BIOLOGY Ch. 5 NOTES
2/21/23
Life depends on photosynthesis
Chapter 5
Photosynthesis
• Photosynthesis is the process of converting
light (kinetic) energy into chemical (potential)
energy.
• Autotrophs, like this plant, use
photosynthesis to capture energy
from the sun.
• Photosynthetic organisms are
producers—the basis of every
ecosystem on Earth.
•
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Section
5.1
•
•
•
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Photos: (sycamore): Exactostock/SuperStock; (corn): National Geographic Creative Image Collection/Alamy Stock Photo; (cactus): Natphotos/Digital Vision/Getty
Images
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Autotrophs (producers) carry out photosynthesis
Life depends on photosynthesis
• Cyanobacteria carry out photosynthesis, mainly in the water.
•
• Eukaryotes such as algae and plants carry out photosynthesis in
the water and on land.
• No Archaea are known to carry out photosynthesis at all.
•
Figure
5.11
•
Does
Photosynthesis
Occur?
Location of
Photosynthetic
Reactions
Examples
Habitats where
Photosynthesis
Occurs
Yes
Cytoplasm
Cyanobacteria
Aquatic (mostly)
and terrestrial
No
N/A
N/A
N/A
Yes
Chloroplasts
Plants, algae
Aquatic and
terrestrial
Section
5.1
•
Figure
5.2
3
•
Section
5.1
Consumers and
decomposers
obtain their energy
from the molecules
produced during
photosynthesis.
•
Figure
4.2
4
Sunlight Powers Photosynthesis
Sugar is a crucial food source
• Animals, fungi, and
other consumers eat
the producers.
Plants use these simple ingredients to make
sugars, like glucose.
• The sugar is used in
cellular respiration to
make ATP for cells to
use.
This seedling is soaking up
the sun.
Within its leaves,
photosynthesis is
converting sunlight into
food.
Section 5.1
Every ecosystem on
earth is based on
photosynthesis.
Sprout: © Corbis (RF);
"Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison."
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Figure 5.1
•
Section 5.1
•
Figure
4.2
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BIOLOGY Ch. 5 NOTES
2/21/23
All steps of Photosynthesis Occurs in the
Chloroplasts (for eukaryotes)
All Steps of Photosynthesis Occurs in the
Chloroplasts (for eukaryotes)
Gas exchange occurs at leaf pores called stomata.
Mesophyll
cells
What are chloroplasts? Let’s look
back at some plant anatomy.
?
Stoma
CO 2
Section 5.3
Section 5.3
Sprout: © Corbis (RF)
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O 2 + H 2O
Leaves: ©Steve Raymer/NGS Image Collection
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Figure 5.4
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All Steps of Photosynthesis Occurs in the
Chloroplasts (for eukaryotes)
All Steps of Photosynthesis Occurs in the
Chloroplasts (for eukaryotes)
Each leaf contains many mesophyll cells.
Each mesophyll cell contains several chloroplasts.
Mesophyll
cells
CO2
Mesophyll cell
O2
+ H2O
Nucleus
Mitochondrion
Central
vacuole
Leaves: ©Steve Raymer/NGS Image Collection;
Section 5.3
Chloroplasts
TEM
15 µm (false color)
"Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison."
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 5.4
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All Steps of Photosynthesis Occurs in the
Chloroplasts (for eukaryotes)
• the chloroplast contains stacks of membranes called thylakoids
• the thylakoids are stacked together in columns called grana
• the stroma is a semiliquid substance that surrounds the thylakoids
All Steps of Photosynthesis Occurs in the
Chloroplasts (for eukaryotes)
• Embedded in the thylakoid membrane are large protein
structures called photosystems that contain pigments
•
A photosystem
consists of:
1) antenna pigments
2) a reaction center
that contains
chlorophyll
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BIOLOGY Ch. 5 NOTES
2/21/23
Overview of Photosynthesis
Photosynthesis occurs in two stages
• Overall, the reactants are light, water, and carbon dioxide.
(mesophyll): Courtesy of Eldon H. Newcomb,
University of Wisconsin-Madison
LIGHT REACTIONS:
• Overall, the products
are oxygen and sugar.
Section
5.3
•
•
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•
Figure 5.5,
5.7
Electron micrograph by Wm. P. Wergin, courtesy of Eldon H. Newcomb, University of Wisconsin-Madison
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Section 5.4
Figure 5.6
© McGraw Hill, LLC
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1. Capturing energy from sunlight
The light reactions begin photosynthesis
•
•
The light reactions
occur in the
thylakoids and
require water and
light.
Short wavelength (high energy)
Gamma rays
X-rays
Portion of
spectrum
that
reaches
Earth's
surface
ATP and NADPH
are produced, to
carry potential
energy.
Ultraviolet
radiation
Infrared
radiation
Microwaves
Visible light
Wavelength in nanometers
•
DARK (carbon)
REACTIONS:
Energy is used to produce
sugar.
Light energy is captured
and converted to chemical
energy.
400
Violet
450
Blue
Cyan
Green
500
550
Yellow
Orange
600
650
Wavelength
700
Red
750
Radio waves
Long wavelength (low energy)
•
•
Section
5.4
•
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Oxygen gas (O2) is
formed as a
byproduct.
• Figure
5.8
15
The sun releases energy in waves.
But only some wavelengths reach Earth.
Shorter wavelengths have higher energy than longer wavelengths.
Section 5.2
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Figure 5.2
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1. Capturing energy from sunlight
1. Capturing energy from sunlight
Short wavelength (high energy)
Gamma rays
spectrum
that
reaches
Earth's
surface
Ultraviolet
radiation
Infrared
radiation
Microwaves
Wavelength in nanometers
X-rays
Portion of
Visible light
400
Violet
450
Blue
Cyan
Green
500
550
Yellow
Orange
600
650
Wavelength
700
Red
• Light is comprised of packets of
energy called photons
– sunlight has photons of varying
energy levels
• Pigments are molecules that
absorb light energy
– the pigment in human eyes only
absorbs photons of intermediate
energy levels
750
Radio waves
Long wavelength (low energy)
And only some wavelengths are visible to us.
We perceive these wavelengths as colors.
Section 5.2
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Figure 5.2
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BIOLOGY Ch. 5 NOTES
2/21/23
1. Capturing energy from sunlight
Relative absorption (percent)
80
Sunlight
Reflected
light
• chlorophyll absorbs
light at the end of
the visible spectrum,
mainly blue and red
light
60
40
– two versions of
chlorophyll are
present in plants
20
0
400
500
600
700
• chlorophyll a
• chlorophyll b
80
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Chlorophyll a
Chlorophyll b
Carotenoids
Sunlight
Reflected
light
60
40
• So green light is
reflected, which
is why we
perceive leaves to
be green.
20
0
400
500
600
700
Wavelength of light (nanometers)
Wavelength of light (nanometers)
Section 5.2
• No plant pigment
absorbs green
light.
Photosynthetic pigments
Relative absorption (percent)
• Plant pigments
capture visible light
• The main pigment in
plants is chlorophyll
Photosynthetic
pigments
Chlorophyll a
Chlorophyll b
Carotenoids
1. Capturing energy from sunlight
Figure 5.3
Section 5.2
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Figure 5.3
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