADPH.
e. ATP.
Answer: b
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
38. The Calvin–Benson cycle uses more ATP than NADPH + H+. The needed ATP
comes from
a. the splitting of water.
b. the reduction of oxygen.
c. the oxidation of glucose.
d. cyclic P700.
e. noncyclic electronic transport.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
39. Cyclic electron transport
a. occurs when the ratio of NADPH + H+ to NADP+ in the chloroplasts of some
organisms is high.
b. is a series of redox reactions.
c. stores its released energy as a proton gradient.
d. is completed when the electron returns to P700+.
e. All of the above
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197–198
Bloom’s Category: 2. Understanding
40. During cyclic photophosphorylation, the energy to produce ATP is provided by
a. heat.
b. NADPH.
c. ground-state chlorophyll.
d. the redox reactions of the electron transport chain.
e. the Calvin–Benson cycle.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197–198
Bloom’s Category: 2. Understanding
41. Photophosphorylation provides the Calvin–Benson cycle with
a. protons and electrons.
b. CO2 and glucose.
c. water and photons.
d. light and chlorophyll.
e. ATP and NADPH.
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 2. Understanding
42. The enzyme ATP synthase couples the synthesis of ATP to
a. the diffusion of protons.
b. the reduction of NADP+.
c. the excitation of chlorophyll.
d. the reduction of chlorophyll.
e. CO2 fixation.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 1. Remembering
43. In both photosynthesis and respiration, protons are pumped across a membrane during
a. electron transport.
b. photolysis.
c. CO2 fixation.
d. reduction of O2.
e. glycolysis.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 4. Analyzing
44. The chemiosmotic hypothesis states that the energy for the production of ATP comes
from
a. the transfer of phosphate from intermediate compounds.
b. the reduction of NADP.
c. a proton gradient set up across the thylakoid membrane.
d. the oxidation of CO2.
e. Both a and b
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 1. Remembering
45. The net energy outcome of cyclic photophosphorylation is
a. ATP.
b. ATP and NADH.
c. NADPH.
d. ATP and NADPH.
e. sugar.
Answer: a
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 1. Remembering
46. Photosynthesis and respiration have which of the following in common?
a. In eukaryotes, both processes reside in specialized organelles.
b. ATP synthesis in both processes relies on the chemiosmotic mechanism.
c. Both use electron transport.
d. Both require light.
e. a, b, and c
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198–199
Bloom’s Category: 4. Analyzing
47. Which of the following scientific tools “cracked” the Calvin–Benson cycle?
a. Radioisotopes
b. Paper chromatography
c. Crystallography
d. Centrifugation and electron microscopy
e. Both a and b
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 199
Bloom’s Category: 1. Remembering
48. The energy source for the synthesis of carbohydrates in the Calvin cycle is
a. ATP only.
b. photons.
c. energized chlorophyll a.
d. NADPH + H+.
e. NADPH and ATP.
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 199
Bloom’s Category: 2. Understanding
49. The Calvin cycle uses _______ to produce glucose.
a. CO2
b. ATP
c. NADPH
d. rubisco
e. All of the above
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
Bloom’s Category: 2. Understanding
50. The enzyme rubisco is found in
a. chloroplasts.
b. mitochondria.
c. the cytoplasm.
d. the nucleus.
e. yeast.
Answer: a
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
Bloom’s Category: 1. Remembering
51. A suspension of algae is incubated in a flask in the presence of both light and CO2.
When it is transferred to the dark, the reduction of 3-phosphoglycerate to glyceraldehyde
3-phosphate is blocked, and the concentration of ribulose bisphosphate (RuBP) declines.
Why does the RuBP concentration decline?
a. Ribulose bisphosphate is synthesized from glyceraldehyde 3-phosphate.
b. Glyceraldehyde 3-phosphate is converted to glucose.
c. Ribulose bisphosphate is used to synthesize 3-phosphoglycerate.
d. Both a and b
e. Both a and c
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
Bloom’s Category: 4. Analyzing
52. During CO2 fixation, CO2 combines with
a. NADPH.
b. 3PG.
c. G3P.
d. water.
e. 1,5-ribulose bisphosphate.
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
Bloom’s Category: 1. Remembering
53. The NADPH required for the reduction of 3PG to G3P comes from
a. the dark reactions.
b. the light reactions.
c. the synthesis of ATP.
d. the Calvin cycle.
e. oxidative phosphorylation.
Answer: b
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
Bloom’s Category: 2. Understanding
54. The NADPH required for CO2 fixation is formed
a. by the reduction of O2.
b. by the hydrolysis of ATP.
c. during the light reactions.
d. in C4 plants only.
e. in the mitochondria.
Answer: c
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
Bloom’s Category: 2. Understanding
55. In bright light, the pH of the thylakoid space
a. can become more acidic.
b. can become more alkaline.
c. stays the same; the pH of the thylakoid space never changes.
d. can become neutral.
e. None of the above
Answer: a
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
Bloom’s Category: 1. Remembering
56. How many moles of CO2 must enter the Calvin–Benson cycle for the synthesis of one
mole of glucose?
a. 1
b. 2
c. 3
d. 6
e. 12
Answer: d
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
Bloom’s Category: 3. Applying
57. After the removal of carbon, the oxygen in CO2 ends up
a. as atmospheric oxygen.
b. attached to carbon and hydrogen to form sugar (G3P).
c. in the soil.
d. attached to hydrogen to form water.
e. as rubisco.
