1. Chapter 10
Photosynthesis: Using Light to Make Food

2. Biology and Society: Green Energy
Wood has historically been the main fuel used to:
Cook
Warm homes
Provide light at night
Industrialized societies replaced wood with fossil fuels.
To limit the damaging effects of fossil fuels, researchers are investigating the use of biomass (living material) as efficient and renewable energy sources.
© 2010 Pearson Education, Inc.

3. Figure 7.0
Figure 7.0 Sunlight and leaves

4. Fast-growing trees, such as willows:
Can be cut every three years
Do not need to be replanted
Are a renewable energy source
Produce fewer sulfur compounds
Reduce erosion
Provide habitat for wildlife

5. THE BASICS OF PHOTOSYNTHESIS
Is used by plants, some protists, and some bacteria
Transforms light energy into chemical energy
Uses carbon dioxide and water as starting materials
The chemical energy produced via photosynthesis is stored in the bonds of sugar molecules.
Organisms that use photosynthesis are:
Photosynthetic autotrophs
The producers for most ecosystems
Student Misconceptions and Concerns
1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange.
2. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.
Teaching Tips
1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they encounter regularly. Perhaps you might only list those encountered in a single day of college life. The list can be surprising and help to build up your “catalog of examples.”
2. Within the living world, there are many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle seen elsewhere to the extensive folding of the thylakoid membranes.
3. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis.
4. You might wish to discuss the evolution of chloroplasts from photosynthetic prokaryotes if you will not address this subject elsewhere in your course.
5. Students who have not read all of chapter 7 may not realize that glucose is not the direct product of photosynthesis. Although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. (The authors address the production of G3P under the section “The Calvin Cycle” later in this chapter.)
6. Figure 7.3 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates.

6. Photosynthetic Protists Photosynthetic Bacteria
PHOTOSYNTHETIC AUTOTROPHS
Plants
(mostly on land)
Photosynthetic Protists
(aquatic)
Photosynthetic Bacteria
(aquatic) LM
Forest plants
Kelp, a large alga
Micrograph of cyanobacteria
Figure 7.1
Figure 7.1 Photosynthetic autotrophs

7. Chloroplasts: Sites of Photosynthesis
Chloroplasts are:
The site of photosynthesis
Found mostly in the interior cells of leaves
Inside chloroplasts are membranous sacs called thylakoids, which are suspended in a thick fluid, called stroma.
Thylakoids are concentrated in stacks called grana.
The green color of chloroplasts is from chlorophyll, a light-absorbing pigment.
Stomata are tiny pores in leaves where carbon dioxide enters and oxygen exits.
Student Misconceptions and Concerns
1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange.
2. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.
Teaching Tips
1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they encounter regularly. Perhaps you might only list those encountered in a single day of college life. The list can be surprising and help to build up your “catalog of examples.”
2. Within the living world, there are many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle seen elsewhere to the extensive folding of the thylakoid membranes.
3. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis.
4. You might wish to discuss the evolution of chloroplasts from photosynthetic prokaryotes if you will not address this subject elsewhere in your course.
5. Students who have not read all of chapter 7 may not realize that glucose is not the direct product of photosynthesis. Although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. (The authors address the production of G3P under the section “The Calvin Cycle” later in this chapter.)
6. Figure 7.3 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates.

8. Vein Stomata Leaf cross section Figure 7.2-1
CO2
Stomata O2
Leaf cross section
Figure 7.2-1
Figure 7.2 Journey into a leaf (Step 1)

9. Inner membrane Outer membrane Chloroplast Vein Granum Stroma Thylakoid
CO2
Stomata O2 LM
Leaf cross section
Interior cell
TEM
Figure 7.2-2
Figure 7.2 Journey into a leaf (Step 2)

10. CO2 O2 Vein Stomata Leaf cross section Figure 7.2a
Figure 7.2a Leaf cross section

11. Chloroplast Inner membrane Outer membrane Granum Stroma Thylakoid
TEM
Figure 7.2b
Figure 7.2b Chloroplast

12. The Overall Equation for Photosynthesis
In the overall equation for photosynthesis, notice that:
The reactants of photosynthesis are the waste products of cellular respiration.
Student Misconceptions and Concerns
1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange.
2. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.
Teaching Tips
1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they encounter regularly. Perhaps you might only list those encountered in a single day of college life. The list can be surprising and help to build up your “catalog of examples.”
2. Within the living world, there are many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle seen elsewhere to the extensive folding of the thylakoid membranes.
3. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis.
4. You might wish to discuss the evolution of chloroplasts from photosynthetic prokaryotes if you will not address this subject elsewhere in your course.
5. Students who have not read all of chapter 7 may not realize that glucose is not the direct product of photosynthesis. Although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. (The authors address the production of G3P under the section “The Calvin Cycle” later in this chapter.)
6. Figure 7.3 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates.

