Chapter 10

8) Chlorophylls absorb most light in which colors of the visible range? A) green and blue B) blue and red C) green and red D) violet and red

Answer: B

28) Which statement describes the functioning of photosystem II? A) Light energy excites electrons in the thylakoid membrane electron transport chain. B) Photons are passed along to a reaction-center chlorophyll. C) The P680 chlorophyll donates a pair of protons to NADP+, which is thus converted to NADPH. D) The electron vacancies in P680+ are filled by electrons derived from water. E) The splitting of water yields molecular carbon dioxide as a by-product.

Answer: D

32) Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will most directly affect the ________. A) splitting of water B) absorption of light energy by chlorophyll C) flow of electrons from photosystem II to photosystem I D) synthesis of ATP E) reduction of NADP+

Answer: D

Use the following information to answer the question(s) below. A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the Sun for photosynthesis, an artificial light source will be needed. 56) If the power fails and the lights go dark, CO2 levels will ________. A) rise as a result of both animal and plant respiration B) rise as a result of animal but not plant respiration C) remain balanced because plants will continue to fix CO2 in the dark D) fall because plants will increase CO2 fixation E) fall because plants will cease to respire in the dark

Answer: A

11) In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and ________. A) carotenoids and other pigments are still present in the leaves B) the degraded chlorophyll changes into many other colors C) water supply to the leaves has been reduced D) sugars are sent to most of the cells of the leaves

Answer: A

21) The proteins of the electron transport chain active in the light-dependent reactions ________. A) are membrane proteins present in the thylakoid B) are free proteins present in the thylakoid lumen C) are considered to be part of the reaction center of photosystem I D) absorb the same wavelengths of light as their associated chlorophylls

Answer: A

33) The chemiosmotic process in chloroplasts involves the ________. 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 D) movement of water by osmosis into the thylakoid space from the stroma E) formation of glucose, using carbon dioxide, NADPH, and ATP

Answer: A

34) 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 most likely happen? A) The isolated chloroplasts would make ATP. B) The Calvin cycle would be activated. C) Cyclic photophosphorylation would occur. D) The isolated chloroplasts would generate oxygen gas. E) The isolated chloroplasts would reduce NADP+ to NADPH.

Answer: A

39) The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find? A) The pH within the thylakoid is less than that of the stroma. B) The pH of the stroma is lower than that of the other two measurements. C) The pH of the stroma is higher than that of the thylakoid space but lower than that of the cytosol. D) The pH of the thylakoid space is higher than anywhere else in the cell. E) There is no consistent relationship.

Answer: A

42) In plants, reduction of NADP+ occurs during ________. A) photosynthesis B) respiration C) photosynthesis and respiration D) neither photosynthesis nor respiration

Answer: A

44) Which of the following statements best represents the relationships between the light reactions and the Calvin cycle? A) The light reactions provide ATP and NADPH to the Calvin cycle, and the Calvin cycle returns ADP, i, and NADP+ to the light reactions. B) The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle, and the cycle provides water and electrons to the light reactions. C) The light reactions supply the Calvin cycle with CO2 to produce sugars, and the Calvin cycle supplies the light reactions with sugars to produce ATP. D) The light reactions provide the Calvin cycle with oxygen for electron flow, and the Calvin cycle provides the light reactions with water to split. E) There is no relationship between the light reactions and the Calvin cycle.

Answer: A

47) Photorespiration ________. A) generates carbon dioxide and consumes ATP and oxygen B) generates ATP and sugars and consumes oxygen and carbon dioxide C) generates oxygen and consumes ATP, carbon dioxide, and sugars D) consumes carbon dioxide and generates ATP, sugars, and oxygen

Answer: A

49) Where do the enzymatic reactions of the Calvin cycle take place? A) stroma of the chloroplast B) thylakoid membranes C) matrix of the mitochondria D) cytosol around the chloroplast E) thylakoid space

Answer: A

53) CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they ________. A) fix CO2 into organic acids during the night B) fix CO2 into sugars in the bundle-sheath cells C) fix CO2 into pyruvate in the mesophyll cells D) use the enzyme phosphofructokinase, which outcompetes rubisco for CO2 E) use photosystem I and photosystem II at night

Answer: A

Use the accompanying figure to answer the question(s) below. 20) What wavelength of light in the figure is most effective in driving photosynthesis? A) 420 mm B) 475 mm C) 575 mm D) 625 mm E) 730 mm

Answer: A

18) Use the following information to answer the question below. Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light. If you ran the same experiment as Engelmann without passing light through a prism, what would you predict? A) The results would be the same. B) The bacteria would be relatively evenly distributed along the algal filaments. C) The number of bacteria present would decrease due to an increase in the carbon dioxide concentration. D) The number of bacteria present would increase due to an increase in the carbon dioxide concentration. E) The number of bacteria would decrease due to a decrease in the temperature of the water.