Answer: b
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
Bloom’s Category: 2. Understanding
58. When CO2 is added to RuBP, the first stable product synthesized is
a. pyruvate.
b. ribulose 1,5-bisphosphate.
c. 3PG.
d. ATP.
e. glyceraldehyde 3-phosphate (G3P).
Answer: c
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
Bloom’s Category: 2. Understanding
59. Heterotrophs are dependent on autotrophs for their food supply. Autotrophs can make
their own food by
a. feeding on bacteria and converting the nutrients into usable energy.
b. using light and simple chemicals to make reduced carbon compounds.
c. synthesizing it from water and CO2.
d. All of the above
e. None of the above
Answer: b
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
Bloom’s Category: 2. Understanding
60. How is the Calvin cycle connected to the light reactions?
a. The light-induced pH changes activate rubisco.
b. The light-induced electron flow changes the shape of four Calvin-cycle enzymes.
c. The Calvin cycle needs the ATP produced in the light reactions.
d. None of the above
e. All of the above
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201–202
Bloom’s Category: 2. Understanding
61. Photorespiration
a. results in CO2 fixation.
b. uses ATP and NADPH produced in the light reactions.
c. generates a proton gradient.
d. results in the synthesis of glucose.
e. All of the above
Answer: b
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202
Bloom’s Category: 2. Understanding
62. When RuBP reacts with O2,
a. it cannot react with CO2.
b. carbohydrate production increases.
c. plant growth is stimulated.
d. net carbon fixation increases by 25 percent.
e. two carbon molecules combine to form the four-carbon phosphoglycolate.
Answer: a
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202
Bloom’s Category: 2. Understanding
63. During photorespiration, rubisco uses _______ as a substrate.
a. CO2
b. O2
c. glyceraldehyde 3-phosphate
d. 3-phosphoglycerate
e. NADPH
Answer: b
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202
Bloom’s Category: 1. Remembering
64. Photorespiration reduces the net carbon fixed by the Calvin cycle by _______
percent.
a. 70
b. 25
c. 2.1
d. 0.21
e. 0.02
Answer: b
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202
Bloom’s Category: 1. Remembering
65. How does rubisco “decide” whether to act as an oxygenase or a carboxylase?
a. Rubisco has 10 times more affinity for O2 than CO2; therefore, it favors O2 fixation.
b. If O2 is relatively abundant, rubisco acts as a carboxylase.
c. If O2 predominates, rubisco fixes it and the Calvin–Benson cycle occurs.
d. Photorespiration is more likely at low temperatures.
e. As the ratio of CO2 to O2 falls in the leaf, the reaction of rubisco with O2 is favored,
and photorespiration proceeds.
Answer: e
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202–203
Bloom’s Category: 4. Analyzing
66. Photorespiration takes place in
a. mitochondria, chloroplasts and peroxisomes
b. chloroplasts and mitochondria
c. C4 plants only.
d. the microbodies.
e. the cytoplasm and peroxisomes
Answer: a
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203
Bloom’s Category: 2. Understanding
67. In C4 plants, CO2 is first fixed into a compound called
a. pyruvate.
b. glucose.
c. oxaloacetate.
d. ribulose bisphosphate.
e. 3-phosphoglycerate.
Answer: c
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203
Bloom’s Category: 1. Remembering
68. In C4 plants, the function of the four-carbon compound that is synthesized in the
mesophyll cells is to
a. reduce NADP+.
b. combine with CO2 to produce glucose.
c. carry CO2 to the bundle sheath cells.
d. drive the synthesis of ATP.
e. close the stomata.
Answer: c
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 204
Bloom’s Category: 2. Understanding
69. In C4 plants, starch grains are found in the chloroplasts of
a. the thylakoids.
b. mesophyll cells.
c. the intracellular space.
d. the stroma.
e. bundle sheath cells.
Answer: e
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 204
Bloom’s Category: 2. Understanding
70. The enzyme PEP carboxylase
a. can trap CO2 even at relatively low CO2 concentrations.
b. catalyzes the synthesis of RuBP.
c. catalyzes the synthesis of 3PG.
d. is found in the chloroplasts of bundle sheath cells.
e. couples the synthesis of ATP to the diffusion of protons.
Answer: a
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
Bloom’s Category: 2. Understanding
71. In cacti, CO2 is stored for use in the Calvin cycle
a. in the stems, roots, and leaves.
b. during the evening.
c. in glucose molecules.
d. in the stroma.
e. Both a and d
Answer: b
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
Bloom’s Category: 2. Understanding
72. If global climate change continues and CO2 levels continue to rise,
a. C4 plants will be favored.
b. C3 plants will have a comparative advantage.
c. More rice and wheat should be grown.
d. Photorespiration will increase.
e. Both b and c
Answer: e
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
Bloom’s Category: 2. Understanding
73. The level of atmospheric CO2 has varied considerably over the years. Currently, the
level of atmospheric CO2
a. is four times what is was during the time of the dinosaurs.
b. favors C4 plants under hot conditions.
c. has resulted in maximum CO2 fixation by rubisco.
d. is decreasing.
e. prevents the occurrence of photorespiration.