13. Light energy 6 CO2 6 H2O C6H12O6 6 O2 Photo- synthesis Carbon dioxide
Water
Glucose
Oxygen gas
Figure 7.UN1
Figure 7.UN1 Photosynthesis equation

14. During photosynthesis, water is split into:
In photosynthesis:
Sunlight provides the energy
Electrons are boosted “uphill” and added to carbon dioxide
Sugar is produced
During photosynthesis, water is split into:
Hydrogen
Oxygen
Hydrogen is transferred along with electrons and added to carbon dioxide to produce sugar.
Oxygen escapes through stomata into the atmosphere.
Student Misconceptions and Concerns
1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange.
2. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.
Teaching Tips
1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they encounter regularly. Perhaps you might only list those encountered in a single day of college life. The list can be surprising and help to build up your “catalog of examples.”
2. Within the living world, there are many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle seen elsewhere to the extensive folding of the thylakoid membranes.
3. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis.
4. You might wish to discuss the evolution of chloroplasts from photosynthetic prokaryotes if you will not address this subject elsewhere in your course.
5. Students who have not read all of chapter 7 may not realize that glucose is not the direct product of photosynthesis. Although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. (The authors address the production of G3P under the section “The Calvin Cycle” later in this chapter.)
6. Figure 7.3 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates.

15. A Photosynthesis Road Map
Photosynthesis occurs in two stages:
The light reactions convert solar energy to chemical energy
The Calvin cycle uses the products of the light reactions to make sugar from carbon dioxide
Student Misconceptions and Concerns
1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange.
2. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.
Teaching Tips
1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they encounter regularly. Perhaps you might only list those encountered in a single day of college life. The list can be surprising and help to build up your “catalog of examples.”
2. Within the living world, there are many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle seen elsewhere to the extensive folding of the thylakoid membranes.
3. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis.
4. You might wish to discuss the evolution of chloroplasts from photosynthetic prokaryotes if you will not address this subject elsewhere in your course.
5. Students who have not read all of chapter 7 may not realize that glucose is not the direct product of photosynthesis. Although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. (The authors address the production of G3P under the section “The Calvin Cycle” later in this chapter.)
6. Figure 7.3 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates.

16. H2O Light Light reactions O2 ATP NADPH Chloroplast Figure 7.3-1
Figure 7.3 Photosynthesis roadmap (Step 1)

17. H2O CO2 Light Calvin Light cycle reactions O2 NADP+ ADP P ATP NADPH
Chloroplast
NADP+
ADP P
Calvin
cycle
Light
reactions
ATP
NADPH O2
Sugar
(C6H12O6)
Figure 7.3-2
Figure 7.3 Photosynthesis roadmap (Step 2)

18. THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY
Chloroplasts:
Are chemical factories powered by the sun
Convert solar energy into chemical energy
© 2010 Pearson Education, Inc.
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

19. The Nature of Sunlight
Sunlight is a type of energy called radiation, or electromagnetic energy.
The full range of radiation is called the electromagnetic spectrum.
The distance between the crests of two adjacent waves is called a wavelength.
The full range of radiation, from the very short gamma ray wavelengths to the very long radio signals, is called electromagnetic spectrum.
Visible light is only a small fraction of the spectrum; it consists of the wavelengths that our eyes see as different colors.
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

20. When sunlight shines on a pigmented material, certain wavelengths (colors) of the visible light are absorbed and disappear from the light that is reflected by the material.
For example, we see a pair of jeans as blue because pigments in the fabric absorb the other colors, leaving only light in the blue part of the spectrum to be reflected from the fabric to our eyes.

21. Micro- waves Radio waves Infrared
Increasing wavelength
10–5 nm
10–3 nm
1 nm
103 nm
106 nm
1 m
103 m
Micro-
waves
Radio
waves
Gamma
rays
X-rays UV
Infrared
Visible light
500
600
700
750
Wavelength (nm)
Wavelength =
580 nm
Figure 7.4
Figure 7.4 The electromagnetic spectrum

22. The selective absorption of light by leaves explains why they appear green to us; light of that color is poorly absorbed by chloroplasts (chlorophyll) and is thus reflected toward the observer.
Since energy cannot be destroyed, the absorbed energy must be converted to other forms, such as chemical energy.

