Download Photosynthesis reading review

Name _______________________________Class __________________ Date __________________
CHAPTER 6 ACTIVE READING PHOTOSYNTHESIS
Section 6-1: The Light Reactions
Read the passage below, which covers topics from your textbook. Answer the questions that follow.
1
Located in the membrane of the thylakoids are a variety of pigments, the most important of which are
called chlorophylls.
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3
There are several different types of chlorophylls. The two most common types are known as
chlorophyll a and chlorophyll b.
4 A slight difference in molecular structure between chlorophyll a and chlorophyll b causes the two
molecules to absorb different colors of light. 5 Chlorophyll a absorbs less blue light but more red light than
chlorophyll b absorbs. 6 Neither chlorophyll a nor chlorophyll b absorbs much green light. 7 Instead, they
allow green light to be reflected or transmitted. 8 That is why leaves and other plant structures that contain
large amounts of chlorophyll look green. 9 Only chlorophyll a is directly involved in the light reactions of
photosynthesis. 1 0 Chlorophyll b assists chlorophyll a in capturing light energy; therefore, chlorophyll b is
called an accessory pigment.
SKILL: Identifying Main Ideas. Read each question and write your answer in the space provided.
1. Which sentence identifies the main idea of the first paragraph?
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2. What supporting details are described by the remaining sentences in the first paragraph?
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SKILL: Recognizing Similarities and Differences.
One reading skill is the ability to recognize similarities and differences between two phrases, ideas, or
things. This skill is sometimes known as comparing and contrasting. Some clue words that writers use
when pointing out similarities or making comparisons are like, as, similarly, similar to, neither, nor, and in
the same way. Some clue words that writers use when pointing out differences or making contrasts include
however, but, although, on the contrary, still, either, or, and on the other hand.
3. What difference between chlorophyll a and chlorophyll b is noted in Sentence 4?
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4. Does Sentence 5 note a similarity or a difference between these molecules?
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5. What is the similarity or difference noted in Sentence 5?
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6. Does Sentence 6 note a similarity or a difference?
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7. What is the similarity or difference noted in Sentence 6?
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SKILL: Recognizing Cause-and-Effect Relationships
In a cause-and-effect relationship, one event, or cause, triggers a second event, or effect, to occur.
Determine the cause or effect in the question below.
8. What is the effect of the difference between chlorophyll a and chlorophyll b?
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Circle the letter of the phrase that best completes the statement.
9. Because chlorophyll b assists chlorophyll a in capturing light energy, chlorophyll b
a. is a carotenoid.
b. is called an accessory pigment.
c. absorbs more blue light than chlorophyll a.
d. reflects green light.
Section 6-2: The Calvin Cycle
Read the passage below, which covers topics from your textbook. Answer the questions that follow.
The Calvin cycle has four major steps that occur within the stroma of the chloroplasts.
Step 1. CO2 diffuses into the stroma from the surrounding cytosol. An enzyme combines each CO2
molecule with a five-carbon carbohydrate called RuBP. The product is a six-carbon molecule that splits
immediately into a pair of three-carbon molecules known as 3-PGA.
Step 2. Each molecule of 3-PGA is converted into another three-carbon molecule, G3P, in a two-part
process. First, each 3-PGA molecule receives a phosphate group from a molecule of ATP. The resulting
compound then receives a proton from NADPH and releases a phosphate group, producing G3P. In
addition to G3P, these reactions produce ADP, NADP+ , and phosphate. These three products can be used
again in the light reactions to synthesize additional molecules of ATP and NADPH.
Step 3. One molecule of G3P is used to make organic compounds.
Step 4. Most of the G3P is converted back into RuBP in a complicated series of reactions. These reactions
require a phosphate group from another molecule of ATP, which is changed into ADP. By regenerating the
RuBP that was consumed in Step 1, the reactions of Step 4 allow the Calvin cycle to continue operating.
Name _______________________________Class __________________ Date __________________
SKILL: Identifying Main Ideas
1. Summarize the main events that occur in each step of the Calvin cycle on the lines provided.
a. Step 1
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b. Step 2
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c. Step 3
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d. Step 4
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SKILL: Vocabulary Development
2. The prefix cyto- means “cell.” The suffix -logy means “study.” How does knowledge of these word
parts help define cytology?
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Circle the letter of the phrase that best completes the sentence.
3. If the RuBP consumed in Step 1 was not regenerated in Step 4 of the Calvin cycle, then
a. CO2 would stop diffusing into the stroma.
b. the cycle would speed up because of an increase in CO2 molecules.
c. the plant cell would lack G3P molecules.
d. the plant cell would stop bonding carbon atoms from CO2 into organic compounds.
