Deck 10: Photosynthesis: Energy From Sunlight

Question 1

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 1

D

Question 2

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 3-phosphate 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 2

C

Question 3

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 3

D

Question 4

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.

Question 5

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.

Question 6

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.

Question 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.

Question 8

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.

Question 9

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.

Question 10

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.

Question 11

In noncyclic photosynthetic electron transport, water is used to

A) excite chlorophyll.
B) hydrolyze ATP.
C) reduce P_i.
D) oxidize NADPH.
E) reduce chlorophyll.

Question 12

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.

Question 13

Which of the following is the revised, balanced equation for the generation of sugar from sunlight, water, and CO₂?

A) 6 CO₂ + 6 H₂O $\to$ C₆H₁₂O₆ + O₂
B) 6 CO₂ + 12 H₂O $\to$ C₆H₁₂O₆ + 6 O₂ + 6 H₂O
C) 6 CO₂ + 6 H₂O $\to$ C₆H₁₂O₆ + 6 O₂
D) 12 CO₂ + 12 H₂O $\to$ 2 C₆H₁₂O₆ + 2 O₂
E) None of the above

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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.

Question 19

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.

Question 20

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

Question 21

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.

Question 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.

Question 23

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.

Question 24

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.

Question 25

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.

Question 26

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.

Question 27

The photosynthetic pigment chlorophyll a absorbs

A) infrared light.
B) orange-red and blue light.
C) X rays.
D) gamma rays.
E) white light.

Question 28

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.

Question 29

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

Question 30

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.

Question 31

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.

Question 32

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.

Question 33

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.

Question 34

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

Question 35

The O₂ gas produced during photosynthesis is derived from

A) CO₂.
B) glucose.
C) water.
D) CO.
E) bicarbonate ions.

Question 36

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

Question 37

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

Question 38

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.

Question 39

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.

Question 40

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

Question 41

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.

Question 42

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

Question 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.

Question 44

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.

Question 45

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.

Question 46

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.

Question 47

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.

Question 48

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.

Question 49

The energy to hydrolyze water comes from

A) oxidized chlorophyll.
B) reduced chlorophyll.
C) the proton gradient.
D) ATP.
E) NADPH + H⁺.

Question 50

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

Question 51

The Calvin cycle uses _______ to produce glucose.

A) CO₂
B) ATP
C) NADPH
D) rubisco
E) All of the above

Question 52

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.

Question 53

The net energy outcome of cyclic photophosphorylation is

A) ATP.
B) ATP and NADH.
C) NADPH.
D) ATP and NADPH.
E) sugar.

Question 54

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.

Question 55

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

Question 56

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

Question 57

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.

Question 58

The enzyme rubisco is found in

A) chloroplasts.
B) mitochondria.
C) the cytoplasm.
D) the nucleus.
E) yeast.

Question 59

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.

Question 60

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

Question 61

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

Question 62

During photorespiration, rubisco uses _______ as a substrate.

A) CO₂
B) O₂
C) glyceraldehyde 3-phosphate
D) 3-phosphoglycerate
E) NADPH

Question 63

During CO₂ fixation, CO₂ combines with

A) NADPH.
B) 3PG.
C) G3P.
D) water.
E) 1,5-ribulose bisphosphate.

Question 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

Question 65

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

Question 66

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.

Question 67

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.

Question 68

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.

Question 69

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.

Question 70

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.

Question 71

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

Question 72

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

Question 73

In C₄ plants, CO₂ is first fixed into a compound called

A) pyruvate.
B) glucose.
C) oxaloacetate.
D) ribulose bisphosphate.
E) 3-phosphoglycerate.

Question 74

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.

Question 75

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

Question 76

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.

Question 77

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

Question 78

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).

Question 79

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.

Question 80

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