MAIN SOURCE OF ENERGY FOR
LIFE ON EARTH?
• THE SUN!!
THE BASICS OF PHOTOSYNTHESIS
• Almost all plants are photosynthetic autotrophs, as
are some bacteria and protists
– Autotrophs generate their own organic matter through
photosynthesis
– Sunlight energy is transformed to energy stored in the
form of chemical bonds
(c) Euglena
(b) Kelp
(a) Mosses, ferns, and
flowering plants
(d) Cyanobacteria
Light Energy Harvested by Plants &
Other Photosynthetic Autotrophs
6 CO2 + 6 H2O + light energy → C6H12O6 + 6
O2
Energy needs of life
• All life needs a constant input of energy
• Heterotrophs (Animals)
• get their energy from “eating others”
• eat food = other organisms = organic molecules
• make energy through respiration
• Autotrophs (Plants)
• get their energy from “self”
• get their energy from sunlight
• build organic molecules (food) from CO2
• make energy & synthesize sugars through
photosynthesis
Energy needs of life
• Heterotrophs
• consumers
• Animals
• Protists
• fungi
• most bacteria
• Autotrophs
• producers
• plants
• photosynthetic bacteria
(blue-green algae)
How are they connected?
Heterotrophs
making energy & organic molecules from ingesting organic molecules
glucose + oxygen  carbon + water + energy
dioxide
C6H12O6 +
6O2
 6CO2 + 6H2O + ATP
exergonic
Autotrophs
making energy & organic molecules from light energy
Where’s
the
ATP?
carbon + water + energy  glucose + oxygen
dioxide
6CO2 + 6H2O + light  C6H12O6 + 6O2
energy
endergonic
Energy cycle
sun
Photosynthesis
plants
CO2
glucose
H2O
animals, plants
Cellular Respiration
The Great Circle
of Life,Mufasa!
ATP
O2
Food Chain
THE FOOD WEB
What does it mean to be a plant
• Need to…
• collect light energy
• transform it into chemical energy
ATP
• store light energy
• in a stable form to be moved around
the plant & also saved for a rainy day
glucose
• need to get building block atoms
from the environment
• C,H,O,N,P,S
• produce all organic molecules
CO2
needed for growth
• carbohydrates, proteins, lipids, nucleic acids
H2O
N
K P
…
Plant structure
• Obtaining raw materials
• sunlight
• leaves = solar collectors
• CO2
• stomata = gas exchange
• H 2O
• uptake from roots
• nutrients
• N, P, K, S…
• uptake from roots
stomate
transpiration
WHY ARE PLANTS GREEN?
Electromagnetic Spectrum and
Visible Light
Gamma
rays
X-rays
UV
Infrared &
Microwaves
Visible light
Wavelength (nm)
Radio waves
WHY ARE PLANTS GREEN?
Different wavelengths of visible light are seen by
the human eye as different colors.
Gamma
rays
X-rays
UV
Infrared
Visible light
Wavelength (nm)
Microwaves
Radio
waves
The feathers of male cardinals
are loaded with carotenoid
pigments. These pigments
absorb some wavelengths of
light and reflect others.
Sunlight minus absorbed
wavelengths or colors
equals the apparent color
of an object.
Why are plants green?
Transmitted light
WHY ARE PLANTS GREEN?
Plant Cells
have Green
Chloroplasts
The thylakoid
membrane of the
chloroplast is
impregnated with
photosynthetic
pigments (i.e.,
chlorophylls,
carotenoids).
THE COLOR OF LIGHT SEEN IS THE
COLOR NOT ABSORBED
• Chloroplasts
absorb light
energy and
convert it to
chemical energy
Light
Reflected
light
Transmitted
light
Chloroplast
Absorbed
light
• What
wavelengths
of light have
the most
energy?
