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6
ENERGY
FOR
LIFE
CHAPTER REVIEW
The topic of this chapter is photosynthesis, the process
that produces enough food to directly or indirectly feed
the world. Photosynthesis begins with light reactions,
which occur in thylakoids of chloroplasts and produce
NADPH and ATP. NADPH and ATP are used by the
Calvin cycle reactions to reduce carbon dioxide to a
carbohydrate. C 3 photosynthesis, named for the first
detected molecule, has been studied for many years,
but now we know that many plants carry out C 4 photosynthesis. The first detected molecule during the
process of C 4 photosynthesis is a C 4 molecule.
CHAPTER KEY TERMS
After studying the key terms of this chapter, match the phrases below with the alphabetized list of terms.
ATP synthase
electron transport chain
C 3 plant
grana
C 4 plant
light reactions
Calvin cycle reactions
RuBP carboxylase (rubisco)
carotenoid
stomata
chlorophyll
stroma
chloroplast
thylakoid
a. first series of reactions during photosynthesis _______________________
b. second series of reactions during photosynthesis _______________________
c. green in color; captures solar energy _______________________
d. orange in color; captures solar energy _______________________
e. passage of electrons; releases energy _______________________
f. organelle where photosynthesis occurs _______________________
g. enzyme that produces ATP _______________________
h. membranous sac; part of grana, where the light reactions occur _______________________
i. plant of temperate zone that uses Calvin cycle directly _______________________
j. plant that tolerates hot, dry climate and uses Calvin cycle indirectly _______________________
k. fluid within chloroplast where Calvin cycle reactions occur _______________________
l. stack of thylakoids_______________________
m. small openings in leaf for gas exchange _______________________
n. first enzyme of the Calvin cycle, fixes CO 2 _______________________
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S T U DY E X E R C I S E S
Study the text section by section as you answer the questions that follow.
6.1 OVERVIEW
OF
PHOTOSYNTHESIS (PP. 84–86)
• Plants, algae, and cyanobacteria are photosynthetic organisms that produce most of the carbohydrates used for
energy by the living world.
• In flowering plants, photosynthesis takes place within chloroplasts, organelles that contain membranous
thylakoids surrounded by a fluid called stroma.
• Photosynthesis has two sets of reactions: Pigments in the thylakoids capture solar energy, and enzymes in the
stroma reduce carbon dioxide.
1. After studying the following diagram, answer the questions:
Solar
energy
Leaf cross section
leaf vein
CO2
O2
stoma
chloroplast
stroma
a. Why is solar energy in this diagram?
grana
_____________________________________________________________
b. Why is the leaf in this diagram? __________________________________________________________________
c. Why is the chloroplast in this diagram? ___________________________________________________________
d. An overall equation for photosynthesis is CO 2 + H 2 O
(CH 2 O) + O 2 . How does carbon dioxide enter and
oxygen leave a leaf? ____________________________________________________________________________
e. How does water enter a leaf? ____________________________________________________________________
f. What pigment captures solar energy? _____________________________________________________________
g. Where is this pigment located? ___________________________________________________________________
2. Place the appropriate letters next to each phrase:
LR—light reactions
CC—Calvin cycle reactions
a.
CO 2 enters these reactions.
b.
Chlorophyll absorbs solar energy.
c.
ATP and NADPH are produced.
d.
ATP and NADPH are used to produce a carbohydrate.
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6.2 LIGHT REACTIONS (PP. 87–89)
• Plants use solar energy in the visible light range when they carry on photosynthesis.
• Solar energy energizes electrons and permits a buildup of ATP and NADPH molecules.
3. After studying the following diagram of the light reactions, answer the questions:
electron
acceptor
NADP+
e–
e–
H+
electron
acceptor
NADPH
ctr
on
ns
e–
rgy
tra
ene
Ele
s olar
e–
po
rt c
reaction center
ha
in
ADP + P
PS I
s olar
ene
e–
rgy
reaction center
ATP
Energy Level Increases
pigment
complex
PS II
e–
water splits H 2O
1
–
2
2 H+
O2
a. Both photosystem II (PSII) and photosystem I (PSI) do what?
b. What else does PSII do?
_______________________________________
________________________________________________________________________
c. What else does PSI do? _________________________________________________________________________
d. What does the electron transport chain do? ________________________________________________________
e. What two molecules are produced by the light reactions and sent to the Calvin cycle reactions? __________
4. Answer the following questions to explain ATP production:
a. Where in a thylakoid would you find the complexes that carry on the light reactions? ___________________
b. Hydrogen ions (H ) are pumped into what part of a thylakoid? _______________________________________
c. What happens to the hydrogen ions (H )? _____________________________________________________
______________________________________________________________________________________________
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6.3 CALVIN CYCLE REACTIONS (PP. 90–91)
• Carbon dioxide reduction requires ATP and NADPH from the light reactions.
