Campbell Biology Chapter 33 Quiz and
Study Guide 2025
What are the products of linear photophosphorylation?
A) heat and fluorescence
B) ATP and P700
C) ATP and NADPH
D) ADP and NADP
E) P700 and P680
Rationale: Linear photophosphorylation uses both photosystem II and I, producing ATP and
NADPH as energy carriers for the Calvin cycle.
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?
A) photosystem II
B) photosystem I
C) cyclic electron flow
D) linear electron flow
E) chlorophyll
Rationale: Cyclic electron flow produces additional ATP without generating NADPH,
compensating for the Calvin cycle’s higher ATP demand.
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 process?
A) the splitting of water
B) the absorption of light energy by chlorophyll
C) the flow of electrons from photosystem II to photosystem I
D) the synthesis of ATP
E) the reduction of NADP+
Rationale: ATP synthesis relies on the proton gradient across the thylakoid membrane. A
puncture dissipates the gradient, halting ATP production.
What does the chemiosmotic process in chloroplasts involve?
A) establishment of a proton gradient across the thylakoid membrane
B) diffusion of electrons through the thylakoid membrane
C) reduction of water to produce ATP energy
D) movement of water by osmosis into the thylakoid space from the stroma
E) formation of glucose, using carbon dioxide, NADPH, and ATP
Rationale: Chemiosmosis depends on the proton gradient across the thylakoid membrane, which
drives ATP synthase.
,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 likely happen?
A) The isolated chloroplasts will make ATP.
B) The Calvin cycle will be activated.
C) Cyclic photophosphorylation will occur.
D) The isolated chloroplasts will generate oxygen gas.
E) The isolated chloroplasts will reduce NADP+ to NADPH.
Rationale: A proton gradient across the membrane is enough to drive ATP synthase, even
without light, as long as ATP synthase is intact.
In a plant cell, where are the ATP synthase complexes located?
A) thylakoid membrane only
B) plasma membrane only
C) inner mitochondrial membrane only
D) thylakoid membrane and inner mitochondrial membrane
E) thylakoid membrane and plasma membrane
Rationale: Plant cells generate ATP in both chloroplasts (thylakoid membranes) and
mitochondria (inner membrane).
In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane
space, whereas in chloroplasts, chemiosmosis translocates protons from
A) the stroma to the photosystem II
B) the matrix to the stroma
C) the stroma to the thylakoid space
D) the intermembrane space to the matrix
E) the thylakoid space to the stroma
Rationale: In chloroplasts, protons are pumped into the thylakoid space, creating a gradient that
powers ATP synthase.
Which of the following statements best describes the relationship between photosynthesis and
respiration?
A) Respiration runs the biochemical pathways of photosynthesis in reverse.
B) Photosynthesis stores energy in complex organic molecules, whereas respiration releases
it.
C) Photosynthesis occurs only in plants and respiration occurs only in animals.
D) ATP molecules are produced in photosynthesis and used up in respiration.
E) Respiration is anabolic and photosynthesis is catabolic.
Rationale: Photosynthesis is anabolic (storing energy), while respiration is catabolic (releasing
stored energy).
Where are the molecules of the electron transport chain found in plant cells?
A) thylakoid membranes of chloroplasts
B) stroma of chloroplasts
C) outer membrane of mitochondria
D) matrix of mitochondria
,E) cytoplasm
Rationale: The photosynthetic electron transport chain is embedded in the thylakoid membrane.
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during
A) photosynthesis only
B) respiration only
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration only
Rationale: Chemiosmosis is a universal mechanism in both chloroplasts and mitochondria for
ATP production.
Reduction of oxygen to form water occurs during
A) photosynthesis only
B) respiration only
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration only
Rationale: Oxygen acts as the final electron acceptor in mitochondrial respiration, forming
water.
Reduction of NADP+ occurs during
A) photosynthesis
B) respiration
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration
Rationale: Photosystem I reduces NADP+ to NADPH during the light reactions.