• Red, blues,
violets = most
• Yellows &
greens = least
AN OVERVIEW OF PHOTOSYNTHESIS
• Photosynthesis is the process by which
autotrophic organisms use light energy to
make sugar and oxygen gas from carbon
dioxide and water
Carbon
dioxide
Water
Glucose
PHOTOSYNTHESIS
Oxygen
gas
Who do we have to thank for all
of this??
• Many scientists but 3 got the ball rolling.
• Jan van Helmont
- water made up mass
• Joseph Priestley
- mint “freshened” air under jar
• Jan Ingenhousz
- plants needed light to remain alive
• The complete timeline?
What are we looking at today?
Stomata (stoma)
• Pores in a plant’s cuticle through which water
and gases are exchanged between the plant
and the atmosphere.
Oxygen
(O2)
Carbon Dioxide
(CO2)
Guard Cell
Guard Cell
Have the ability to open and close.
• Closed at night & dry days to save water.
• Open to allow exchange of CO2 and O2
• When water plentiful guard cells swell.
• When dry, vacuoles shrink closing stoma
stomate
transpiration
The Photosynthesis Equation
Light energy
O2
ADP
+
NADP
Sugar
CO2
+
H20
Light and Pigments
•What is the role of light and chlorophyll in photosynthesis?
Light and Pigments
•Light and Pigments
•How do plants capture the energy of sunlight?
In addition to water and carbon dioxide, photosynthesis requires light
and chlorophyll.
Light and Pigments
•Plants gather the sun's energy with light-absorbing molecules called
pigments.
•The main pigment in plants is chlorophyll.
•There are two main types of chlorophyll:
• chlorophyll a
• chlorophyll b
Pigments in Plants
• Pigments are light-absorbing
molecules
• Different
pigments absorb
or reflect
different colors
Chlorophyll a
• wavelengths
absorbed:
blue-violet
and red
• Reflects:
grass green
Wavelength
Chlorophyll b
• Absorbs: blue
and orange
• Reflects:
yellow-green
•An
accessory
chlorophyll
in plants
Other pigments in plants
Carotenoids-orange
• Absorb: blue-
green
• Reflect:
yellow-orange
FYI Why do leaves change color?
• As fall comes there are
shorter days of
sunlight
• Less photosynthesis
means less food for
plants.
• Chlorophyll breaks
down and exposes
the other colors that
were there all along,
but were masked by
the green
chlorophyll.
WORKSHEET
• “Absorption of
Chlorophyll”
• Photosynthesis: The
Action Spectrum for
Photosynthesis
(experiment link)
Light and Pigments
• Chlorophyll absorbs light well in the blue-violet and red regions of the
visible spectrum.
Estimated Absorption (%)
100
80
60
Chlorophyll b
Chlorophyll a
40
20
0
(nm)
400 450 Wavelength
500 550 600
650 700 750
Wavelength (nm)
Light and Pigments
• Chlorophyll does not absorb light well in the green region of the
spectrum. Green light is reflected by leaves, which is why plants look
green.
Estimated Absorption (%)
100
80
60
Chlorophyll b
Chlorophyll a
40
20
0
400 450 500 550 600 650 700 750
Wavelength (nm)
Light and Pigments
• Light is a form of energy, so any compound that absorbs light also
absorbs energy from that light.
• When chlorophyll absorbs light, much of the energy is transferred
directly to electrons in the chlorophyll molecule, raising the energy levels
of these electrons.
• These high-energy electrons are what make photosynthesis work.
8-3 The Reactions of
Photosynthesis
Inside a Chloroplast
• Inside a Chloroplast
• In plants, photosynthesis takes place inside chloroplasts.
Plant
Chloroplast
Plant cells
Inside a Chloroplast
• Chloroplasts contain thylakoids—saclike photosynthetic membranes.
Single
thylakoid
Chloroplast
Inside a Chloroplast
• Thylakoids are arranged in stacks known as grana. A singular stack is
called a granum.
Granum
Chloroplast
Inside a Chloroplast
• Proteins in the thylakoid membrane organize chlorophyll and other
pigments into clusters called photosystems, which are the lightcollecting units of the chloroplast.