Answer: b
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
Bloom’s Category: 1. Remembering
74. Plants classified as CAM store CO2
a. by making oxaloacetate.
b. by making PEP carboxylase.
c. in malic acid.
d. in crassulacean acid.
e. Both a and c
Answer: e
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
Bloom’s Category: 2. Understanding
75. Photosynthesis takes place in plants only in the light. Respiration takes place
a. in the dark only.
b. in the light only.
c. in all organisms except plants.
d. both with and without light.
e. None of the above
Answer: d
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 205
Bloom’s Category: 2. Understanding
76. In plants, the reactions of glycolysis occur
a. in C3 plants only.
b. in the mitochondria.
c. in the chloroplasts.
d. only in the presence of light.
e. in the cytosol.
Answer: e
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 206
Bloom’s Category: 1. Remembering
77. Photosynthesis and respiration are linked through the
a. Calvin cycle.
b. citric acid cycle.
c. enzyme rubisco.
d. need for light.
e. a, b, and c
Answer: a
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 206
Bloom’s Category: 2. Understanding
78. Photosynthesis
a. uses 100 percent of the sunlight that reaches Earth.
b. is a very efficient biochemical pathway.
c. utilizes all wavelengths of light.
d. converts 90 percent of light energy to chemical energy.
e. utilizes only a small portion of the energy of sunlight.
Answer: e
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 206
Bloom’s Category: 2. Understanding
Fill in the Blank
1. _______ uses pipes to release CO2 around plants to research the effects of rising
atmospheric CO2 on photosynthesis and plant growth.
Answer: Free-air concentration enrichment, or FACE
Textbook Reference: 10.0 Photosynthesis and global climate change
Page: 189
Bloom’s Category: 1. Remembering
2. In the 1800s, the summarized chemical reaction for photosynthesis was incorrect
because it left out _______ as a product.
Answer: water
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 190
Bloom’s Category: 2. Understanding
3. Atmospheric CO2 enters plant leaves through openings called _______.
Answer: stomata
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191
Bloom’s Category: 1. Remembering
4. The light-independent reactions require the products of the _______ reactions.
Answer: light
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191
Bloom’s Category: 1. Remembering
5. Molecules that absorb wavelengths in the visible spectrum are called _______.
Answer: pigments
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 1. Remembering
6. The wide range of wavelengths that photons can have is shown by the _______.
Answer: electromagnetic spectrum
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193
Bloom’s Category: 1. Remembering
7. The molecular structure of chlorophyll a is (different from/similar to) _______ the
molecular structure of chlorophyll b.
Answer: similar to
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 2. Understanding
8. Carotenoids and phycobilins absorb photons between the red and blue wavelengths and
are known as _______.
Answer: accessory pigments
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
Bloom’s Category: 1. Remembering
9. In noncyclic photophosphorylation, the electrons for the reduction of chlorophyll in
photosystem II come from _______.
Answer: water
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 1. Remembering
10. NADP is the abbreviation for _______.
Answer: nicotinamide adenine dinucleotide phosphate
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196
Bloom’s Category: 1. Remembering
11. During the light reactions of photosynthesis, the synthesis of _______ is coupled to
the diffusion of protons.
Answer: ATP
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
12. The O2 found in Earth’s atmosphere is generated from photosystem _______ of
noncyclic photophosphorylation.
Answer: II
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 2. Understanding
13. The light-driven production of ATP from ADP and Pi in the chloroplast is a
chemiosmotic mechanism known as _______.
Answer: photophosphorylation
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 1. Remembering
14. During cyclic photophosphorylation, _______ rather than NADP+ receives the
electron from ferredoxin.
Answer: plastoquinone
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 1. Remembering
15. In both photosynthesis and respiration, _______ synthesis is coupled to the diffusion
of protons across a membrane.
Answer: ATP
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 2. Understanding
16. During cyclic photophosphorylation, the energy of photons is converted to the
chemical energy of the product, _______.
Answer: ATP
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 198
Bloom’s Category: 2. Understanding
17. A group of scientists led by _______ conducted experiments demonstrating that
RuBP is the CO2 acceptor in the dark reactions of photosynthesis.
Answer: Calvin
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 199
Bloom’s Category: 1. Remembering
18. The most abundant enzyme in the biosphere is _______.
Answer: rubisco (or RuBP carboxylase)
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 199
Bloom’s Category: 1. Remembering
19. Photosynthetic organisms that can harvest light to form carbohydrates are called
_______.
Answer: autotrophs
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
Bloom’s Category: 1. Remembering
20. During the process of _______, rubisco catalyzes the reaction of RuBP with oxygen.
Answer: photorespiration
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202
Bloom’s Category: 1. Remembering
21. When _______ are exposed to light and CO2, four-carbon compounds (oxaloacetate)
are the first carbon-containing products.