The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during
A) photosynthesis
B) respiration
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration
Rationale: Oxygen comes from the splitting of water, not CO₂, in photosynthesis.
Generation of proton gradients across membranes occurs during
A) photosynthesis
B) respiration
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration
Rationale: Both chloroplasts and mitochondria rely on proton gradients to power ATP synthase.
, What is the relationship between wavelength of light and the quantity of energy per photon?
A) They have a direct, linear relationship.
B) They are inversely related.
C) They are logarithmically related.
D) They are separate phenomena.
E) They are only related in certain parts of the spectrum.
Rationale: The shorter the wavelength, the higher the energy of a photon (E = hc/λ).
What is the primary function of the light reactions of photosynthesis?
A) to produce NADPH and ATP that will power the Calvin cycle
B) to generate oxygen by fixing CO₂ into sugars
C) to convert glucose into pyruvate
D) to transport electrons directly to CO₂
E) to form starch granules for energy storage
Answer: A
Rationale: The light reactions capture light energy to make ATP and NADPH, which are
essential inputs for the Calvin cycle. Oxygen is released as a by-product, but not the main
purpose.
Why is cyclic electron flow important in photosynthesis?
A) It increases the production of NADPH
B) It produces extra ATP without making NADPH
C) It generates oxygen by splitting water
D) It fixes carbon directly into glucose
E) It replaces electrons lost by P680 in photosystem II
Answer: B
Rationale: Cyclic electron flow allows additional ATP to be produced to meet the high ATP
demand of the Calvin cycle, without making NADPH or oxygen.
Which pigment is directly involved in the light reactions of photosynthesis?
A) carotenoids
B) chlorophyll a
C) chlorophyll b
D) anthocyanins
E) xanthophylls
Answer: B
Rationale: Chlorophyll a is the primary pigment that participates directly in the light reactions,
while the others are accessory pigments that broaden the spectrum of light absorption.
Study Guide 2025
What are the products of linear photophosphorylation?
A) heat and fluorescence
B) ATP and P700
C) ATP and NADPH
D) ADP and NADP
E) P700 and P680
Rationale: Linear photophosphorylation uses both photosystem II and I, producing ATP and
NADPH as energy carriers for the Calvin cycle.
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?
A) photosystem II
B) photosystem I
C) cyclic electron flow
D) linear electron flow
E) chlorophyll
Rationale: Cyclic electron flow produces additional ATP without generating NADPH,
compensating for the Calvin cycle’s higher ATP demand.
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 process?
A) the splitting of water
B) the absorption of light energy by chlorophyll
C) the flow of electrons from photosystem II to photosystem I
D) the synthesis of ATP
E) the reduction of NADP+
Rationale: ATP synthesis relies on the proton gradient across the thylakoid membrane. A
puncture dissipates the gradient, halting ATP production.
What does the chemiosmotic process in chloroplasts involve?
A) establishment of a proton gradient across the thylakoid membrane
B) diffusion of electrons through the thylakoid membrane
C) reduction of water to produce ATP energy
D) movement of water by osmosis into the thylakoid space from the stroma
E) formation of glucose, using carbon dioxide, NADPH, and ATP
Rationale: Chemiosmosis depends on the proton gradient across the thylakoid membrane, which
drives ATP synthase.
,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 likely happen?
A) The isolated chloroplasts will make ATP.
B) The Calvin cycle will be activated.
C) Cyclic photophosphorylation will occur.
D) The isolated chloroplasts will generate oxygen gas.
E) The isolated chloroplasts will reduce NADP+ to NADPH.
Rationale: A proton gradient across the membrane is enough to drive ATP synthase, even
without light, as long as ATP synthase is intact.
In a plant cell, where are the ATP synthase complexes located?