Photosystems
Chloroplast
Chloroplast Diagram
• Stroma = thick fluid
between the
thylakoids
• thylakoids = disks
within the
chloroplasts
• granum=stack of
thylakoids (grana pl.)
Inside a Chloroplast
•The reactions of photosystems include:
the light-dependent reactions and the
light-independent reactions, or Calvin
cycle.
•The light-dependent reactions take
place within the thylakoid membranes.
•The Calvin cycle takes place in the
stroma, which is the region outside the
thylakoid membranes.
GRANA
•What is the difference
between grana and
granum?
STROMA
• So what’s the difference between
the stoma and the stroma?
• STOMA = opening in lower
epidermis
• STROMA = area around thylakoid
disks in the chloroplast
Chloroplast Diagram
Stromal lamella
D.
Outer
Membrane
= connect grana
Thylakoid
membrane
Inner
Membrane
Intermembrane
Space
Thylakoid
space
Chloroplasts TEM
stacks of
thylakoid disks =
• Note the
grana
• Note area between =
stroma
H2O
Inside
a Chloroplast
Light
CO2
NADP+
ADP + P
Lightdependent
reactions
Calvin
Calvin
cycle
Cycle
Chloroplast
O2
Sugars
Electron Carriers
• Electron Carriers
• When electrons in chlorophyll absorb sunlight, the electrons gain a great
deal of energy.
• Cells use electron carriers to transport these high-energy electrons from
chlorophyll to other molecules.
THYLAKOIDS
Summary IN
Summary OUT
Electron Carriers
• One carrier molecule is NADP+.
• Electron carriers, such as NADP+, transport electrons.
• NADP+ accepts and holds 2 high-energy electrons along with a
hydrogen ion (H+). This converts the NADP+ into NADPH.
Nice Little Photosynthesis Movies
• VCAC: Cellular Processes: Photosynthesis: The Movie
• VCAC: Cellular Processes: Photosystem II: The Movie
Overview of Photosynthesis
What happens here?
• Light Dependent
Reaction (LDR)
• Converts light
energy to
chemical energy
+ O2
• Light Independent
Reaction (LIR)
• Assembles
sugar
molecules
using CO2
Where does energy come from?
• Light Dependent
Reaction LDR
• Uses light
energy
• Light
Independent
Reaction LIR
• (Calvin Cycle)
• uses ATP and
NADPH (from
LDR)
PSI and PSII
• PSI and PSII animation
• Another PSI and PSII animation
Where is it located in the cell?
• LDR
• occurs in
thylakoid
membranes of
chloroplast’s
grana
• LIR (aka
Calvin cycle)
• occurs in
stroma of
chloroplast
Final Products of Each?
• LDR
• LIR
•ATP and
•sugar
NADPH
•Also O2
Electron Carriers
• The conversion of NADP+ into NADPH is one way some of the energy of
sunlight can be trapped in chemical form.
• The NADPH carries high-energy electrons to chemical reactions
elsewhere in the cell.
• These high-energy electrons are used to help build a variety of
molecules the cell needs, including carbohydrates like glucose.
Light-Dependent Reactions
• What happens in the light-dependent reactions?
Light-Dependent Reactions
• Light-Dependent Reactions
• The light-dependent reactions require light.
• The light-dependent reactions produce oxygen gas and convert ADP and NADP+
into the energy carriers ATP and NADPH.
Light-Dependent Reactions
•Photosynthesis begins when pigments in photosystem II absorb light,
Light-Dependent
Reactions
increasing their energy level.
Photosystem II
•These high-energy electrons are passed on to the electron transport chain.
Light-Dependent
Reactions
Photosystem II
High-energy
electron
Electron
carriers
• Enzymes on the thylakoid membrane break water molecules into:
Light-Dependent
Reactions
Photosystem II
2H2O
High-energy
electron
Electron
carriers
• hydrogen ions
• oxygen atoms
• energized electrons
Light-Dependent Reactions
Photosystem II
+
O2
2H2O
High-energy
electron
Electron
carriers
The energized electrons from water replace the high-energy electrons that
Light-Dependent
Reactions
chlorophyll lost to the electron transport chain.
