1. Suppose the stomata on a plant are covered with a substance that completely closes them. How w i l l this affect their ability to photosynthesize?

Answer: With the stomata covered, photosynthesis will slow down and eventually stop. This is because there is no way for the C02 to get into the leaf and into the cells to do the Calvin cycle. This means glucose can't be made and eventually the plant would die.

2. Chlorophyll is the primary pigment responsible for photosynthesis. During the autumn months, plants begin to produce less chlorophyll as they prepare to be dormant for the winter. How is a plant still able to survive during this time, i f it does not have as much chlorophyll available to it for photosynthesis?

Answer: There are other pigments (called accessory pigments, ex: carotenoids) that will also absorb light and will then donate their electrons to chlorophyll to still allow the processes to happen.

3. Both photosynthetic electron transport and the Calvin-Benson cycle stop when plants are placed in the dark. Which specific reaction stops first? Which stops next? Explain W H Y both pathways stop.

Answer: The light reactions stop first since there is no longer a source to excite the electrons. After this the Calvin Cycle will stop because the plant cell will run out of ATP and NADPH to power it

60. Yeast cells carry out both aerobic and anaerobic respiration. A yeast c d tfa* is fed on glucose is moved from an aerobic to an anaerobic environmenL Whictiaf the following statements is correct and gives the correct reason forii?

(A) The cell dies because it cannot make ATP. ^ ^ JB Jhe cell would need to consume glucose at a much greater rate because aerobic

respiration is much more efficient as compared with anaerobic respiratioiL (C) The cell would need to consume another food source other than ucose because

it will not be able to make adequate ATP with only glucose. (D) The ceil will begin to divide rapidly because larger cells require more oxjgen and

glucose than smaller ones.

Questions 61-62

Intact chloroplasts are isolated from dark-green leaves by low-speed centrifugation and are placed into six tubes containing cold buffer. A blue dye, DPIP, which nmis clear when reduced, is also added to all the tubes. Then each tube is exposed to different v%-avelengths of light. A measurement of the amount of decolorization is made, and the data are ploned on a graph. Although the wavelengths of light vary, the light intensity- is the same.

5 10 15 20 Time (in minutes)

61. Which statement below best describes the results of the experiment?

(A) The lower the wavelength of light, the greater the rate of photosynthesis. (B) The highest wavelengths of light provide the fastest rate of photosynthesis. (CT^The highest rate of photosynthesis results from exposure to two different

wavelengths of light. (D) The greatest reduction in DPIP occurs at 550 run light intensity.

400 AP BIOLOGY

62. What is the best explanation for the results in Questic

(A) 650 nm and 700 nm of light have the greatest pent (B) The photosynthetic pigments in the experiment dc

650 nm and 700 nm range. (O Only wavelengths of 650 nm and 700 nm are reflect.

/ fDFThe chloroplasts have two photosystems that absorb ''^^__..-^avelengths.

42. The graph on the left (A) shows an absorption spectrum for chlorophyll a extracted from a plant. The graph on the right (E) shows an action spectnun from a living plant, with wave lengths of light plotted against the rate of photosynthesis as measured by release of oxygen.

400 500 600 700 Violet Green Orange Red

Wavelength (nm)

400 500 600 700 Violet Green Orartge Red

Wavelength (nm)

(A) <B)

Which statement best explains the difference between the two spectra?

(A) Graph A plots the absorption spectrum of a red plant; graph B plots an ^...-^absorption spectrum for a green plant. (B) yThe chlorophyll from Graph A carmot carry out the light-dependent reactions;

but the chlorophyll in graph B can. (C) The data from Graph A characterize several photosynthetic pigments that reflect

almost no light; the data from Graph B characterize chlorophyll a, which reflects only green light.

(D) Graph A shows an absorption spectrum for an unusual type of chlorophyll a.

I.

•3 Questions 60-63

The diagram below shows energy transformations within a cell. Each form of energy is represented by the symbols E I-E IV. Two cellular organelles are represented by the letters A and B. Answer the following questions about the various processes depicted in the diagram and about the cell in which they are occurring.

Organelle A HjO sp rt CO. fixed- Etll

COrganelle B \ C,H,,0, - E IV )

PART FOUR: PRACTICE TESTS PRACTICE TEST 1 247

61. If the transformation depiaed in oi^anelle [^requires oxygen^hat form of energy is represented

(A) Radiant energy in the form of photons (B) Chemical energy being stored as glycogen

^ Cp Chemical energy in the form of ATP (D) Chemical energy released by glycolysis

62. What cellular organelles are represented as A and B, respectively?

(A) The nucleus and the ribosome (B) The mitochondrion and the chloroplast (C) The mitochondrion and the ribosome

^^^ ) ^ lie chloroplast and the mitochondrion

63. Which kind of organism could the cell shown belong to? ^ cWV«n>P \ \

(A) A photosynthetic bacteria ^)_AphotosyntheticprotJiT^ c p K ^ ^ « v - ^ » ' ^

60. What form of energy is represented by E II?

(A) Radiant energy in the form of photons (B) Chemical energy being stored in the bonds

of glucose ^^(Q^^HemicaJ energy in the form of ATP

(D) Qiemical energy released by glycolysis

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PART FOUR: PRACTICE TESTS PRACTICE TEST 2

18. When ATP is used for transport, mechanical, or chemical work,

(A) it is the adenosine that performs the work.