23. Light Reflected light Chloroplast Absorbed light Transmitted light
Figure 7.6
Figure 7.6 Why are leaves green?

24. Light Reflected light Chloroplast Absorbed light Transmitted light
Figure 7.6a
Figure 7.6a Why are leaves green?

25. Chloroplast Pigments Chloroplasts contain several pigments:
Chlorophyll a:
Absorbs mostly blue-violet and red light
Participates directly in the light reactions
Chlorophyll b:
Absorbs mostly blue and orange light
Participates indirectly in the light reactions, but it broadens the range of light that a plant can use by conveying absorbed energy to chlorophyll a, which then puts the energy to work in the light reactions.
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

26. Absorb mainly blue-green light
Chloroplasts also contain a family of yellow-orange pigments called Carotenoids:
Absorb mainly blue-green light
Participate indirectly in the light reactions, passing energy to chlorophyll a
Protective function: Absorb and dissipate excessive light energy that might damage chlorophyll
The spectacular colors of fall foliage are due partly to the yellow-orange light reflected from carotenoids. The falling autumn temps cause a decrease in the levels of chlorophyll, allowing the colors of the longer-lasting carotenoids to show through.
All of these chloroplast pigments are built into the thykaloid membranes.
There the pigments are organized into light-harvesting complexes called photosystems.
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

27. Figure 7.7
Figure 7.7 Photosynthetic pigments

28. How Photosystems Harvest Light Energy
The theory of light as waves explains most of light’s properties.
However, Light also behaves as photons, discrete packets of energy. A photon is a fixed quantity of light energy.
The shorter the wavelength of light, the greater the energy of a photon. A photon of violet light packs twice as much energy as a photon of red light.
Chlorophyll molecules absorb photons.
Electrons in the pigment gain energy, electrons have become “excited”, that is, the electrons has been raised from a ground to an excited state.
Excited e- are unstable, so then electrons fall back to their ground state, energy is released as heat or light. (Black gives off heat)
But some pigments emit light after absorbing photons. Ex. Fluorescence.
In the thykaloid membrane, chlorophyll is organized with other molecules into photosystems. A photosystem is a group of chlorophyll and other molecules that function as a light-gathering antenna.
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

29. (a) Absorption Excited state of a photon Light Heat
Light (fluorescence)
Photon
Ground state
Chlorophyll
molecule
(b) Fluorescence
of a glow stick
Figure 7.8
Figure 7.8 Excited electrons in pigments

30. When a photon strikes one of the pigment molecules, the energy jumps from molecule to molecule until it arrives at the reaction center of the photosystem.
The reaction center consists of a chlorophyll a that sits next to another molecule called primary electron acceptor.
This primary e- acceptor traps the light-excited e- from chlorophyll a in the reaction center.
Another team of molecules built into the thykaloids then uses that trapped energy to make ATP and NADPH

31. Chloroplast
Figure 7.9-1
Figure 7.9 A photosystem (Step 1)

32. Chloroplast Thylakoid membrane Figure 7.9-2 Pigment molecules
Figure 7.9 A photosystem (Step 2)

33. Chloroplast Thylakoid membrane Photosystem Transfer of energy
Pigment molecules
Photon
Primary
electron
acceptor
Reaction
center
Electron
transfer
Reaction-
center
chlorophyll a
Antenna pigment
molecules
Transfer of energy
Thylakoid
membrane
Photosystem
Figure 7.9-3
Figure 7.9 A photosystem (Step 3)

34. How the Light Reactions Generate ATP and NADPH
Two types of photosystems cooperate in the light reactions:
The water-splitting photosystem
The NADPH-producing photosystem
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

35. Figure 7.10-1 Primary electron acceptor Light Reaction- center–
Light
Reaction-
center
chlorophyll
H2O 2e –
Water-splitting
photosystem
2 H + + O2
Figure
Figure 7.10 Light reactions (Step 1)

36. Electron transport chain
Energy
to make
ATP
Primary
electron
acceptor 2e –
Electron transport chain
Light
Reaction-
center
chlorophyll
H2O 2e –
Water-splitting
photosystem
2 H + + O2
Figure
Figure 7.10 Light reactions (Step 2)