Name _______________________________Class __________________ Date __________________
SECTION 6-1 REVIEW THE LIGHT REACTIONS
VOCABULARY REVIEW Explain the relationship between the terms in each of the following pairs.
1. granum, stroma ____________________________________________________
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2. chlorophyll a, carotenoids ____________________________________________
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3. chemiosmosis, ATP synthase __________________________________________
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MULTIPLE CHOICE Write the correct letter in the blank.
______ 1. Chlorophyll a
a. absorbs mostly orange-red and blue-violet light.
b. absorbs mostly green light.
c. is an accessory pigment.
d. is responsible for the red color of leaves.
______ 2. The photosystems and electron transport chains are located in the
a. outer chloroplast membrane.
c. thylakoid membrane.
b. inner chloroplast membrane.
d. stroma.
______ 3. Both photosystem I and photosystem II
a. receive electrons from other photosystems.
b. donate electrons to a transport chain that generates NADPH
c. donate protons to each other.
d. contain chlorophyll a molecules.
______ 4. Water participates directly in the light reactions of photosynthesis by
a. donating electrons to NADPH.
c. accepting electrons from the electron transport chains.
b.donating electrons to photosystem II. d. accepting electrons from ADP.
______ 5. The energy used to establish the proton gradient across the thylakoid membrane comes from the
a. synthesis of ATP.
b. synthesis of NADPH.
c. passage of electrons along the electron transport chain of photosystem II.
d. splitting of water.
SHORT ANSWER Answer the questions in the space provided.
1. Why is photosynthesis referred to as a biochemical pathway? ________________
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2. How does the structure of a chloroplast enable it to build up a concentration gradient of protons?
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3. What are the energy-carrying end products of the light harvesting reactions?
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4. Explain the function of accessory pigments. ______________________________
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5. Critical Thinking Which photosystem—I or II—most likely evolved first? Explain your reasoning.
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STRUCTURES AND FUNCTIONS Label the substances represented by the letters a–d below.
The diagram below summarizes the light reactions of photosynthesis.
Name _______________________________Class __________________ Date __________________
SECTION 6-2 REVIEW THE CALVIN CYCLE
VOCABULARY REVIEW Define the following terms.
1. Calvin cycle _______________________________________________________
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2. carbon fixation _____________________________________________________
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3. stoma ____________________________________________________________
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4. C 4 pathway _______________________________________________________
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5. CAM pathway _____________________________________________________
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MULTIPLE CHOICE Write the correct letter in the blank.
______ 1. The Calvin cycle begins when CO2combines with a five-carbon carbohydrate called
a. RuBP.
b. PGA.
c. 3-G3P.
d. NADPH.
______ 2. For every three molecules of CO 2 that enter the Calvin cycle, the cycle produces six molecules of
a. RuBP.
b. ATP.
c. 3-PGA.
d. NADPH.
______ 3. Organic compounds that can be made from the products of the Calvin cycle include
a. only carbohydrates.
c. only lipids.
b. only amino acids.
d. carbohydrates, amino acids, and lipids.
______ 4. C3 and C4 plants differ in terms of the number of
a. steps in the Calvin Cycle.
b. carbon atoms in the compound that CO2 is initially incorporated into.
c. carbon atoms in the end product of the Calvin cycle.
d. ATP molecules used in the Calvin cycle.
______ 5. As light intensity increases, the rate of photosynthesis
a. continues to decrease.
c. initially decreases and then levels off.
b. continues to increase.
d. initially increases and then levels off.
SHORT ANSWER Answer the questions in the space provided.
1. How many molecules of ATP and NADPH are used in a single turn of the Calvin cycle?
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2. Using (CH2O) as the general formula for a carbohydrate, write the simplest overall equation for
photosynthesis. _____________________________________________________
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3. How do CAM plants differ from both C3 and C4 plants? ____________________
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4. Why does the rate of photosynthesis increase, peak, and then decrease as temperature increases?
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5. Critical Thinking Stomata can open and close in response to changes in the CO2 concentration inside the
leaf. Would you expect stomata to open or close if the CO2 concentration decreased?
Explain. __________________________________________________________
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STRUCTURES AND FUNCTIONS In the blank spaces provided in the diagram, indicate the number
of molecules of each substance that are involved when three CO2 molecules enter the cycle.
The diagram below summarizes the Calvin cycle.