5. Match the numbers in the diagram to the following descriptions of events in the Calvin cycle (some numbers
are used more than once):
2 3PG
a.
fixation of carbon dioxide
b.
reduction of carbon dioxide
C6
c.
regeneration of RuBP
1.
d.
RuBP
2.
e.
NADPH and ATP required to reduce CO 2
RuBP
f.
two molecules produce glucose
3.
G3P
G3P
other organic
molecules
4.
glucose phosphate
6. Why are plants more biochemically competent than animals?
6.4 OTHER TYPES
OF
PHOTOSYNTHESIS (PP. 92–93)
• Plants use C 3 , C 4 , or CAM photosynthesis, which are distinguishable by the manner in which CO 2 is fixed.
7. Place the appropriate letters next to each phrase.
C 3 —C 3 plant
C 4 —C 4 plant
CAM—CAM photosynthesis
a.
A cross section of this plant is shown in diagram for question 1, p. 47. This plant carries out the
Calvin cycle directly and the first molecule detected is 3PG, a three-carbon molecule.
b.
In this plant, the cells of the leaf are circularly arranged around the leaf vein. CO 2 is fixed
in the outer ring of cells and then sent to the inner ring of cells, where the Calvin cycle reactions
occur. The molecule that results from CO 2 fixation is a C 4 molecule.
c.
Stomata open at night and CO 2 is fixed at night.
8. What’s the advantage of C 4 photosynthesis and CAM photosynthesis?
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K E Y WO R D C RO S S WO R D
Review key terms by completing this crossword puzzle using the following alphabetized list of terms:
1
2
3
4
5
6
C 3 plant
C 4 plant
Calvin cycle
CAM plant
chlorophyll
granum
light reaction
photosystem
RuBP
stomata
stroma
thylakoid
7
8
9
Across
2 plant that directly uses the Calvin cycle; the first detected molecule during photosynthesis is 3PG, a
three-carbon molecule (two words)
4 green pigment that absorbs solar energy and is important in photosynthesis
7 stack of chlorophyll-containing thylakoids in a
chloroplast
8 flattened sac within a granum whose membrane
contains the photosynthetic pigments (e.g., chlorophyll); where the light reactions occur
9 small openings in leaves through which carbon
dioxide enters
50
Down
1 plant that fixes carbon dioxide at night to produce
a C4 molecule that releases carbon dioxide to the Calvin
cycle during the day (two words)
2 plant that fixes carbon dioxide in bundle sheath
cells to produce a molecule that releases carbon
dioxide to the Calvin cycle in mesophyll (two words)
3 set of photosynthetic reactions that requires solar
energy to proceed; it produces ATP and NADPH
(two words)
4 uses the products of the light reactions to reduce
carbon dioxide to a carbohydrate (two words)
5 five-carbon compound that combines with and fixes
carbon dioxide during the Calvin cycle and is later
regenerated by the same cycle
6 photosynthetic unit where solar energy is absorbed;
contains an antenna (photosynthetic pigments) and
an electron acceptor
9 large, central space in a chloroplast that is fluid filled
and contains enzymes used in photosynthesis
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CHAPTER TEST
OBJECTIVE QUESTIONS
Do not refer to the text when taking this test. In questions 1–6, match the definitions to these terms.
a. chlorophyll
b. oxygen
c. stroma
d. sugar
e. thylakoid membrane
f. water
1.
2.
3.
4.
5.
6.
organic product of photosynthesis
released by photosynthesis
reactant of photosynthesis
site of light reactions
site of Calvin cycle reactions
molecule absorbing solar energy
7. Which one of these does not occur during the
light reactions?
a. H buildup in thylakoid space
b. NADPH production
c. G3P production occurs.
d. Water is split.
e. All of these occur during the light reactions.
8. Which of these statements properly describes
how CO 2 enters a leaf?
a. CO 2 is carried by water in leaf veins.
b. CO 2 is not needed by photosynthesis.
c. CO 2 is pulled in by leaf cells.
d. CO 2 diffuses in by way of the stomata.
9. Each of the following is a product of photosynthesis EXCEPT
a. carbon dioxide.
b. organic food.
c. oxygen.
d. carbohydrate.
10. Each is a product of light reactions EXCEPT
a. ATP.
b. NADPH.
c. oxygen.
d. sugar.
11. The cyclic pathways of photosynthesis produce
a. ATP only.
b. NADPH only.
c. ATP and NADPH.
d. organic sugars only.