Answer: C4 plants
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203
Bloom’s Category: 1. Remembering
22. In C3 plants, the Calvin–Benson cycle occurs in the chloroplasts of _______ cells,
whereas in C4 plants the cycle occurs in the _______ cells.
Answer: mesophyll; bundle sheath
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203
Bloom’s Category: 4. Analyzing
Diagram
1. Refer to the diagram below. The Ruben and Kamen experiments tracing isotopes of
oxygen through the process of photosynthesis proved that
a. all the oxygen gas produced during photosynthesis comes from water.
b. CO2 is the source of the oxygen released during photosynthesis.
c. the oxygen released by water is incorporated into glucose.
d. oxygen is needed to made rubisco.
e. NADPH is made during the Calvin cycle.
Answer: a
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191
Bloom’s Category: 2. Understanding
STUDY GUIDE QUESTIONS
(By Jacalyn Newman)
Knowledge and Synthesis
1. The main function of photosynthesis is the
a. consumption of CO2.
b. production of ATP.
c. conversion of light energy to chemical energy.
d. production of starch.
e. production of O2.
Answer: c
Feedback: Photosynthetic organisms, including but not limited to plants, are the only life
forms capable of trapping light energy and converting it to chemical energy. Because of
this they form the basis of many of Earth’s food chains.
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 190
2. Which of the following best represent the components that are necessary for
photosynthesis to take place?
a. Mitochondria, accessory pigments, visible light, water, and CO2
b. Chloroplasts, accessory pigments, visible light, water, and CO2
c. Mitochondria, chlorophyll, visible light, water, and O2
d. Chloroplasts, chlorophyll, visible light, water, and CO2
e. Chlorophyll, accessory pigments, visible light, water, and O2
Answer: d
Feedback: Chloroplasts are the site of the photosynthetic reactions; chlorophyll is excited
by photons of light and serves as reaction centers for the photosystems; visible light is
necessary to excite chlorophyll and accessory pigments; water is the initial electron donor
for the pathway; and CO2 is necessary to make precursor molecules for energy storage.
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 192
3. Chlorophyll is suited for the capture of light energy because
a. certain wavelengths of light raise it to an excited state.
b. in its excited state it gives off electrons.
c. its structure allows it to attach to thylakoid membranes.
d. it can transfer absorbed energy to another molecule.
e. All of the above
Answer: e
Feedback: The “tails” of chlorophyll molecules are associated with the thylakoid
membranes of the chloroplasts. This close membrane association assists with establishing
the proton-motive force that will drive ATP synthesis. When excited by light, the
chlorophyll moves into an excited state and passes electrons to acceptor molecules. This
begins to set up the proton gradient across the membrane that will drive ATP synthesis.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
4. Plants give off O2 because
a. O2 results from the incorporation of CO2 into sugars.
b. they do not respire; they photosynthesize.
c. water is the initial electron donor, leaving O2 as a photosynthetic by-product.
d. electrons moving down the electron chain bind to water, releasing O2.
e. O2 is synthesized in the Calvin cycle.
Answer: c
Feedback: Water is split at photosystem II to donate electrons to the reaction center. The
resulting protons are moved across the membrane to establish the proton-motive force,
and O2 is given off as a by-product.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196–197
5. Cyclic and noncyclic electron flow are used in plants to
a. meet the ATP demands of the Calvin cycle.
b. produce excess NADPH + H+.
c. synthesize proportional amounts of ATP and NADPH + H+ in the chloroplast.
d. consume the products of the Calvin cycle.
e. produce O2 for the atmosphere.
Answer: a
Feedback: ATP is required at higher levels in the Calvin cycle than NADPH + H+ is;
therefore, there must be a mechanism for producing additional ATP. Cyclic electron flow
provides that mechanism. If noncyclic electron flow were to be sped up to meet ATP
needs, an excess of NADPH + H+ would result. Shifting between cyclic and noncyclic
flow balances ATP/NADPH + H+ ratios. Oxygen gas is a by-product of the light
reactions, but its production is not the purpose of the reactions.
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
6. Which of the following statements concerning the light reactions of photosynthesis is
true?
a. Photosystem I cannot operate independently of photosystem II.
b. Photosystems I and II are activated by different wavelengths of light.
c. Photosystems I and II transfer electrons and create proton equilibrium across the
thylakoid membrane.
d. Photosystem I is more significant than Photosystem II.
e. Oxygen gas is a product of Photosystem I.
Answer: b
Feedback: Photosystems I and II operate depending on whether electron flow is cyclic or
noncyclic. Activity is controlled by the ATP levels in the chloroplast. Photosystem II is
activated by light of a higher energy level than photosystem I. Both photosystems transfer
electrons and create proton gradients across the thylakoid membranes; photosystem I
does this via the cyclic pathway. Water is split by a structure embedded in the
photosystem II complex.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 196–197
7. ATP is produced during the light reactions via
a. CO2 fixation.
b. chemiosmosis.
c. reduction of water.
d. glycolysis.
e. noncyclic electron flow from photosystem I.
