Biology: Life on Earth 7e
Student Self Test Questions and Answers
Chapter 7: Capturing Solar Energy: Photosynthesis
Self Test
1. In most land plants, photosynthesis occurs in cells of the __________ of the leaves, because these cells contain
the largest numbers of chloroplasts.
a. epidermis
b. stomata
c. cuticle
d. mesophyll
e. vascular bundles
2. Light energy is initially captured by "photosystems" within thylakoid membranes. Photosystems are organized
arrays of __________.
a. proteins
b. chlorophyll molecules
c. pigment molecules such as carotenoids
d. all of the above
e. none of the above
3. Why is carbon dioxide a key molecule in the light-independent reactions of photosynthesis?
a. Carbon dioxide provides electrons to replace those lost by chlorophyll during the light-dependent
reactions.
b. Carbon dioxide, together with water, is the raw material for the synthesis of sugars, which are the
key products of the light-independent reactions.
c. Carbon dioxide inhibits the light-independent reactions of photosynthesis.
d. Carbon dioxide is the major product of the light-independent reactions of photosynthesis.
4. What is photorespiration?
a. Photorespiration is the process by which plants produce energy at night.
b. Photorespiration is the process by which plant cells cool off in hot climates.
c. Photorespiration is the process that prevents sugar production in C3 plants when CO2 levels are
low and O2 levels are high.
d. Photorespiration is the process by which plants capture light energy and convert it into ATP.
5. In the light-dependent reactions of photosynthesis, ATP is produced by chemiosmosis. Describe this process.
a. Chemiosmosis is the process by which water moves across a semipermeable membrane.
b. As high-energy electrons move from carrier to carrier in the electron transport system of the
thylakoid membrane, some of the energy is captured to pump hydrogen ions across it.
c. When light strikes the chlorophyll molecules, water is moved via osmosis across the chloroplast
membrane. When water moves back across the membrane, ATP is generated.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
6. A lovely tree called the flowering plum has beautiful pink flowers in spring and deep-purple leaves in summer.
What types of pigments are plentiful in this plant? Can photosynthesis occur in these purple leaves? Explain your
answer.
a. The leaves probably contain a high amount of phycocyanins and carotenoids and less
chlorophyll than do plants with green leaves. They can still perform photosynthesis, because
photosynthesis can occur to some extent at all wavelengths of light.
b. The leaves probably contain a high amount of chlorophyll and carotenoids and lesser amounts of
phycocyanins than do plants with green leaves.
c. The leaves probably contain a high amount of carotenoids and lesser amounts of phycocyanins
and chlorophyll than do plants with green leaves.
7. Take a deep breath and slowly exhale. The oxygen in that breath is being used by your mitochondria in reactions
that produce ATP from sugars and other food molecules you ate. Where did that oxygen come from originally?
a. The oxygen in the atmosphere is produced by the breakdown of carbon dioxide during
photosynthesis.
b. Plants produce the oxygen via the process of photorespiration when they break down sugars in
their mitochondria.
c. The oxygen in the air is produced by the splitting of water during the light-dependent reactions of
photosynthesis.
d. Plants produce the oxygen via the process of photorespiration, in which they break down sugars
at night when photosynthesis cannot occur.
8. A scientist studying photosynthesis illuminated a culture of algae with bright visible light. She then turned out the
light and simultaneously began to bubble radioactive CO2 gas into the culture. After 30 minutes, she stopped the
reaction and measured the amount of radioactivity inside the cells. What did she find? Explain your answer.
a. There was no radioactivity inside the cells, because the CO 2 is used to produce O2 in the lightdependent reactions. Thus, there was radioactivity in the air above the culture but not in the cells.
b. There was radioactivity in the cells, because the CO2 is used to synthesize sugar, even in the
dark.
c. There was no radioactivity in the cells, because light is required to produce sugars from CO 2 and
water.
d. There was radioactivity inside the cells, because CO2 is used to replace the electrons that were
lost by chlorophyll when the lights were turned on.