Answer: B

43) How are the light-dependent and light-independent reactions of photosynthesis related? A) The products of light-independent reactions are used in light-dependent reactions. B) The products of light-dependent reactions are used in light-independent reactions. C) The products of light-independent reactions must be present for light-dependent reactions to take place. D) They are not related.

Answer: B

1) The process of photosynthesis probably originated ________. A) in plants B) in prokaryotes C) in fungi D) three separate times during evolution

Answer: B

10) Why are there several structurally different pigments in the reaction centers of photosystems? A) Excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain. B) This arrangement enables the plant to absorb light energy of a variety of wavelengths. C) They enable the plant to absorb more photons from light energy, all of which are at the same wavelength. D) They enable the reaction center to excite electrons to a higher energy level.

Answer: B

23) As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy? A) It excites electrons of the reaction center of photosystem I. B) It is lost as heat. C) It is used to establish and maintain a proton gradient. D) It is used to phosphorylate NAD+ to NADPH, the molecule that accepts electrons from photosystem I.

Answer: C

12) Energy from sunlight can excite electrons, kicking them out of their orbitals and creating free radicals. Free radicals are highly reactive atoms or molecules that have unpaired electrons and degrade and destroy other compounds in their vicinity. Carotenoids, one of the pigments present in most chloroplasts, can stabilize these free radicals. This suggests that ________. A) once chloroplasts are destroyed, the free radicals will destroy the cell B) carotenoids probably have a protective function in the cell C) free radicals induce the synthesis of carotenoids in chloroplasts D) carotenoids communicate directly with the immune system of plants

Answer: B

14) Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment? A) red and yellow B) blue and violet C) green and yellow D) blue, green, and red E) green, blue, and yellow

Answer: B

15) Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants? A) They serve as accessory pigments to increase light absorption. B) They protect against oxidative damage from excessive light energy. C) They shield the sensitive chromosomes of the plant from harmful ultraviolet radiation. D) They reflect orange light and enhance red light absorption by chlorophyll. E) They take up and remove toxins from the groundwater.

Answer: B

29) Which of the following are directly associated with photosystem I? A) harvesting of light energy by ATP B) receiving electrons from the thylakoid membrane electron transport chain C) generation of molecular oxygen D) extraction of hydrogen electrons from the splitting of water E) passing electrons to the cytochrome complex

Answer: B

30) Some photosynthetic organisms contain chloroplasts that lack photosystem II yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be to ________. A) determine if they have thylakoids in the chloroplasts B) test for liberation of O2 in the light C) test for CO2 fixation in the dark D) do experiments to generate an action spectrum E) test for production of either sucrose or starch

Answer: B

4) When oxygen is released as a result of photosynthesis, it is a direct by-product of ________. A) reducing NADP+ B) splitting water molecules C) chemiosmosis D) the electron transfer system of photosystem I E) the electron transfer system of photosystem II

Answer: B

40) In its mechanism, photophosphorylation is most similar to ________. A) substrate-level phosphorylation in glycolysis B) oxidative phosphorylation in cellular respiration C) the Calvin cycle D) carbon fixation E) reduction of NADP+

Answer: B

45) The light-independent reactions of plants function to make organic molecules using carbon dioxide as a carbon source. What is the electron source that helps reduce carbon dioxide to sugars and other organic molecules? A) NADH B) NADPH C) ATP D) electrons from oxygen

Answer: B

5) 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; respiration releases energy from complex organic molecules C) Photosynthesis occurs only in plants; respiration occurs only in animals. D) ATP molecules are produced in photosynthesis but not in aerobic respiration. E) Photosynthesis is catabolic; respiration is anabolic.