A) thylakoid membrane only
B) plasma membrane only
C) inner mitochondrial membrane only
D) thylakoid membrane and inner mitochondrial membrane
E) thylakoid membrane and plasma membrane
Rationale: Plant cells generate ATP in both chloroplasts (thylakoid membranes) and
mitochondria (inner membrane).
In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane
space, whereas in chloroplasts, chemiosmosis translocates protons from
A) the stroma to the photosystem II
B) the matrix to the stroma
C) the stroma to the thylakoid space
D) the intermembrane space to the matrix
E) the thylakoid space to the stroma
Rationale: In chloroplasts, protons are pumped into the thylakoid space, creating a gradient that
powers ATP synthase.
Which of the following statements best describes the relationship between photosynthesis and
respiration?
A) Respiration runs the biochemical pathways of photosynthesis in reverse.
B) Photosynthesis stores energy in complex organic molecules, whereas respiration releases
it.
C) Photosynthesis occurs only in plants and respiration occurs only in animals.
D) ATP molecules are produced in photosynthesis and used up in respiration.
E) Respiration is anabolic and photosynthesis is catabolic.
Rationale: Photosynthesis is anabolic (storing energy), while respiration is catabolic (releasing
stored energy).
Where are the molecules of the electron transport chain found in plant cells?
A) thylakoid membranes of chloroplasts
B) stroma of chloroplasts
C) outer membrane of mitochondria
D) matrix of mitochondria
,E) cytoplasm
Rationale: The photosynthetic electron transport chain is embedded in the thylakoid membrane.
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during
A) photosynthesis only
B) respiration only
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration only
Rationale: Chemiosmosis is a universal mechanism in both chloroplasts and mitochondria for
ATP production.
Reduction of oxygen to form water occurs during
A) photosynthesis only
B) respiration only
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration only
Rationale: Oxygen acts as the final electron acceptor in mitochondrial respiration, forming
water.
Reduction of NADP+ occurs during
A) photosynthesis
B) respiration
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration
Rationale: Photosystem I reduces NADP+ to NADPH during the light reactions.
The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during
A) photosynthesis
B) respiration
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration
Rationale: Oxygen comes from the splitting of water, not CO₂, in photosynthesis.
Generation of proton gradients across membranes occurs during
A) photosynthesis
B) respiration
C) both photosynthesis and respiration
D) neither photosynthesis nor respiration
E) photorespiration
Rationale: Both chloroplasts and mitochondria rely on proton gradients to power ATP synthase.
, What is the relationship between wavelength of light and the quantity of energy per photon?
A) They have a direct, linear relationship.
B) They are inversely related.
C) They are logarithmically related.
D) They are separate phenomena.
E) They are only related in certain parts of the spectrum.
Rationale: The shorter the wavelength, the higher the energy of a photon (E = hc/λ).
What is the primary function of the light reactions of photosynthesis?
A) to produce NADPH and ATP that will power the Calvin cycle
B) to generate oxygen by fixing CO₂ into sugars
C) to convert glucose into pyruvate
D) to transport electrons directly to CO₂
E) to form starch granules for energy storage
Answer: A
Rationale: The light reactions capture light energy to make ATP and NADPH, which are
essential inputs for the Calvin cycle. Oxygen is released as a by-product, but not the main
purpose.
Why is cyclic electron flow important in photosynthesis?
A) It increases the production of NADPH
B) It produces extra ATP without making NADPH
C) It generates oxygen by splitting water
D) It fixes carbon directly into glucose
E) It replaces electrons lost by P680 in photosystem II
Answer: B
Rationale: Cyclic electron flow allows additional ATP to be produced to meet the high ATP
demand of the Calvin cycle, without making NADPH or oxygen.
Which pigment is directly involved in the light reactions of photosynthesis?
A) carotenoids
B) chlorophyll a
C) chlorophyll b
D) anthocyanins
E) xanthophylls
Answer: B
Rationale: Chlorophyll a is the primary pigment that participates directly in the light reactions,
while the others are accessory pigments that broaden the spectrum of light absorption.