Answer: b
Feedback: In the light reactions, ATP synthesis occurs when protons flow through an
ATP synthase channel protein in the thylakoid membrane. This is a chemiosmotically
driven process. Photosystem II is always involved, while Photosystem I participates via
cyclic electron transport only.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
8. Because of the properties of chlorophyll, plants need adequate _______ light to grow
properly.
a. green
b. blue and red
c. infrared
d. ultraviolet
e. blue and blue-green
Answer: b
Feedback: Chlorophyll and accessory pigments absorb light in the blue and red
wavelengths of visible light. Green light is reflected; therefore, plants appear green.
(Accessory pigments allow energy from additional wavelengths to be absorbed as well.)
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
9. Which of the following statements concerning the Calvin cycle is false?
a. Light energy is not required for the cycle to proceed.
b. CO2 is assimilated into sugars.
c. RuBP is regenerated.
d. It uses energy stored in ATP and NADPH + H+.
e. All of the above are false.
Answer: a
Feedback: Light energy is required for the Calvin cycle to proceed. ATP synthesis is
dependent on light energy, and the Calvin cycle is dependent on ATP.
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201
10. Which of the following statements concerning rubisco is true?
a. Rubisco is a carboxylase.
b. Rubisco preferentially binds to O2 over CO2.
c. Rubisco is absent from C4 and CAM plants.
d. Rubisco catalyzes the splitting in water to release O2.
e. Rubisco is more allosterically regulated by CO2.
Answer: a
Feedback: Rubisco, the most abundant enzyme on Earth, has both oxygenase and
carboxylase activities. It is present in C3, C4, and CAM plants and binds CO2 with greater
affinity than O2.
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 200, 202
11. Which of the following begins the Calvin cycle that results in the entire pathway
being carried out under environmental conditions?
a. 3PG is reduced to G3P using ATP and NADPH + H+.
b. RuBP is regenerated.
c. CO2 and RuBP join forming 3PG.
d. G3P is converted into glucose and fructose.
e. Any of the above; as a cycle, it can start at any point.
Answer: c
Feedback: The first step of the Calvin cycle is the fixation of CO2 into 3PG. This is the
regulatory step, and it requires ATP and NADPH + H+. While it is true that the Calvin
cycle is a cycle, there is a net consumption of CO2 for the purpose of building
carbohydrates.
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
12. The Calvin cycle results in the production of
a. glucose.
b. starch.
c. rubisco.
d. G3P.
e. ATP.
Answer: d
Feedback: The Calvin cycle produces only G3P, which can then be metabolized into
storage products like sugars and starch.
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
13. Which of the following statements regarding photorespiration is true?
a. Photorespiration is a metabolically expensive pathway.
b. Photorespiration is avoided when CO2 levels are low.
c. Photorespiration increases the overall CO2 that is converted to carbohydrates.
d. Photorespiration increases by 75 percent the net carbon that is fixed.
e. Photorespiration is most common in C4 plants.
Answer: a
Feedback: Photorespiration uses as much ATP as photo-synthesis, but results in no
energy gains for the plant and reduces net carbon fixation by 25 percent compared with
the Calvin cycle. If CO2 is abundant, rubisco acts as a carboxylase rather than an
oxygenase.
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202–203
14. The fixation of CO2 by PEP carboxylase functions to
a. concentrate O2 for use in photosynthetic cells.
b. allow plants to close stomata without the occurrence of photorespiration.
c. allow plants to photosynthesize in the dark.
d. reduce water loss by the plant.
e. All of the above
Answer: b
Feedback: Plants do not photosynthesize in the dark. PEP carboxylase allows the fixation
of CO2 at low concentrations in the leaf so that it can be sent to rubisco for the Calvin
cycle.
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 204
15. CAM plants differ from C4 plants in that
a. photosynthesis can occur at night in CAM plants.
b. CO2 is stored in CAM plants as malic acid.
c. the stomata of CAM plants close during periods that favor photorespiration.
d. CAM plants use PEP carboxylase to fix CO2.
e. the Calvin cycle is only found in C4 and C3 plants, not in CAM plants.
Answer: b
Feedback: CAM plants functionally store CO2 as malic acid.
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203–204
16. Which of the following statements regarding the relationship between photosynthesis
and cellular respiration in plants is true?
a. Photosynthesis occurs in specialized photosynthetic cells.
b. Cellular respiration occurs in specialized respiratory cells.
c. Cellular respiration and photosynthesis can occur in the same cell.
d. Photosynthesis is limited to specialized plant cells and cellular respiration does not
occur in plant cells.
e. Both a and c
Answer: e
Feedback: Photosynthesis occurs only in plant cells that have the necessary structures,
but cellular respiration occurs in every living plant cell that has mitochondria and O2.
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 205–206
17. Photosynthesis occurs
a. in all plant cells.
b. only in photosynthetic plant cells.
c. only in plant cells lacking mitochondria.
d. only in the stroma.
e. only in the thylakoid membrane.