12. Carbon dioxide fixation occurs when CO 2 combines with
a. ATP.
b. NADPH.
c. G3P.
d. RuBP.
13. The enzyme that produces ATP from ADP + P
in the thylakoid is
a. RuBP carboxylase.
b. G3P.
c. ATPase.
d. ATP synthase.
e. coenzyme A.
14. Which of the following is NOT a stage in the
Calvin cycle?
a. carbon dioxide fixation
b. carbon dioxide oxidation
c. carbon dioxide reduction
d. RuBP regeneration
15. Which of these descriptions is NOT true of
photosynthesis?
a. not affected by temperature
b. not affected by solar energy
c. requires a supply of oxygen
d. involves a reduction reaction
e. more likely to occur during the day
16. Which of these descriptions is NOT true of
chlorophyll?
a. absorbs solar energy
b. located in the grana
c. located in thylakoid membranes
d. passes electrons directly to NADP +
e. passes electrons to an acceptor molecule
17. The two major sets of reactions involved in photosynthesis are
a. the cyclic and noncyclic electron pathways.
b. glycolysis and the citric acid cycle.
c. the Calvin and citric acid cycles.
d. the Calvin cycle and the electron transport
chain.
e. the light reaction and the Calvin cycle
reaction.
18. Which of the following statements is NOT true
of the Calvin cycle?
a. RuBP is regenerated with the use of ATP.
b. Glucose phosphate is synthesized from G3P.
c. NADPH is used to reduce G3P to 3PG.
d. Five molecules of G3P are used to reform
three molecules of RuBP.
19. Photosystem II gets replacement electrons from
a. the sun.
b. water molecules.
c. ATP.
d. photosystem I.
e. NADPH.
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CRITICAL THINKING QUESTIONS
The introduction to this chapter is about photosynthesis and you.
20. What does photosynthesis do for you? ______________________________________________________________________
21. What else does photosynthesis do for you? __________________________________________________________________
22. Where does the CO 2 taken in by plants come from? __________________________________________________________
23. Where do plants get their energy to produce food? ___________________________________________________________
24. Why is photosynthesis necessary to our lives and the lives of all living things? _______________________________
Test Results: ______ number correct ÷ 24 = ______ × 100 = ______ %
EXPLORING
THE
INTERNET
ARIS, the Essentials of Biology website: http://www.mhhe.com/maderessentials
ARIS, the website for Essentials of Biology, offers access to a wide variety of tools to help students learn biological
concepts and to reinforce their knowledge. Online study aids such as practice quizzes, interactive activities, animations, labeling exercises, flashcards, and much more are organized according to the major sections of each chapter.
There is even an online tutorial service!
ANSWER KEY
CHAPTER KEY TERMS
a. light reactions b. Calvin cycle reactions c. chlorophyll d. carotenoid e. electron transport chain f. chloroplast g. ATP synthase h. thylakoid i. C 3 plant
j. C 4 plant k. stroma l. grana m. stomata n. RuBP carboxylase (rubisco)
KEYWORD CROSSWORD
1
C
2
C
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4
M
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P
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3
L
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4
G
5
C H
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A
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STUDY EXERCISES
3
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P H
52
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6
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1. a. Solar energy drives photosynthesis. b. Leaves are
the organs of photosynthesis. c. Photosynthesis occurs
in chloroplasts. d. through stomata e. leaf vein f. chlorophyll g. grana 2. a. CC b. LR c. LR d. CC 3. a. capture solar energy b. splits water releasing O 2 c. pass
electrons to NADP so that NADPH results d. leads to
ATP production e. NADPH and ATP 4. a. thylakoid
membrane b. thylakoid space c. They cross the thylakoid
membrane through the ATP synthase complex and trigger the production of ATP. 5. a. 1 b. 2 c. 3 d. 3
e. 2 f. 4 6. They produce every molecule their bodies
need, including their own organic nutrients. 7. a. C 3
b. C 4 c. CAM 8. In a hot dry climate, C 4 photosynthesis and CAM photosynthesis can continue at full speed,
but C 3 photosynthesis slows down because rubisco has
combined with oxygen, a by-product of photosynthesis.
Y
T
7
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U M
H
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A
CHAPTER TEST
1. d 2. b 3. f 4. e 5. c 6. a 7. c 8. d 9. a
10. d 11. a 12. d 13. d 14. b 15. c 16. d
17. e 18. d 19. b 20. produces food 21. produces
O2 22. The CO2 is given off by us and all organisms that
carry out cellular respiration. 23. the sun 24. produces organic nutrients and oxygen