Chapter 10

20) What wavelength of light in the figure is most effective in driving photosynthesis?

A) 420 mm

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.

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.

42) In plants, reduction of NADP+ occurs during ________.

A) photosynthesis

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.

21) The proteins of the electron transport chain active in the light-dependent reactions ________.

A) are membrane proteins present in the thylakoid

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

33) The chemiosmotic process in chloroplasts involves the ________.

A) establishment of a proton gradient across the thylakoid membrane

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

47) Photorespiration ________.

A) generates carbon dioxide and consumes ATP and oxygen

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

49) Where do the enzymatic reactions of the Calvin cycle take place?

A) stroma of the chloroplast

10) Why are there several structurally different pigments in the reaction centers of photosystems?

B) This arrangement enables the plant to absorb light energy of a variety of wavelengths.

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?

B) B, C, D, and E

What would be the expected effect on plants if the atmospheric CO2 concentration was doubled?

B) C3 plants would have faster growth; C4 plants would be minimally affected.

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

B) H2O → NADPH → Calvin cycle

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?

B) NADPH

5) Which of the following statements best describes the relationship between photosynthesis and respiration?

B) Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules

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?

B) The bacteria would be relatively evenly distributed along the algal filaments.

43) How are the light-dependent and light-independent reactions of photosynthesis related?

B) The products of light-dependent reactions are used in light-independent reactions.

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?

B) They protect against oxidative damage from excessive light energy.

8) Chlorophylls absorb most light in which colors of the visible range?

B) blue and red

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?

B) blue and violet

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 ________.

B) carotenoids probably have a protective function in the cell

The process of photosynthesis probably originated ________.

B) in prokaryotes

40) In its mechanism, photophosphorylation is most similar to ________.

B) oxidative phosphorylation in cellular respiration

29) Which of the following are directly associated with photosystem I?

B) receiving electrons from the thylakoid membrane electron transport chain

When oxygen is released as a result of photosynthesis, it is a direct by-product of ________.

B) splitting water molecules

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 ________.

B) test for liberation of O2 in the lightB

51) Reactions that require CO2 take place in ________.

B) the Calvin cycle alone

22) What is the difference between NAD+ and NADP?

C) Both function as electron carriers, but NADP has a phosphate group and NAD+ does not.

54) The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?

C) Both minimize photorespiration but expend more ATP during carbon fixation.

23) As electrons are passed through the system of electron

C) It is used to establish and maintain a proton gradient.

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?

C) The CO2 acceptor concentration would increase when the CO2 is cut off but decrease when the light is cut off.

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?

C) a mixture of blue and red light

38) The accumulation of free oxygen in Earth's atmosphere began with the origin of ________.

C) cyanobacteria using photosystem II

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?

C) cyclic electron flow

16) Plants photosynthesize ________.

C) only in the light but respire in light and dark

6) In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during

C) photosynthesis and respiration

46) Which of the following procedures would identify the enzyme that catalyzes the carboxylation of ribulose-1,5-bisphosphate?

C) purifying a variety of proteins from plant extracts and testing each protein individually to see if it can carboxylate ribulose-1,5-bisphosphate

36) In mitochondria, chemiosmosis moves protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis moves protons from the ________.

C) stroma to the thylakoid space

26) What is the main purpose of light-dependent reactions of photosynthesis?

C) to produce NADPH and ATP

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?

C) water

13) What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?

D) An electron is excited.

9) Which of the following is a difference between chlorophyll a and chlorophyll b?

D) Chlorophyll a and b absorb light energy at slightly different wavelengths.

37) P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?

D) It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.

The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?

D) Other pigments absorb light in addition to chlorophyll a.

28) Which statement describes the functioning of photosystem II?

D) The electron vacancies in P680+ are filled by electrons derived from water.

52) The phylogenetic distribution of the enzyme rubisco is limited to ________.

D) bacterial and eukaryotic photoautotrophs

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 ________.

D) be higher in the light but lower in the dark

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 ________.

D) both lipid soluble and a molecule that serves as a shuttle between the electron transport chain and ATP synthase

41) Which process is most directly driven by light energy?

D) removal of electrons from chlorophyll molecules

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 ________.

D) synthesis of ATP

35) In a plant cell, where are the ATP synthase complexes located?

D) thylakoid membrane and inner mitochondrial membrane

3) Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

E) ATP and NADPH

27) Which of the events listed below occurs in the light reactions of photosynthesis?

E) Light is absorbed and funneled to reaction-center chlorophyll a.

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 ________.

E) O2

50) What is the primary function of the Calvin cycle?

E) synthesizing simple sugars from carbon dioxide