Answer: B

51) Reactions that require CO2 take place in ________. A) the light reactions alone B) the Calvin cycle alone C) both the light reactions and the Calvin cycle D) neither the light reactions nor the Calvin cycle E) the chloroplast, but not as part of photosynthesis

Answer: B

55) Use the accompanying figure and the molecules labeled A, B, C, D, and E to answer the following question. Refer to the figure. If the carbon atom of each of the incoming CO2 molecules is labeled with a radioactive isotope of carbon, which organic molecules will be radioactively labeled after one cycle? A) C only B) B, C, D, and E C) C, D, and E only D) B and C only E) B and D only

Answer: B

57) What would be the expected effect on plants if the atmospheric CO2 concentration was doubled? A) All plants would experience increased rates of photosynthesis. B) C3 plants would have faster growth; C4 plants would be minimally affected. C) C4 plants would have faster growth; C3 plants would be minimally affected. D) C3 plants would have faster growth; C4 plants would have slower growth. E) Plant growth would not be affected because atmospheric CO2 concentrations are never limiting for plant growth.

Answer: B

7) Which of the following sequences correctly represents the flow of electrons during photosynthesis? A) NADPH → O2 → CO2 B) H2O → NADPH → Calvin cycle C) NADPH → chlorophyll → Calvin cycle D) H2O → photosystem I → photosystem II E) NADPH → electron transport chain → O2

Answer: B

16) Plants photosynthesize ________. A) only in the light but respire only in the dark B) only in the dark but respire only in the light C) only in the light but respire in light and dark D) and respire only in the light E) and respire only in the dark

Answer: C

19) Use the following information to answer the question below. A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the Sun for photosynthesis, an artificial light source will be needed. What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure? A) full-spectrum white light B) green light C) a mixture of blue and red light D) yellow light E) UV light

Answer: C

22) What is the difference between NAD+ and NADP? A) NAD+ functions as an electron transporter, whereas NADP does not. B) NAD+ functions as a free-energy source for cells, whereas NADP does not. C) Both function as electron carriers, but NADP has a phosphate group and NAD+ does not. D) Both transport electrons to the electron transport chain (ETC) found on the inner mitochondrial membrane, but NADP transfers its electrons to the ETC at a higher energy level.

Answer: C

25) The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come? A) the electron carrier, plastocyanin B) photosystem I C) water D) oxygen

Answer: C

26) What is the main purpose of light-dependent reactions of photosynthesis? A) to generate oxygen by "splitting" H2O B) to produce NADPH for use in respiration C) to produce NADPH and ATP D) to use ATP to make glucose

Answer: C

31) As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. Where did the extra ATP molecules come from? A) photosystem II B) photosystem I C) cyclic electron flow D) linear electron flow E) chlorophyll

Answer: C

36) In mitochondria, chemiosmosis moves protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis moves protons from the ________. A) stroma to photosystem II B) matrix to the stroma C) stroma to the thylakoid space D) intermembrane space to the matrix E) thylakoid space to the stroma

Answer: C

38) The accumulation of free oxygen in Earth's atmosphere began with the origin of ________. A) life and respiratory metabolism B) photosynthetic bacteria that had photosystem I C) cyanobacteria using photosystem II D) chloroplasts in photosynthetic eukaryotic algae E) land plants

Answer: C

46) Which of the following procedures would identify the enzyme that catalyzes the carboxylation of ribulose-1,5-bisphosphate? A) irradiating a leaf extract with red light B) introducing radiolabeled carbon dioxide into a plant extract and determining which molecules become radiolabeled C) purifying a variety of proteins from plant extracts and testing each protein individually to see if it can carboxylate ribulose-1,5-bisphosphate D) differential sedimentation of a protein extract

Answer: C

54) The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why? A) Each one minimizes both water loss and rate of photosynthesis. B) C4 compromises on water loss and CAM compromises on photorespiration. C) Both minimize photorespiration but expend more ATP during carbon fixation. D) CAM plants allow more water loss, and C4 plants allow less CO2 into the plant. E) C4 plants allow less water loss, but CAM plants allow more water loss.