37. Electron transport chain
Primary
electron
acceptor
NADP 2e –
Energy
to make
ATP
Primary
electron
acceptor 2e –
NADPH 2e –
Light
Electron transport chain
Light
Reaction-
center
chlorophyll
Reaction-
center
chlorophyll
NADPH-producing
photosystem
H2O 2e –
Water-splitting
photosystem
2 H + + O2
Figure
Figure 7.10 Light reactions (Step 3)

38. The light reactions are located in the thylakoid membrane.
An electron transport chain:
Connects the two photosystems
Releases energy that the chloroplast uses to make ATP and NADPH
Student Misconceptions and Concerns
1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.
2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.
3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.
Teaching Tips
1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.
2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the light-generating reactions in glow sticks. Small demonstrations break up lectures and stir attention.
3. Here is a fundamental explanation for a phenomenon that most students have noticed: dark surfaces heat up faster in the sun than do lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them to appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. At high school, they may have learned about light energy and that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.
4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state. Thus, electrons captured at high levels carry more energy than electrons in lower positions. Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.
5. The authors note the similarities between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. If your students have not already read or discussed chemiosmosis in mitochondria, consider assigning the relevant parts of chapter 6 (including Figure 6.11) to show the similarities of these processes.

39. Figure 7.11 – To Calvin cycle Light Light Stroma ATP Thylakoid
NADPH
ATP
ADP  P
NADP H
Stroma
Electron transport chain
Thylakoid
membrane
Photosystem
Photosystem
ATP
synthase
Inside thylakoid
Electron flow 2e – H H
H2O H H H+ O2
Figure 7.11
Figure 7.11 How the thylakoid membrane converts light energy to the chemical energy of NADPH and ATP

40. – To Calvin cycle Light Light Stroma ATP Thylakoid synthase membrane
NADPH
ATP
ADP  P
NADP H
Stroma
Electron transport chain
Thylakoid
membrane
Photosystem
Photosystem
ATP
synthase
Inside thylakoid
Electron flow 2e – H H
H2O H H H O2
Figure 7.11a
Figure 7.11a How the thylakoid membrane converts light energy to the chemical energy of NADPH and ATP

41. – – – – – – – ATP NADPH Water-splitting photosystem NADPH-producing
Photon e –
Photon
Water-splitting
photosystem
NADPH-producing
photosystem
Figure 7.12
Figure 7.12 A hard-hat analogy for the light reactions

42. THE CALVIN CYCLE: MAKING SUGAR FROM CARBON DIOXIDE
Functions like a sugar factory within the stroma of a chloroplast
Regenerates the starting material with each turn
© 2010 Pearson Education, Inc.
Student Misconceptions and Concerns
1. Glucose is not the direct product of the Calvin cycle, as might be expected from the general equation for photosynthesis. Instead, G3P, as noted in the text, is the main product. Clarify for students the diverse uses of G3P in the production of many important plant molecules and the advantages of producing a molecule with this flexibility.
Teaching Tips
1. If you can find examples of potted C3, C4, and CAM plants, consider bringing them to class. Referring to living plants in class helps students understand these abstract concepts. Nice photographs can serve as a substitute.
2. Relate the properties of C3 and C4 plants to the regions of the country where each are grown. Students might generally understand that crops have specific requirements, but may not specifically relate these physiological differences to their geographic sites of production.

43. Three-carbon molecule
CO2 (from air) P
RuBP sugar
Three-carbon molecule P P
Calvin
cycle
Figure
Figure 7.13 The Calvin cycle (Step 1)

44. Three-carbon molecule
CO2 (from air) P
RuBP sugar
Three-carbon molecule
ATP P P
ADP  P
Calvin
cycle
NADPH
NADP
G3P sugar P
Figure
Figure 7.13 The Calvin cycle (Step 2)

45. Three-carbon molecule
CO2 (from air) P
RuBP sugar
Three-carbon molecule
ATP P P
ADP  P
Calvin
cycle
NADPH
NADP
G3P sugar
G3P sugar P P
G3P sugar
Glucose (and
other organic
compounds) P
Figure
Figure 7.13 The Calvin cycle (Step 3)

46. Three-carbon molecule
CO2 (from air) P
RuBP sugar
Three-carbon molecule
ATP P P
ADP  P
ADP  P
Calvin
cycle
NADPH
ATP
NADP
G3P sugar
G3P sugar P P
G3P sugar
Glucose (and
other organic
compounds) P
Figure
Figure 7.13 The Calvin cycle (Step 4)