Photosystem II
+
2H2O
High-energy
electron
O2
As plants remove electrons from water, oxygen is left behind and is released into
Light-Dependent
Reactions
the air.
Photosystem II
+
2H2O
High-energy
electron
O2
The hydrogen ions left behind when water is broken apart are released inside
Light-Dependent
Reactions
the thylakoid membrane.
Photosystem II
+
2H2O
High-energy
electron
O2
Energy from the electrons is used to transport H+ ions from the stroma into the
inner thylakoid space.
Light-Dependent Reactions
Photosystem II
+
2H2O
O2
High-energy electrons move through the electron transport chain from
Light-Dependent
Reactions
photosystem II to photosystem I.
Photosystem II
+
O2
2H2O
Photosystem I
Pigments in photosystem I use energy from light to re-energize the
Light-Dependent
Reactions
electrons.
+
O2
2H2O
Photosystem I
NADP+ then picks up these high-energy electrons, along with H+ ions, and
becomes NADPH.
Light-Dependent Reactions
+
O2
2H2O
2 NADP+
2
2
NADPH
As electrons are passed from chlorophyll to NADP+, more H+ ions are
pumped across the membrane.
Light-Dependent Reactions
+
O2
2H2O
2 NADP+
2
2
NADPH
Soon, the inside of the membrane fills up with positively charged hydrogen
Light-Dependent
Reactions
ions, which makes the outside of the membrane negatively charged.
+
O2
2H2O
2 NADP+
2
2
NADPH
The difference in charges across the membrane provides the energy to make
Light-Dependent
Reactions
ATP.
+
O2
2H2O
2 NADP+
2
2
NADPH
H ions cannot cross the membrane
directly.
Light-Dependent
Reactions
+
ATP synthase
+
O2
2H2O
2 NADP+
2
2
NADPH
The cell membrane contains a protein called ATP synthase that allows H+ ions
to pass through it.
Light-Dependent Reactions
ATP synthase
+
O2
2H2O
2 NADP+
2
2
NADPH
As H+ ions pass through ATP synthase, the protein rotates.
Light-Dependent Reactions
ATP synthase
+
O2
2H2O
2 NADP+
2
2
NADPH
As it rotates, ATP synthase binds ADP and a phosphate group together to produce
ATP.
Light-Dependent Reactions
ATP synthase
+
O2
2H2O
ADP
2 NADP+
2
2
NADPH
Because of this system, light-dependent electron transport produces not only
high-energy electrons but ATP as well.
Light-Dependent Reactions
ATP synthase
+
O2
2H2O
ADP
2 NADP+
2
2
NADPH
Light-Dependent Reactions
•The light-dependent reactions use water, ADP, and
NADP+.
•The light-dependent reactions produce oxygen, ATP, and
NADPH.
•These compounds provide the energy to build energy-
containing sugars from low-energy compounds.
The Calvin Cycle
•
What is the Calvin cycle?
Calvin Cycle
•Occurs in
stroma of
chloroplasts
7.11 Review of Photosynthesis
Summary: Calvin Cycle
Overall Equation
The Calvin Cycle
• The Calvin Cycle
• ATP and NADPH formed by the light-dependent reactions contain an
abundance of chemical energy, but they are not stable enough to store
that energy for more than a few minutes.
• During the Calvin cycle plants use the energy that ATP and NADPH
contain to build high-energy compounds that can be stored for a long
time.
•
The Calvin Cycle
• The Calvin cycle uses ATP and NADPH from the light-dependent reactions to
produce high-energy sugars.
• Because the Calvin cycle does not require light, these reactions are also called the lightindependent reactions.
•
The Calvin Cycle
•Six carbon dioxide
molecules enter the cycle
from the atmosphere and
combine with six 5-carbon
molecules.
