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AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 1 -

Name_______________________Period___________

Chapter 10: Photosynthesis

This chapter is as challenging as the one you just finished on cellular respiration. However,

conceptually it will be a little easier because the concepts learned in Chapter 9—namely,

chemiosmosis and an electron transport system—will play a central role in photosynthesis.

1. As a review, define the terms autotroph and heterotroph. Keep in mind that plants have

mitochondria and chloroplasts and do both cellular respiration and photosynthesis!

Concept 10.1 Photosynthesis converts light energy to the chemical energy of food

2. Take a moment to place the chloroplast in the leaf by working through Figure 10.3. Draw a

picture of the chloroplast and label the stroma, thylakoid, thylakoid space, inner membrane,

and outer membrane.

3. Use both chemical symbols and words to write out the formula for photosynthesis (use the one

that indicates only the net consumption of water). The formula is the opposite of cellular

respiration. You should know both formulas from memory.

4. Using

18

O as the basis of your discussion, explain how we know that the oxygen released in

photosynthesis comes from water.

5. Photosynthesis is not a single process, but two processes, each with multiple steps.

a. Explain what occurs in the light reactions stage of photosynthesis. Be sure to use NADP

+

and photophosphorylation in your discussion.

b. Explain the Calvin cycle, utilizing the term carbon fixation in your discussion. AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 2 -

6. The details of photosynthesis will be easier to organize if you can visualize the overall process.

Label Figure 10.5, below. As you work on this, underline the items that are cycled

between the light reactions and the Calvin cycle.

Concept 10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH

This is a long and challenging concept. Take your time, work through the questions, and realize that

this is the key concept for photosynthesis.

7. Some of the types of energy in the electromagnetic spectrum will be familiar, such as X-rays,

microwaves, and radio waves. The most imporant part of the spectrum in photosynthesis is

visible light. What are the colors of the visible spectrum?

Notice the colors and corresponding wavelengths and then explain the relationship between

wavelength and energy.

8. Read Figure 10.9 carefully; then explain the correlation between an absorbtion spectra and an

action spectrum.

9. Describe how Englemann was able to form an action spectrum long before the invention of a

spectrophotometer. AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 3 -

10. A photosystem is composed of a protein complex called a ___________-__________ complex

surrounded by several __________-____________ complexes.

11. Within the photosystems, the critical conversion of solar energy to chemical energy

occurs. This process is the essence of being a producer! Using Figure 10.12 as a guide, label the

diagram and then explain the role of the terms in the photosystem.

a) Reaction center complex—

b) Light-harvesting complex—

c) Primary electron acceptor—

12. Photosystem I is referred to by the wavelength at which its reaction center best absorbs light, or

P__________; photosystem II is also known by this characteristic, or P__________. AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 4 -

13. Linear electron flow is, fortunately, easier than it looks. It is an electron transport chain,

somewhat like the one we worked through in cellular respiration. While reading the section

“Linear Electron Flow,” label the diagram number by number as you read.

14. The following set of questions deal with linear electron flow:

a. What is the source of energy that requires the electron in photosystem II?

b. What compound is the source of electrons for linear electron flow? This compound is also

the source of ___________ in the atmosphere.

c. As electrons fall between photosystem I and II, the cytochrome complex uses the energy to

pump ________ ions. This builds a proton gradient that is used in chemiosmosis to produce

what? AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 5 -

d. In photosystem II, the excited electron is eventually used by NADP

+

reductase to join

NADP

+

and a H

+

to form ___________.

* Notice that two high-energy compounds have been produced by the light reactions: ATP and

NADPH. Both of these compounds will be used in the Calvin cycle.

15. Cyclic electron flow can be visualized in Figure 10.15. Cyclic electron flow is thought to be

similar to the first forms of photosynthesis to evolve. In cyclic electron flow no water is split,

there is no production of __________, and there is no release of __________.

16. The last idea in this challenging concept is how chemiosmosis works in photosynthesis. Use

four examples to compare how chemiosmosis is similar in photosynthesis and cellular

respiration.

17. Use two key differences to explain how chemiosmosis is different in photosynthesis and

cellular respiration. (These two questions are another example of compare and contrast.)

18. Label all the locations in the diagram first. Next, follow the steps in linear electron flow to label

the components of the light reactions in chemiosmosis. AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 6 -

19. List the three places in the light reactions where a proton-motive force is generated.

20. As a review, note that the light reactions store chemical energy in __________ and

__________, which shuttle the energy to the carbohydrate-producing __________ cycle.

Concept 10.3 The Calvin cycle uses ATP and NADPH to convert CO2 to sugar

The Calvin cycle is a metabolic pathway in which each step is governed by an enzyme, much like the

citric acid cycle from cellular respiration. However, keep in mind that the Calvin cycle uses energy (in

the form of ATP and NADPH) and is therefore anabolic; in contrast, cellular respiration is catabolic

and releases energy that is used to generate ATP and NADH.

21. The carbohydrate produced directly from the Calvin cycle is not glucose, but the three-carbon

compound __________________________. Each turn of the Calvin cycle fixes one molecule

of CO2; therefore, it will take ___________ turns of the Calvin cycle to net one G3P.

22. Explain the important events that occur in the carbon fixation stage of the Calvin cycle.

23. The enzyme responsible for carbon fixation in the Calvin cycle, and possibly the most abundant

protein on Earth, is __________________.