( j B ) 3 i t is the phosphoryiates that perform the work. ^ rtd^ PDH (pUoyiu-k-jyij;*.p)

(C) it is the precursor, ADP, that performs the work.

(D) it is the energy released when ATP leaves the mitochondria that performs the work.

26. During complete aerobic cellular respiradon, each molecule of glucose broken down in the mitochondria can yield 36 molecules of ATP What conditions might lead to a decrease in the amount of ATP produced in a given system?

(A) An increase in the amount of glucose added to the system

(B) A decrease in the amount of light the system is exposed to

(C) A decrease in the amount of oTy^n available in the s^em

(D) A decrease in the amount of carbon dioxide available in the system

27. During photosynthesis

(A) light reactions produce sugar, while the Ivin cycle prodiK''^ O2

(B) light reactions produce NADPH anc ATP, while the Calvin cycle produces

(C) light reactions photophosphorylate ADP, while the Calvin cycle produces ATP.

(D) the Calvin cycle produces both sugar and

When NAD"^ is reduced to N A D H by dehydrogenase, what is released into the surrounding solution?

(A) An electron (B) Hydrogenase ( O A protonj) CD) Hydrogen

21. What is the function of the electron transpon chain in cellularrespiration?

f i^^To break a large free-energy drop into smaller energy-releasing steps

(B) To make ATP m 1 o ^ ^'J)

(C) To store electrons for use in the Krebs cycle

(D) To convert pyruvate to acetyl CoA

37. What source of energy does ATP synthase use to generate ATP from ADP and inorganic phosphate in cellular respiration?

(A) Light energy (B) Fermentation

(D) Enzymes J

38. Cellular respiration produces much more ATP per glucose molecule than fermentation because

(A) respiration uses glycolysis to oxidize glucose.

(B) oxygen is necessary to release energy jtored in pyruvate^___-.

(C) fermentation uses NAD"^ as the ^idizing agem in glycolysis.

(D) respiration produces 2 ATP via glycolysis.

44, The tradeoff between water loss and COj uptake has resulted in the evolution of what adaptation in many plants that experience a hot, dry environment?

di^C4 and CAM photosyntl^) (B) C3 and CAM photosynthesis (C) C3 and C4 photosynthesis (D) Photorespiration that generates ATP

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ment representing

, tell respiri'tion

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pro.' •• >••

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« Strom*~*ite of iighHnde,v.Klon. „f n en.branes called

(hvlaKoids „ j„ production of glucose I) Innrr plasma membrane—does nor take P v,,,.,nnla.!s bv

„i the grana of chloroplasts by Light harvested in the lh^ takoid nienit>r ^ ^^^.^^ . njer containing the phoios\-stems. Vjxch phniosysteni '"""^'^Y^everal luindred other photosynthetic phoiosyiuhetk-pigment chlorophyll« a"* t-hlorophyli «. There are two antenna pigments that ftinnel hghi ^^^ ^ ^ ^^ ,j ^bsorbs light in phoios>sUMiis (ra. rs I absorbs light .n * spectrum the^X>n.r.nge.rhe..eonhe.nte^^^ of ligh. absorbed by d»loroph>1l a. Ught is • ^ ^ chlorophvll excites eiectro.is v-ithin the moie.nte me e excu . • .i,..r «'in iilrinaioiv iransfer the energy cMpiLirod bv .m eleanui tran*;port chain thdl will ui i irnn . i -n BJ

TO ;VrP

When excited electmas from chioruph)4luare captured by a n electron transport dain in the th>iakoid membrane, ihey enter at a high energ>' level and then drop down 10 succesmTly lower energN- le -els, releasing encrg>- as they fall. The energy released from this exergohio flow of electrons is coupled with an endergonic reaction and used to pump pmio^ H- thylakoid membrane. This process creatt- a proton gradient w .he inyiakoid space (lumen). The thylakoid membrane is impemieable to protons except at ATP synthase structures. As protons flow down the gradient and through the ATP synthase molecules, ADP is phosphoryliited irao ATP. This pn;. .'- similar to what happens in oxidative phospl - during cellular respiration. However, because the movement of _i _ . • ^ powered by solar energy, thi; process is called photophosphorytation. Finath', N. DPH and E\DH, carry spent protons and elecn^ns from the light-dependent reactions to the Cahin cycle.

The business of the light-independent reactions is to f k carbon into a molecule of st.gar--PGAL. also k n o H . . as 3-PG.%. The CaJvm cycle is the process by which

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4S2 AP RIOLOGY