1. Chapter 5 Photosynthesis
Photosynthetic coral © Andrew J. Martinez/Science Source
Copyright © McGraw-Hill Education.  All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

2. Sunlight Powers Photosynthesis
Within the leaves of this seedling, photosynthesis is converting sunlight into food.
Plants need few simple ingredients to make their own food:
Sunlight
Carbon dioxide (CO2)
Water
Section 5.1
Sprout: © Corbis (RF)

3. Plants use these simple ingredients to make sugars, like glucose.
Sunlight Powers Photosynthesis
Plants use these simple ingredients to make sugars, like glucose.
Section 5.1
Figure 5.1
Sprout: © Corbis (RF); Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison.

4. Life Depends On Photosynthesis
Without photosynthesis, neither the plants nor the animal in this image would survive.
Photosynthesis is essential to sustaining life on Earth.
Section 5.1

5. Life Depends On Photosynthesis
Some bacteria and eukaryotes carry out photosynthesis, but archaea do not.
Section 5.1
Figure 5.2

6. Clicker Question #1
Evolution favored the development of photosynthesis because photosynthetic organisms
produce oxygen.
make their own food.
make food for heterotrophs.
use carbon dioxide.
All of the choices are correct.
Flower: © Doug Sherman/Geofile/RF

7. Clicker Question #1
Evolution favored the development of photosynthesis because photosynthetic organisms
produce oxygen.
make their own food.
make food for heterotrophs.
use carbon dioxide.
All of the choices are correct.
Flower: © Doug Sherman/Geofile/RF

8. The Sun Emits a Spectrum of Wavelengths
Short wavelength (high energy)
Gamma rays
Visible light
X-rays
400
Violet
450
Blue
Portion of
spectrum
that
reaches
Earth's
surface
Cyan
Ultraviolet
radiation
500
Green
550
Yellow
Wavelength in nanometers
600
Orange
Infrared
radiation
650
Wavelength
700
Red
Microwaves
750
Radio waves
Long wavelength (low energy)
Photons are packets of light energy. Plants capture photons of visible light.
Section 5.2
Figure 5.3

9. Photosynthetic Pigments Capture Sunlight
Different pigments “specialize” in absorbing different wavelengths.
Sunlight
Reflected
light
700
Wavelength of light (nanometers)
600
500
400 80 60 40 20
Chlorophyll a
Chlorophyll b
Carotenoids
Relative absorption (percent)
Photosynthetic pigments
Chlorophyll a is the primary photosynthetic pigment in plants. It absorbs mostly blue and red light.
Accessory pigments absorb slightly different wavelengths than chlorophyll a.
Section 5.2
Figure 5.4

10. Photosynthetic Pigments Capture Sunlight
No pigment absorbs green light.
Sunlight
Reflected
light
700
Wavelength of light (nanometers)
600
500
400 80 60 40 20
Chlorophyll a
Chlorophyll b
Carotenoids
Relative absorption (percent)
So green light is reflected, which is why we perceive leaves to be green.
Section 5.2
Figure 5.4

11. Clicker Question #2 Why are leaves green?
Heterotrophs see green better than any other color.
Plant pigments absorb green light.
Plant pigments absorb almost every wavelength except for green.
Plant pigments change yellow light that they absorb to green light that we see.
Flower: © Doug Sherman/Geofile/RF

12. Clicker Question #2 Why are leaves green?
Heterotrophs see green better than any other color.
Plant pigments absorb green light.
Plant pigments absorb almost every wavelength except for green.
Plant pigments change yellow light that they absorb to green light that we see.
Flower: © Doug Sherman/Geofile/RF

13. Photosynthesis Occurs in the Chloroplasts
Gas exchange occurs at leaf pores called stomata. +
H2O
CO2 O2
Mesophyll
cells
Stoma
Section 5.2
Figure 5.5
Leaves ©Steve Raymer/National Geographic Stock