24. In phase two, the reduction stage, the reducing power of _________________ will donate

electrons to the low-energy acid 1,3-bisphosphoglycerate to form the three-carbon sugar

._________________________ AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 7 -

25. Examine Figure 10.18 while we tally carbons. This figure is designed to show the production of

one net G3P. That means the Calvin cycle must be turned three times. Each turn will require a

starting molecule of ribulose bisphosphate, a five-carbon compound. This means we start with

__________ carbons distributed in three RuBPs. After fixing three carbon dioxides using the

enzyme _______________, the Calvin cycle forms six G3Ps with a total of _________

carbons. At this point the net gain of carbons is _________, or one net G3P molecule.

26. Three turns of the Calvin cycle nets one G3P because the other five must be recycled to RuBP.

Explain how the regeneration of RuBP is accomplished.

27. The net production of one G3P requires __________ molecules of ATP and __________

molecules of NADPH.

Concept 10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates

28. Explain what is meant by a C3 plant.

29. What happens when a plant undergoes photorespiration?

30. Explain how photorespiration can be a problem in agriculture.

31. Explain what is meant by a C4 plant. AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 8 -

32. Explain the role of PEP carboxylase in C4 plants, including key differences between it and

rubisco.

33. Conceptually, it is important to know that the C4 pathway does not replace the Calvin cycle but

works as a CO2 pump that prefaces the Calvin cycle. Explain how changes in leaf architecture

help isolate rubisco in high CO2 areas but low O2 areas.

34. Using Figure 10.19 as a guide, explain the three key events—indicated by the arrows below—

in the C4 pathway. AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 9 -

35. Compare and contrast C4 plants with CAM plants. In your explanation, give two key

similarities and two key differences.

36. Explain the statement that only the green cells of a plant are the autotroph while the rest of the

plant is a heterotroph.

37. Now that you have worked through the entire chapter, study Figure 10.21. Go back to the figure

used in question 6. On the left side of that figure, list additional information for the light reactions;

on the right side, summarize additional information for the Calvin cycle reactions. Finally, label

this entire figure without looking back in your book! If you can do this, you understand the “big

picture.” AP Biology Reading Guide Chapter 10: Photosynthesis

Fred and Theresa Holtzclaw

Copyright © 2010 Pearson Education, Inc. - 10 -

Testing Your Knowledge: Self-Quiz Answers

Now you should be ready to test your knowledge. Place your answers here:

1.________ 2.________ 3._________ 4.________ 5._________ 6._________ 7._________

[pic]
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|1.   |Plants are photoautotrophs. What does this mean? (p. 176) | |[pic] | | | | | | |[pic]They make their own food from inorganic materials. | | |[pic]They are among the producers of the biosphere. | | |[pic]They are in the same category as algae and cyanobacteria. | | |[pic]They use light energy to drive the synthesis of organic molecules. | | |[pic]All of the above. | | | | | |[pic] | |2.   |The ultimate source of energy to support most life on Earth is _____. (p. 176) | |[pic] | | | | | | |[pic]photosynthetic plants | | |[pic]chemosynthetic microbes | | |[pic]geothermal heat | | |[pic]the carbon cycle | | |[pic]sunlight | | | | | |[pic] | |3.   |The photosynthetic membranes are found in the __________ in plant cells. (p. 178) | |[pic] | | | | | | |[pic]Golgi apparatus | | |[pic]endoplasmic reticulum | | |[pic]mitochondria | | |[pic]chloroplasts | | |[pic]nucleus | | | | | |[pic] | |4.   |When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____. (p. 186) | |[pic] | | | | | | |[pic]splitting water | | |[pic]breaking down ATP | | |[pic]removing them from NADPH | | |[pic]fixing carbon | | |[pic]oxidizing glucose | | | | | |[pic] | |5.   |Photosynthesis is an __________ process of carbon __________, while respiration is an __________ process of carbon | |[pic] |__________. (p. 190) | | | | | |[pic]endergonic ... reduction ... exergonic ... oxidation | | |[pic]endergonic ... oxidation ... endergonic ... reduction | | |[pic]exergonic ... reduction ... endergonic ... oxidation | | |[pic]endergonic ... oxidation ... exergonic ... reduction | | |[pic]exothermic ... oxidation ... endothermic .... reduction | | | | | |[pic] | |6.   |Which of the following is produced by the light reactions of photosynthesis and consumed by the Calvin cycle? (p. 185) | |[pic] | | | | | | |[pic]NADPH | | |[pic]oxygen | | |[pic]water | | |[pic]sugar | | |[pic]ADP + Pi | | | | | |[pic] | |7.   |In the electromagnetic spectrum, the type of radiation that we call visible light occurs between ___________. (p. 181) | |[pic] | | | | | | |[pic]radio waves and microwaves | | |[pic]infrared radiation and microwaves | | |[pic]infrared radiation and radio waves | | |[pic]X-rays and ultraviolet radiation | | |[pic]ultraviolet radiation and infrared radiation | | | | | |[pic] | |8.   |Which of the following is NOT a product of the light reactions of photosynthesis? (p. 185) | |[pic] | | | | | | |[pic]oxygen | | |[pic]sugar | | |[pic]high-energy electrons | | |[pic]ATP | | |[pic]NADPH | | | | | |[pic] | |9.   |The overall function of the Calvin cycle is _____. (p. 189) | |[pic] | | | | | | |[pic]capturing sunlight | | |[pic]making sugar | | |[pic]producing carbon dioxide | | |[pic]splitting water | | |[pic]oxidizing glucose | | | | | |[pic] | |10.   |C4 plants occur more commonly in desert conditions because _____. (p. 192) | |[pic] | | | | | | |[pic]they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed | | |[pic]they produce water as a product of their photosynthetic pathways | | |[pic]they produce carbon dioxide internally via photorespiration | | |[pic]the stomata open at night and close in the day | | |[pic]they store carbon by incorporating CO2 into organic acids that are later catabolized |

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