Answer: C

58) Use the accompanying figure and the molecules labeled A, B, C, D, and E to answer the following questions. Refer to the figure. To identify the molecule that accepts CO2, Calvin and Benson manipulated the carbon-fixation cycle by either cutting off CO2 or cutting off light from cultures of photosynthetic algae. They then measured the concentrations of various metabolites immediately following the manipulation. How would these experiments help identify the CO2 acceptor? A) The CO2 acceptor concentration would decrease when either the CO2 or light is cut off. B) The CO2 acceptor concentration would increase when either the CO2 or light is cut off. C) The CO2 acceptor concentration would increase when the CO2 is cut off but decrease when the light is cut off. D) The CO2 acceptor concentration would decrease when the CO2 is cut off but increase when the light is cut off. E) The CO2 acceptor concentration would stay the same regardless of the CO2 or light.

Answer: C

6) In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during ________. A) photosynthesis only B) respiration only C) photosynthesis and respiration D) neither photosynthesis nor respiration E) photorespiration only

Answer: C

13) What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)? A) ATP is synthesized from the energy absorbed. B) A carboxylation reaction of the Calvin cycle occurs. C) Electrons are stripped from NADPH. D) An electron is excited.

Answer: D

17) Use the accompanying figure to answer the question below. The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different? A) Green and yellow wavelengths inhibit the absorption of red and blue wavelengths. B) Bright sunlight destroys photosynthetic pigments. C) Oxygen given off during photosynthesis interferes with the absorption of light. D) Other pigments absorb light in addition to chlorophyll a. E) Aerobic bacteria take up oxygen, which changes the measurement of the rate of photosynthesis.

Answer: D

24) Plastoquinone (PQ), an electron carrier of small molecular weight, is found in the electron transport chain associated with photosystem II. If PQ is not directly anchored to other membrane or cytoplasmic structures, it is probably ________. A) mobile in the thylakoid membrane B) lipid soluble C) a molecule that serves as a shuttle between the electron transport chain and ATP synthase D) both lipid soluble and a molecule that serves as a shuttle between the electron transport chain and ATP synthase

Answer: D

35) 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

Answer: D

37) P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary? A) It is the receptor for the most excited electron in either photosystem of photosynthesis. B) It is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system. C) It transfers its electrons to reduce NADP+ to NADPH. D) It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has. E) It obtains carbon from a sugar molecule, so it must have a stronger attraction for electrons than either oxygen or hydrogen.

Answer: D

41) Which process is most directly driven by light energy? A) creation of a pH gradient by pumping protons across the thylakoid membrane B) carbon fixation in the stroma C) reduction of NADP+ molecules D) removal of electrons from chlorophyll molecules E) ATP synthesis

Answer: D

48) A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask. The dissolved oxygen in the flask with algae will ________. A) always be higher B) always be lower C) be higher in the light but the same in the dark D) be higher in the light but lower in the dark E) not be different from the control flask at any time

Answer: D

52) The phylogenetic distribution of the enzyme rubisco is limited to ________. A) only C3 plants B) C3 and C4 plants C) photosynthetic eukaryotes D) bacterial and eukaryotic photoautotrophs E) all living cells

Answer: D

9) Which of the following is a difference between chlorophyll a and chlorophyll b? A) Chlorophyll a is a pigment, and chlorophyll b is the enzyme that transfers excited electrons from chlorophyll a to electron carriers of the thylakoid membrane. B) Chlorophyll a absorbs yellow light, and chlorophyll b absorbs green. C) Chlorophyll a contains magnesium in its ring structure, whereas chlorophyll b contains iron. D) Chlorophyll a and b absorb light energy at slightly different wavelengths.

Answer: D

2) If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O EXCEPT ________. A) 3-phosphoglycerate B) glyceraldehyde 3-phosphate (G3P) C) glucose D) ribulose bisphosphate (RuBP) E) O2

Answer: E

27) Which of the events listed below occurs in the light reactions of photosynthesis? A) NADP is produced. B) NADPH is reduced to NADP+. C) Carbon dioxide is incorporated into PGA. D) ATP is phosphorylated to yield ADP. E) Light is absorbed and funneled to reaction-center chlorophyll a.

Answer: E

3) Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle? A) CO2 and glucose B) H2O and O2 C) ADP, i, and NADP+ D) electrons and H+ E) ATP and NADPH

Answer: E

50) What is the primary function of the Calvin cycle? A) using ATP to release carbon dioxide B) using NADPH to release carbon dioxide C) splitting water and releasing oxygen D) transporting RuBP out of the chloroplast E) synthesizing simple sugars from carbon dioxide

Answer: E