Answer: b
Feedback: Photosynthesis is limited to photosynthetic plant cells. There are many plant
cells that are not exposed to light or that lack chloroplasts; these cells rely on cellular
respiration.
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 192
18. Activities such as amino acid synthesis and active transport in plant cells are powered
by
a. the light-dependent and light-independent reactions of photosynthesis.
b. ATP from the light reactions of photosynthesis.
c. ATP from fermentation.
d. ATP from glycolysis and cellular respiration.
e. All of the above
Answer: d
Feedback: Plant cells have mitochondria (see Figure 5.7) and rely on the processes of
glycolysis and cellular respiration to provide ATP for cellular activities. Photosynthesis
converts light energy into potential energy stored in chemical form, but that energy must
then be made usable by the cells. Plant cells release this stored energy via the catabolic
reactions covered in Chapter 9 (see Figure 9.14).
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 206
Application
1. Plants consume CO2 and give off O2. How is this possible if plants must also undergo
cellular respiration?
Answer: Plant cells undergo cellular respiration in all living cells. Therefore, all living
cells consume O2. Photosynthesis occurs in specialized cells that consume both CO2 and
O2. Because atmospheric O2 levels are high, excess O2 is available for the plant to utilize;
therefore, O2 continues to be emitted from the plant.
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 205–206
2. Why do plants undergo both the light reactions of photosynthesis and the Calvin cycle?
Why don’t they simply use the ATP produced in the light reactions of photosynthesis to
drive cellular processes?
Answer: The light reactions of photosynthesis produce ATP. ATP cannot be stored for
use later (such as when light is not available); therefore, there has to be a mechanism for
that energy to be stored. The Calvin cycle stores the energy in the chemical bonds of
G3P, which can be incorporated into carbohydrates for longer-term storage.
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200
3. Why do plants undergo both photosynthesis and cellular respiration, even in the
daytime? Why don’t they simply use the ATP produced in the light reactions of
photosynthesis to drive cellular processes?
Answer: Though photosynthesis produces all the necessary energy for a plant, a plant
cannot be continuously photosynthetically active. Therefore, a plant stores energy in
carbohydrates. Cellular respiration is necessary to break down stored carbohydrates.
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 205–206
4. Rubisco has both carboxylase and oxygenase activities. These processes compete with
each other. What determines which function the enzyme has? What conditions favor
photorespiration? What conditions favor photosynthesis?
Answer: Whether rubisco acts as a carboxylase or an oxygenase depends on the relative
ratio of O2 to CO2. At higher CO2 levels, it acts as a carboxylase. At low CO2 levels, it
acts as an oxygenase. Photorespiration is favored during hot, dry weather, which forces
the closing of stomata and leads to increases in O2 levels within the leaf. Photosynthesis
is favored when stomata can remain open and light intensity is optimal.
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 202–203
5. Compare and contrast C3, C4, and CAM plants.
Answer: Refer to Table 10.1 in your book.
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
6. The Calvin cycle was once referred to as the “dark” reactions of photosynthesis. Why
is this a misnomer?
Answer: Light is required for both the light reactions of photosynthesis and the Calvin
cycle. The Calvin cycle depends on the ATP generated during the light-dependent
reactions.
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 193
7. Explain the differences between cyclic and noncyclic electron flow. Why are both
processes necessary?
Answer: Noncyclic electron flow involves both photosystems I and II. It results in equal
amounts of ATP and NADPH being synthesized (see Figure 10.10). However more ATP
than NADPH is required for the Calvin cycle (see Figure 10.15). To provide the
additional ATP, Photosystem I sends electrons to the electron carrier ferredoxin in
electron transport chain driving ATP synthesis (see Figure 10.11). This cyclic pathway
provides the necessary ATP for the Calvin cycle to regenerate RuBP.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197–198
8. How do accessory pigments enhance photosynthetic activity in plants?
Answer: Accessory pigments allow utilization of light in many wavelengths of the visible
spectrum that could not be used by chlorophyll alone. The energy absorbed is channeled
to the reaction centers of the photosystems.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
9. Why are plants green?
Answer: The primary pigments in plants are chlorophylls. Chlorophylls absorb blue and
orange-red wavelengths of light and reflect green light, thus making plants appear green.
See the absorption spectra and action spectra of chlorophyll in Figure 10.6.
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194
TEXTBOOK SELF-QUIZ
1. In noncyclic photosynthetic electron transport, water is used to
a. excite chlorophyll.
b. hydrolyze ATP.
c. reduce Pi.
d. oxidize NADPH.
e. reduce chlorophyll.
Answer: e
2. Which statement about light is true?
a. An absorption spectrum is a plot of biological effectiveness versus wavelength.
b. An absorption spectrum may be a good means of identifying a pigment.
c. Light need not be absorbed to produce a biological effect.
d. A given kind of molecule can occupy any energy level.
e. A pigment loses energy as it absorbs a photon.