47. Evolution Connection: Solar-Driven Evolution
C3 plants:
Use CO2 directly from the air
Are very common and widely distributed
© 2010 Pearson Education, Inc.
Student Misconceptions and Concerns
1. Glucose is not the direct product of the Calvin cycle, as might be expected from the general equation for photosynthesis. Instead, G3P, as noted in the text, is the main product. Clarify for students the diverse uses of G3P in the production of many important plant molecules and the advantages of producing a molecule with this flexibility.
Teaching Tips
1. If you can find examples of potted C3, C4, and CAM plants, consider bringing them to class. Referring to living plants in class helps students understand these abstract concepts. Nice photographs can serve as a substitute.
2. Relate the properties of C3 and C4 plants to the regions of the country where each are grown. Students might generally understand that crops have specific requirements, but may not specifically relate these physiological differences to their geographic sites of production.

48. C4 plants:
Close their stomata to save water during hot and dry weather
Can still carry out photosynthesis
CAM plants:
Are adapted to very dry climates
Open their stomata only at night to conserve water
Student Misconceptions and Concerns
1. Glucose is not the direct product of the Calvin cycle, as might be expected from the general equation for photosynthesis. Instead, G3P, as noted in the text, is the main product. Clarify for students the diverse uses of G3P in the production of many important plant molecules and the advantages of producing a molecule with this flexibility.
Teaching Tips
1. If you can find examples of potted C3, C4, and CAM plants, consider bringing them to class. Referring to living plants in class helps students understand these abstract concepts. Nice photographs can serve as a substitute.
2. Relate the properties of C3 and C4 plants to the regions of the country where each are grown. Students might generally understand that crops have specific requirements, but may not specifically relate these physiological differences to their geographic sites of production.

49. C4 Pathway (example: sugarcane) CAM Pathway (example: pineapple)
ALTERNATIVE PHOTOSYNTHETIC PATHWAYS
C4 Pathway
(example: sugarcane)
CAM Pathway
(example: pineapple)
Cell
type 1
CO2
CO2
Night
Four-carbon
compound
Four-carbon
compound
CO2
CO2
Cell
type 2
Calvin
cycle
Calvin
cycle
Sugar
Sugar
Day
C4 plant
CAM plant
Figure 7.14
Figure 7.14 C4 and CAM photosynthesis

50. Light energy 6 CO2 6 H2O C6H12O6 6 O2 Photo- synthesis Carbon dioxide
Water
Glucose
Oxygen gas
Figure 7.UN1
Figure 7.UN1 Photosynthesis equation

51. Calvin cycle Light reactions
CO2
H2O
Light
NADP
ADP P
Calvin
cycle
Light
reactions
ATP
NADPH
Sugar O2
(C6H12O6)
Figure 7.UN2
Figure 7.UN2 Orientation diagram: light reactions

52. Calvin cycle Light reactions
CO2
Light
H2O
NADP
ADP P
Calvin
cycle
Light
reactions
ATP
NADPH
Sugar O2
(C6H12O6)
Figure 7.UN3
Figure 7.UN3 Orientation diagram: Calvin cycle

53. Light energy Photosynthesis Carbon dioxide Water Glucose Oxygen gas
C6H12O6
6 O2
Photosynthesis
Carbon
dioxide
Water
Glucose
Oxygen
gas
Figure 7.UN4
Figure 7.UN4 Summary: photosynthesis equation

54. H2O Chloroplast CO2 Light Stack of thylakoids NADP+ Stroma ADP Calvin
cycle
Light
reactions
ATP
NADPH O2
Sugar
(C6H12O6)
Figure 7.UN5
Figure 7.UN5 Summary: light reactions and Calvin cycle

55. – – NADP+ ADP ATP NADPH Photon Photon H2O NADPH-producing photosystem
acceptor e – 2e –
acceptor 2e
NADPH –
Photon
Electron transport chain
Photon
Chlorophyll
H2O
Chlorophyll
NADPH-producing
photosystem 2e –
Water-splitting
photosystem
2 H 2 1 + O2 +
Figure 7.UN6
Figure 7.UN6 Summary: light reactions

56. CO2 ATP ADP P Calvin cycle NADPH NADP G3P Glucose and other compounds
Figure 7.UN7
Figure 7.UN7 Summary: Calvin cycle