9. Imagine that you are trying to set up a large fish tank and want to select a colored light that will show off the fish to
best advantage but will also allow the green plants in the tank to grow and stay healthy. You decide to measure the
efficiency of photosynthesis by looking at the production of oxygen bubbles on the leaves (see Figure 7-5). At first,
you use a white fluorescent lamp and see many oxygen bubbles on the leaves, indicating that photosynthesis is
occurring normally. Next, you put a sheet of green cellophane between the white light and the water so that the light
coming through to the tank appears green. Will the oxygen bubbles remain the same, increase, decrease, or
disappear? Explain your answer.
a. The bubbles will remain constant because photosynthesis can occur to some extent at all visible
wavelengths of light.
b. The bubbles will increase; because chlorophyll is green, photosynthesis will work best if leaves
are exposed to green light.
c. The bubbles will decrease, because green light cannot be absorbed by chlorophyll.
d. The bubbles will disappear, because photosynthesis cannot occur in green light.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
10. Which of the following is a true statement about photosynthesis?
a. In photosynthesis, inorganic molecules such as carbon dioxide and water react to produce
organic, energy-rich molecules such as glucose.
b. In photosynthesis, oxygen is used to help break down glucose.
c. Photosynthesis is an exergonic reaction.
d. Photosynthesis is a process that is carried out primarily by autotrophic prokaryotic bacteria.
11. Leaves include a number of structural modifications for the purpose of photosynthesis, including __________.
a. adjustable openings in the surface of the leaf that permit the passage of carbon dioxide, water,
and oxygen
b. a waxy covering on the surface of the leaf that is designed to reduce evaporation
c. photosynthetic mitochondria
d. Both the first and second answers are correct.
12. During photosynthesis, electrons are continuously lost from the reaction center of photosystem II. What source is
used to replace these electrons?
a. sunlight
b. oxygen
c. water
d. carbon dioxide
13. The term carbon fixation refers to __________.
a. the loss of carbon during glucose synthesis
b. the incorporation of atmospheric carbon dioxide into a larger organic molecule
c. the synthesis of glyceraldehyde-3-phosphate
d. the regeneration of ribulose bisphosphate
14. Photorespiration occurs when __________.
a. oxygen is combined with ribulose bisphosphate
b. carbon dioxide is combined with ribulose bisphosphate
c. stomata are closed
d. Both the first and third answers are correct.
15. How have C4 plants adapted to environmental conditions that would result in increased photorespiration?
a. C4 plants have substituted phosphoenolpyruvate (PEP) for ribulose bisphosphate.
b. PEP specifically combines with carbon dioxide even in the face of high oxygen concentrations.
c. A molecule transports the fixed carbon into a cell type where the normal C3 synthetic metabolism
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
would be favored due to the now high concentrations of carbon dioxide.
d. all of the above
16. The stomata __________.
a. allow oxygen to exit
b. allow carbon dioxide to enter
c. allow light to enter
d. allow excess heat to exit
e. The first two answers are correct.
17. You have just discovered a new plant with red-orange leaves. What wavelengths of visible light are NOT being
absorbed by this pigment?
a. green, blue, and violet
b. green and yellow
c. green
d. red and orange
e. blue and violet
18. In the light-dependent reactions of photosynthesis the difference in hydrogen ion concentration across the
thylakoid membrane is used to generate __________.
a. NADPH
b. glucose
c. FADH2
d. ATP
e. oxygen
19. Which of the following represents the products of the light-dependent reactions of photosynthesis? For what
process are these products needed?
a. ATP and oxygen; photosystem I
b. NADPH and glucose; light-independent reactions
c. carbon dioxide and water; Calvin-Benson cycle
d. NADH and ADP; cellular respiration
e. NADPH and ATP; Calvin-Benson cycle
20. Which of the following is NOT required for the light-independent reactions of photosynthesis?
a. ATP
b. stroma
c. NADPH
d. CO2
e. H2O
f. O2
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
21. ____________________ converts the energy of sunlight into chemical energy.
22. ____________________ are organisms that can produce their own food in their cells.
23. Photosynthesis takes place within ____________________.
24. In the ____________________, light energy is converted to chemical energy in the form of ATP and NADPH.
25. In the ____________________, chemical energy is used to drive the formation of glucose.
.
26. ____________________ is the key light-capturing molecule found in chloroplasts.
27. Complete the following cycle of reactions.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
28. Using the image below, provide the connections between photosynthesis and cellular respiration.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
29. Label the structures in this cross section of a leaf.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
30. Below is a diagram of light-dependent reactions of photosynthesis. Place the descriptions of the steps in this
process next to the appropriate portion of the diagram.
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