Answer: b
3. Which statement about chlorophylls is not true?
a. Chlorophylls absorb light near both ends of the visible spectrum.
b. Chlorophylls can accept energy from other pigments, such as carotenoids.
c. Excited chlorophyll can either reduce another substance or release light energy.
d. Excited chlorophyll cannot be an oxidizing agent.
e. Chlorophylls contain magnesium.
Answer: d
4. In cyclic electron transport,
a. oxygen gas is released.
b. ATP is formed.
c. water donates electrons and protons.
d. NADPH forms.
e. CO2 reacts with RuBP.
Answer: b
5. Which of the following does not happen in noncyclic electron transport?
a. Oxygen gas is released.
b. ATP forms.
c. Water donates electrons and protons.
d. NADPH forms.
e. CO2 reacts with RuBP.
Answer: e
6. In chloroplasts,
a. light leads to the flow of protons out of the thylakoids.
b. ATP is formed when protons flow into the thylakoid lumen.
c. light causes the thylakoid lumen to become less acidic than the stroma.
d. protons return passively to the stroma through protein channels.
e. proton pumping requires ATP.
Answer: d
7. Which statement about the Calvin cycle is not true?
a. CO2 reacts with RuBP to form 3PG.
b. RuBP forms by the metabolism of 3PG.
c. ATP and NADPH form when 3PG is oxidized.
d. The concentration of 3PG rises if the light is switched off.
e. Rubisco catalyzes the reaction of CO2 and RuBP.
Answer: d
8. In C4 photosynthesis,
a. 3PG is the first product of CO2 fixation.
b. rubisco catalyzes the first step in the pathway.
c. 4-carbon acids are formed by PEP carboxylase in bundle sheath cells.
d. photosynthesis continues at lower CO2 levels than in C3 plants.
e. CO2 released from RuBP is transferred to PEP.
Answer: d
9. Photosynthesis in green plants occurs only during the day. Respiration in plants occurs
a. only at night.
b. only when there is enough ATP.
c. only during the day.
d. all the time.
e. in the chloroplast after photosynthesis.
Answer: d
10. Photorespiration
a. takes place only in C4 plants.
b. includes reactions carried out in peroxisomes.
c. increases the yield of photosynthesis.
d. is catalyzed by PEP carboxylase.
e. is independent of light intensity.
Answer: b
BIOPORTAL DIAGNOSTIC QUIZ (Personalized Study Plan Quiz)
(By Richard McCarty)
1. In green plant photosynthesis, water is
a. oxidized to oxygen gas (O2) in the light.
b. reduced to hydrogen gas.
c. used to hydrolyze ATP.
d. oxidized to O2 in the dark.
e. an electron acceptor.
Answer: a
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 190–191
Bloom’s Category: 1. Remembering
2. Which of the following statements about the light-independent reactions of
photosynthesis is not correct?
a. The light-independent reactions refer to the pathways by which CO2 is reduced to
carbohydrates.
b. The light-independent reactions take place in the chloroplast stroma.
c. ATP is consumed by light-independent reactions.
d. NADPH is consumed by light-independent reactions.
e. The light-independent reactions operate in the dark.
Answer: e
Textbook Reference: 10.1 What Is Photosynthesis?
Page: 191–192
Bloom’s Category: 1. Remembering
3. The _______ of photosynthesis is similar to the _______ of chlorophylls.
a. action spectrum; fluorescence spectrum
b. absorption spectrum; action spectrum
c. action spectrum; absorption spectrum
d. absorption spectrum; fluorescence spectrum
e. None of the above
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 193–194
Bloom’s Category: 2. Understanding
4. Which of the following statements about the role of chlorophyll in photosynthesis is
false?
a. Chlorophyll appears green because it reflects green light.
b. Most of the chlorophyll in a plant functions to gather light.
c. Chlorophyll is present in all photosynthetic organisms.
d. Most of the chlorophyll in a plant participates in an oxidation/reduction reaction.
e. Chlorophyll contains Mg2+.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 194–195
Bloom’s Category: 1. Remembering
5. Which statement given below best characterizes the properties of a photosystem?
a. A photosystem consists of just antennae pigments.
b. Photosystems do not contain proteins.
c. A photosystem consists of just reaction center chlorophylls.
d. There is only one photosystem in green plants.
e. A photosystem is a complex of pigments, proteins, and a reaction center chlorophyll.
Answer: e
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 195
Bloom’s Category: 2. Understanding
6. Reaction center chlorophylls
a. undergo reduction when in the excited state.
b. become oxidized in the dark.
c. are oxidized when in the excited state.
d. have a different structure from most of the antennae chlorophylls.
e. are not involved in electron transport in photosynthesis.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 195–196
Bloom’s Category: 4. Analyzing
7. The products of noncyclic electron transport are
a. ATP.
b. NADP+ and ATP.
c. NADPH and ATP.
d. NADPH, O2, and ATP.
e. NADP+, O2, and ATP.
Answer: d
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197
Bloom’s Category: 1. Remembering
8. Cyclic electron transport
a. involves photosystem II.
b. results in the formation of NADPH.
c. is coupled to proton uptake into the thylakoid lumen.
d. requires the oxidation of water.
e. does not use the electron transport chain between the two photosystems.