• CO2 Enters the Cycle
The Calvin Cycle
•The result is twelve
3-carbon molecules,
which are then
converted into
higher-energy forms.
energy for this
conversion comes from ATP and high-energy electrons
The•TheCalvin
Cycle
from NADPH.
•
Energy Input
12
12 ADP
12 NADPH
12 NADP+
The Calvin Cycle
•Two of twelve 3-carbon molecules are removed from the cycle.
•
Energy Input
12
12 ADP
12 NADPH
12 NADP+
The Calvin Cycle
•The molecules are used to produce sugars, lipids, amino acids and other
compounds.
•
12
12 ADP
12 NADPH
12 NADP+
6-Carbon sugar
produced
Sugars and other compounds
The Calvin Cycle
• The 10 remaining 3-carbon molecules are converted back into six 5-
carbon molecules, which are used to begin the next cycle.
•
12
12 ADP
6 ADP
12 NADPH
6
12 NADP+
5-Carbon Molecules
Regenerated
Sugars and other compounds
The
Calvin Cycle
• The two sets of photosynthetic reactions work together.
• The light-dependent reactions trap sunlight energy in chemical form.
• The light-independent reactions use that chemical energy to produce stable, highenergy sugars from carbon dioxide and water.
Factors Affecting Photosynthesis
• Factors Affecting Photosynthesis
• Many factors affect the rate of photosynthesis, including:
• Water
• Temperature
• Intensity of light
Which equation summarizes
photosynthesis?
• A. water + starch ---> glucose + glucose + glucose
B. water + carbon dioxide ---> oxygen + glucose +
water
C. glucose + oxygen ---> water + carbon dioxide +
ATP
D. glucose + glucose ---> maltose + water
ANSWER
water + carbon
dioxide ---> oxygen +
glucose + water
•B.
In what organelle does photosynthesis
occur?
• A. the nucleus
B. chloroplasts
C. the vacuole
D. the cell wall
ANSWER
•B. Chloroplast
QUESTION:
• Four identical plants are grown under different
colored light bulbs. Under which color will the release
of oxygen gas be slowest?
A. Green
• B. blue
C. orange
D. red
ANSWER:
•A. Green
QUIZ TIME
• The reason why ADP + P form ATP in thylakoid
membranes is…
A movement of electrons between photosystem
II and photosystem I.
• B oxidation of water
• C oxidation of NADPH
• D absorption of photons by chloroplast pigments
• E higher concentration of H+ inside versus
outside the thylakoid membranes
•
ANSWER
• E. a higher concentration of H+
ions inside vs. outside the
thylakoid membranes
QUIZ TIME
• Water is broken down and the electrons from water pass
•
•
•
•
•
through photosystem II and photosystem I before adding
e- to:
A carbon dioxide
B NADP+
C plastoquinones
D FAD
E rubisco
ANSWER
• NADP+ to make higher energy
NADPH
• REVIEW ALL OF CHAPTER 8
QUIZ TIME
• Which of the following would have the smallest effect
on the rate of photosynthesis in a green plant?
A. carbon dioxide concentration
B. light intensity
C. oxygen concentration
D. water available
ANSWER:
•C. oxygen concentration
QUIZ TIME
• During photosynthetic electron transport, the interior
compartment of the thylakoid membranes becomes:
• A. more concentrated with ATP
• B. more concentrated with H+ ions
• C. less concentrated with H+ ions
HINT: Distribution of H+ ions
• Light Rx
• Dark Rx
• more inside
• Even in and out
ANSWER
•More concentrated
with H+ ions
QUIZ TIME
• Which of the following is
produced during
photosynthesis?
A. carbon dioxide
B. lactic acid
C. DNA
D. PGAL
•
ANSWER
•D. PGAL
QUIZ TIME
• Atmospheric oxygen that is inhaled by animals comes
from:
A. carbon dioxide molecules split during the light
reactions
B. carbon dioxide split during the dark reactions
C. water molecules split during the light reactions
D. water molecules split during the dark reactions
ANSWER
•C. water molecules
split during the light
reactions
QUIZ TIME
• What change occurs during photosynthesis?