14. Photosynthesis Occurs in the Chloroplasts
Each leaf contains many mesophyll cells. +
H2O
CO2 O2
Mesophyll
cells
Mesophyll cell
Nucleus
Central
vacuole
Mitochondrion
Chloroplasts
TEM
(false color)
15 µm
Section 5.2
Leaves: ©Steve Raymer/NGS Image Collection; Sprout: © Corbis (RF); Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison.
Figure 5.5

15. Photosynthesis Occurs in the Chloroplasts
Each mesophyll cell contains several chloroplasts.
Mesophyll cell
Chloroplast
Outer
membrane
DNA
Inner
membrane
Central
vacuole
Chloroplasts
Stroma
Granum
Ribosomes
TEM
(false color)
15 µm
Section 5.2
Figure 5.5
Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison.

16. Photosynthesis Occurs in the Chloroplasts
Each chloroplast contains several grana, or stacks of thylakoids.
Mesophyll cell
Chloroplast
Outer
membrane
DNA
Inner
membrane
Central
vacuole
Chloroplasts
Stroma
Granum
Ribosomes
15 µm
Granum
Pigment molecules
embedded in
thylakoid membrane
Thylakoid
space
Section 5.2
Figure 5.5
Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison.

17. Photosynthesis Occurs in the Chloroplasts
Pigment molecules in the thylakoid membrane capture sunlight.
Mesophyll cell
Chloroplast
Outer
membrane
DNA
Inner
membrane
Central
vacuole
Chloroplasts
Stroma
Granum
Ribosomes
15 µm
Granum
Pigment molecules
embedded in
thylakoid membrane
Thylakoid
space
Section 5.2
Figure 5.5
Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison.

18. Photosynthesis Occurs in the Chloroplasts
A photosystem is a large protein structure in the thylakoid membrane.
Section 5.2
Figure 5.6

19. Photosynthesis Occurs in the Chloroplasts
A photosystem consists of antenna pigments and a reaction center that contains chlorophyll.
Section 5.2
Figure 5.6

20. Clicker Question #3
Of the following list of plant structures, which is the second smallest?
chloroplast
granum
mesophyll cell
chlorophyll
thylakoid
Flower: © Doug Sherman/Geofile/RF

21. Clicker Question #3
Of the following list of plant structures, which is the second smallest?
chloroplast
granum
mesophyll cell
chlorophyll
thylakoid
Flower: © Doug Sherman/Geofile/RF

22. Photosynthesis Occurs in Two Stages
Section 5.3
Figure 5.7

23. The Light Reactions Begin Photosynthesis
The light reactions occur in the thylakoids and require water and light.
ATP and NADPH are produced. Oxygen gas (O2) is a byproduct.
Section 5.4
Figure 5.8

24. The Light Reactions Begin Photosynthesis
The photosystems are part of an electron transport chain that converts light energy into ATP and NADPH.
Section 5.4
Figure 5.8

25. The Light Reactions Begin Photosynthesis
Photosystem II produces ATP
Light energy transferred to reaction center
Section 5.4
Figure 5.8

26. The Light Reactions Begin Photosynthesis
Two electrons ejected
Water is split to replace electrons
O2 is a byproduct
Ejected electrons move down transport chain
Section 5.4
Figure 5.8

27. The Light Reactions Begin Photosynthesis
Photosystem II produces ATP
Ejected electrons move down transport chain
H+ is pumped into thylakoid
Section 5.4
Figure 5.8

28. The Light Reactions Begin Photosynthesis
H+ leaves through ATP synthase
ATP is produced by chemiosmotic phosphorylation
Section 5.4
Figure 5.8

29. The Light Reactions Begin Photosynthesis
Photosystem I produces NADPH
Electrons reach photosystem I
Energy from light again ejects electrons into a transport chain
Section 5.4

30. The Light Reactions Begin Photosynthesis
Electrons reduce NADP+ to NADPH
Section 5.4

31. The Light Reactions Begin Photosynthesis
Some chemicals, such as the weed killers DCMU and Paraquat, block the light reactions.
Section 5.4
Figure 5.A