Answer: c
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 197
Bloom’s Category: 4. Analyzing
9. The immediate source of energy for ATP synthesis in chloroplasts is
a. electron transport.
b. the electrochemical proton gradient.
c. light.
d. energized chlorophylls.
e. NADPH.
Answer: b
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197–198
Bloom’s Category: 4. Analyzing
10. The ultimate source of energy for ATP synthesis in chloroplasts is
a. electron transport.
b. the electrochemical proton gradient.
c. light.
d. energized chlorophylls.
e. NADPH.
Answer: c
Textbook Reference: 10.2 How Does Photosynthesis Convert Light Energy into Chemical
Energy?
Page: 197–198
Bloom’s Category: 4. Analyzing
11. In C3 photosynthesis, NADPH is used for the
a. reduction of O2 to water.
b. synthesis of ATP.
c. the regeneration phase of the Calvin cycle.
d. formation of 3-phosphoglycerate (3-PG).
e. reduction of 3-phosphoglycerate (3-PG).
Answer: e
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200–201
Bloom’s Category: 4. Analyzing
12. The major product of photosynthesis that is exported from the leaves to the rest of the
plant is
a. glucose.
b. amino acids.
c. starch.
d. sucrose.
e. nucleotides.
Answer: d
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 200–201
Bloom’s Category: 1. Remembering
13. In addition to driving the synthesis of ATP and the reduction of NADP+ to NADPH,
light stimulates the Calvin cycle by _______ and _______.
a. decreasing the pH of the stroma; reduction of some enzymes
b. increasing the pH of the stroma; reduction of some enzymes
c. increasing the pH of the stroma; oxidation of some enzymes
d. decreasing the pH of the stroma; oxidation of some enzymes
e. None of the above
Answer: b
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 201–202
Bloom’s Category: 2. Understanding
14. Photorespiration
a. decreases the efficiency of photosynthesis in C3 plants.
b. occurs at high rates in C4 plants.
c. is a result of the carboxylation of RuBP.
d. takes place entirely within chloroplasts.
e. is insensitive to the CO2 to O2 concentration ratio.
Answer: a
Textbook Reference: 10.3 How Is Chemical Energy Used to Synthesize Carbohydrates?
Page: 202–204
Bloom’s Category: 2. Understanding
15. Which of the following is not a characteristic of C4 plants?
a. C4 plants contain two different types of chloroplasts.
b. C4 plants contain RuBP carboxylase and PEP carboxylase.
c. The first product of photosynthesis in C4 plants is 3PG.
d. C4 plants are better adapted to hot climates than C3 plants.
e. C4 plants use the Calvin cycle.
Answer: c
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203–205
Bloom’s Category: 1. Remembering
16. C4 plants have _______ rates of _______ than C3 plants because the ratio of the
concentrations of CO2 to that of O2 is _______ in C4 plants.
a. lower; respiration; higher
b. lower; photorespiration; higher
c. higher; photorespiration; higher
d. lower; photorespiration; lower
e. lower; respiration; lower
Answer: b
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 203–205
Bloom’s Category: 2. Understanding
17. The concentration of CO2 in Earth’s atmosphere has increased over the past 200
years. If this trend continues, as seems likely, what could happen to photosynthesis?
Ignore global warming and assume that the content of oxygen in the atmosphere will not
change.
a. The net yield C3 photosynthesis should increase; C4 photosynthesis should be
unaffected.
b. The net yield C3 photosynthesis should decrease; C4 photosynthesis should be
unaffected.
c. The net yield C3 photosynthesis should stay the same; C4 photosynthesis should
increase.
d. Both the net yield C3 photosynthesis and C4 photosynthesis should not change.
e. None of the above
Answer: a
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 204
Bloom’s Category: 5. Evaluating
18. Plants that carry out crassulacean acid metabolism (CAM) differ from C4 plants in
that
a. they do not contain PEP carboxylase.
b. they do not carry out the Calvin cycle.
c. their stomates are open at night.
d they do not need ATP for photosynthesis.
e. they do not contain rubisco.
Answer: c
Textbook Reference: 10.4 How Do Plants Adapt to the Inefficiencies of Photosynthesis?
Page: 205
Bloom’s Category: 4. Analyzing
19. If you were to grow a green plant in a lighted chamber in the presence of radioactive
carbon dioxide for several days, which of the following types of compounds in the plant
would be radioactive?
a. Only sugars
b. Amino acids and proteins
c. Oils and membrane lipids
d. Calvin cycle intermediates
e. All of the above
Answer: e
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 205
Bloom’s Category: 5. Evaluating
20. Mesophyll cells of a leaf of a green plant
a. do not contain mitochondria.
b. cannot carry out glycolysis.
c. do not respire.
d. have metabolic pathways that are very similar to those in animal cells, except for
photosynthesis.
e. resemble prokaryotes.
Answer: d
Textbook Reference: 10.5 How Does Photosynthesis Interact with Other Pathways?
Page: 205
Bloom’s Category: 4. Analyzing