A. solar energy is converted to chemical energy
B. kinetic energy is converted to chemical energy
C. chemical energy is converted to radiant energy
D. water is converted to chemical energy
ANSWER
•A. solar energy is
converted to chemical
energy
Cuticle
Epidermis
Guard cells
Palisade
Phloem
Xylem
Spongy
Mesophyll
Stomata
Bundle Sheath
A=cuticle
B=Upper epidermis
C=Vein
D=Phloem
E=xylem
F=Palisade layer
G=spongy layer
H=guard cell
I=stomata
QUIZ TIME
• The overall source of energy for
photosynthesis is:
• A. energy from the sun
• B. energy from ATP
• C. energy when oxygen is
produced
ANSWER
•A. energy from the sun
QUIZ TIME
• What three events occur during
the light reactions of
photosynthesis?
• Forming ATP
• NADP+ to NADPH
• Fixing CO2
• Releasing O2
ANSWER
• Forming ATP
• NADP+ to NADPH
• Releasing O2
QUIZ TIME
• Which of the following does not
happen in photosystem I?
• ATP is produced
• electron transport in the thylakoid
membranes
• light energy is used
• NADPH is formed
HINT
ANSWER (which is NOT)
• NADPH is formed
QUIZ TIME
• Where does the Calvin Cycle take
place?
• Thylakoid membranes of chloroplasts
• Stroma of chloroplasts
• Matrix of mitochondria
• Inner membrane of mitochondria
ANSWER
•Stroma of chloroplasts
QUIZ TIME
• What is the name of the
enzyme that causes CO2 to
form glucose?
• ATPase
• glucosease
• rubisco
ANSWER
•rubisco
QUIZ TIME
• What two high energy compounds
are required for this reaction?
• ATP
• NADH
• NADPH
• ADP
• FADH
ANSWER
•ATP and NADPH
QUIZ TIME
• What is the name of the process in
which carbon dioxide is made into
glucose?
• Krebs cycle
• Calvin cycle
• Einstein cycle
ANSWER
• CALVIN CYCLE
• (or sometimes the Calvin-Bensen
Cycle)
QUIZ TIME
• Which does NOT happen in the
Dark Reaction:
• using ATP
• using NADPH
• using Carbon Dioxide
• making water
ANSWER
• MAKING WATER
QUIZ TIME
• What are the products of the dark
reaction?
• ATP
• ADP
• glucose
• CO2
• NADP+
ANSWER
• ADP
• NADP+
• glucose
QUIZ TIME
• The reason why ADP + P form ATP in thylakoid
membranes is…
A movement of electrons between photosystem II
and photosystem I.
B oxidation of water
C oxidation of NADPH
D absorption of photons by chloroplast pigments
E higher concentration of H+ inside versus outside
the thylakoid membranes
ANSWER
• a higher concentration of H+
ions inside vs. outside the
thylakoid membranes
QUIZ TIME
• During photosynthetic electron transport, the interior
compartment of the thylakoid membranes becomes:
• A. more concentrated with ATP
• B. more concentrated with H+ ions
• C. less concentrated with H+ ions
ANSWER
• More concentrated with H+ ions
QUIZ TIME
• The overall source of energy for photosynthesis is:
• A. energy from the sun
• B. energy from ATP
• C. energy when oxygen is produced
ANSWER
• A. energy from the sun
QUIZ TIME
• What three events occur during
the light reactions of
photosynthesis?
• Forming ATP
• NADP+ to NADPH
• Fixing CO2
• Releasing O2
ANSWER
• Forming ATP
• NADP+ to NADPH
• Releasing O2
QUIZ TIME
• What is the name of the
process in which carbon
dioxide is made into glucose?
• Krebs cycle
• Calvin cycle
• Einstein cycle
ANSWER
• CALVIN CYCLE
• (or sometimes the Calvin-Bensen
Cycle)