32. Clicker Question #4
How do the light reactions produce ATP? (Select the one best answer.)
Potential energy stored in a hydrogen ion gradient is used to synthesize ATP.
Photosystem I directly adds a phosphate to ADP.
Photosystem II directly adds a phosphate to ADP.
Energy released by electrons is directly used to synthesize ATP.
Flower: © Doug Sherman/Geofile/RF

33. Clicker Question #4
How do the light reactions produce ATP? (Select the one best answer.)
Potential energy stored in a hydrogen ion gradient is used to synthesize ATP.
Photosystem I directly adds a phosphate to ADP.
Photosystem II directly adds a phosphate to ADP.
Energy released by electrons is directly used to synthesize ATP.
Flower: © Doug Sherman/Geofile/RF

34. Photosynthesis Occurs in Two Stages
Section 5.5
Figure 5.7

35. Carbon Reactions Produce Carbohydrates
The carbon reactions occur in the stroma.
Carbon reactions use carbon dioxide (CO2) and produce sugars.
In the carbon reactions, the chloroplast will use the ATP and NADPH produced in the light reactions.
Section 5.5
Figure 5.9

36. Carbon Reactions Produce Carbohydrates
CO2
These are the carbon reactions, also known as the Calvin cycle.
Section 5.5
Figure 5.9

37. Carbon Reactions Produce Carbohydrates
CO2
Carbon fixation
Rubisco adds CO2 to RuBP
An unstable 6-carbon molecule is produced
Section 5.5
Figure 5.9

38. Carbon Reactions Produce Carbohydrates
CO2
PGAL synthesis
ATP and NADPH from light reactions are cashed in
PGA is converted to PGAL
Section 5.5
Figure 5.9

39. Carbon Reactions Produce Carbohydrates
CO2
PGAL exit
One PGAL leaves
Multiple PGALs combine to form sugars
Section 5.5
Figure 5.9

40. Carbon Reactions Produce Carbohydrates
CO2
Regeneration of RuBP
RuBP is reformed, starting the cycle anew
Section 5.5
Figure 5.9

41. Clicker Question #5
How does a plant cell use the ATP that it produces in the light reactions?
to fuel processes and reactions throughout the cell
to fuel the carbon reactions
to break down glucose
to convert NADP+ to NADPH
Flower: © Doug Sherman/Geofile/RF

42. Clicker Question #5
How does a plant cell use the ATP that it produces in the light reactions?
to fuel processes and reactions throughout the cell
to fuel the carbon reactions
to break down glucose
to convert NADP+ to NADPH
Flower: © Doug Sherman/Geofile/RF

43. Carbon Reactions Produce Carbohydrates
Plants use glucose for energy and to build polysaccharides.
Glucose
Section 5.6
Cellulose: © Dr. Dennis Kunkel; starch © Gary Gaugler/Visuals Unlimited

44. Plants Use Different Carbon Fixation Pathways
C3 plants, C4 plants, and CAM plants all use slightly different carbon fixation pathways.
Section 5.6
Figure 5.10

45. Plants Use Different Carbon Fixation Pathways
Notice the different leaf anatomy and Calvin cycle position.
The Calvin cycle occurs here.
Section 5.6
Figure 5.10

46. Plants Use Different Carbon Fixation Pathways
Section 5.6
Tree: © Tony Sweet/Digital Vision/Getty Images RF; corn: © Joeseph Sohm-Visions of America/Getty Images RF; cactus: © Digital Vision/Getty Images RF
Figure 5.11

47. Plants Use Different Carbon Fixation Pathways
Section 5.6
Tree: © Tony Sweet/Digital Vision/Getty Images RF; corn: © Joeseph Sohm-Visions of America/Getty Images RF; cactus: © Digital Vision/Getty Images RF
Figure 5.11

48. Photosynthetic coral © Andrew J. Martinez/Science Source
5.6 Mastering Concepts
How is the CAM pathway like C4 metabolism, and how is it different?
Photosynthetic coral © Andrew J. Martinez/Science Source