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5.2 Notes…continued
Analyze the function of electron transport
chains in the second stage of
photosynthesis.
Relate the Calvin cycle to carbon dioxide
fixation in the third stage of
photosynthesis.
Identify three environmental factors that
affect the rate of photosynthesis.
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Stage Two: Conversion of Light
Energy
 The
absorbed light energy in electrons is
used to make three different products…
ATP
 __________
O2
 __________
NADPH
 __________
 Since
these substances need light to be
produced, stage two is referred to as the
light
dependent
____________
_________________
reactions
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Section 2 Photosynthesis
First an excited electron jumps
_______ to a nearby
molecule in the thylakoid membrane.
Then the electron is passed down a series of
molecules along the membrane called an
chain
electron
transport ____________
_____________
_______________
(ETC)
As electrons move down the molecules, they
release ____________…
energy
Similar to how a bucket brigade loses
water
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Chapter 5
Section 2 Photosynthesis
Electron Transport Chains of
Photosynthesis
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Chapter 5
Section 2 Photosynthesis
The first
electron
transport
chain lies
between the
two green
clusters
___________
of
pigment
molecules
• The first pigment cluster is called _________________
Photosystem II
(PSII) because it was the second one discovered
– It absorbs energy and releases an excited
electron
____________
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Chapter 5
Section 2 Photosynthesis
The excited
electron
jumps to the
next
molecule in
the electron
transport
chain,
releasing
energy
____________
• This energy is used by a membrane pump that pumps
into
___________________
ions _______
the thylakoid
hydrogen
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Chapter 5
Section 2 Photosynthesis
This creates
a
build
__________
up of
____
hydrogen
ions inside
the
thylakoid
This concentration gradient causes hydrogen ions to
out of
________________
through a transport protein _____
diffuse
stroma
the thylakoid into the ___________
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Chapter 5
Section 2 Photosynthesis
The flow of
hydrogen
ions causes
the transport
protein to
spin
__________
force
• The spinning action creates a __________
that binds a
phosphate group to ADP, producing _______
ATP
• Since this transport protein produces ATP, it is called
ATP synthetase / ATP Synthase
_____________________
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Chapter 5
Section 2 Photosynthesis
The energy
released from
the electrons
also allows an
enzyme to split
water
a ______
molecule into
hydrogen
atoms and the
O2
gas ___
• Chlorophyll molecules replace their excited electrons
by taking an electron from hydrogen atoms, leaving
ions
them as _______.
This allows light energy to excite
another electron in PSII
___________
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Chapter 5
Section 2 Photosynthesis
The second
cluster of
pigments is
called
Photosystem I
______________
(PSI) because it
was the first one
discovered
• The original excited electron from ______
PSII is
eventually passed to PSI, where chlorophyll
excite
molecules will absorb light energy and __________
the electron again
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Chapter 5
Section 2 Photosynthesis
These excited
electrons move
second
down a ________
electron
transport chain,
releasing energy
hydrogen
• The released energy is used to bind a ___________
NADPH
ion to NADP+, which forms ___________
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Chapter 5
Section 2 Photosynthesis
carrier
NADPH is an electron ___________
that provides
the high-energy electrons needed to make
sugar
___________
in the third stage of photosynthesis
Review…
What three products are made during the lightdependent reactions?
ATP
O2
NADPH
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Chapter 5
Section 2 Photosynthesis
Stage Three: Formation of Organic Compounds
 In the third (final) stage of photosynthesis, carbon atoms from
carbon dioxide in the atmosphere are used to make
_________________
glucose in which
organic compounds, such as ______________,
chemical energy is stored.
 The transfer of carbon dioxide to organic compounds is called
fixation
carbon dioxide _______________
 These reactions do not require light energy, so stage three is
referred to as the light ____________________or
_____
independent
dark reactions
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Chapter 5
Section 2 Photosynthesis
Sugars are
formed in the
Calvin
________________
cycle which is
_______,
named after
Melvin
__________
Calvin the
__________,
scientist who
discovered it
***Occurs in the
stroma
____________
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Chapter 5
Section 2 Photosynthesis
3 CO2
First ____
molecules
are added to
3 5____
carbon
compounds
called
ribulose
____________
biphosphate
____________
RuBP
(_______)
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Chapter 5
Section 2 Photosynthesis
These form 3
unstable
6
___-carbon
compounds
that
immediately
6
split into ____
3-carbon
compounds
called
phosphoglyceric
____________
____________
acid (PGA)
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Chapter 5
Section 2 Photosynthesis
Next, the ATP
and NADPH
made during
light
the _________
reactions
energy
supply _______
6 3for ___
carbon
sugars, called
phosphoglycer____________
___________,
aldehyde
(PGAL)
to be made
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Chapter 5
Section 2 Photosynthesis
One PGAL is
used by the
plant to
synthesize
sugars
___________,w
hile the others
regenerate
RuBP, which
began the
cycle
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Chapter 5
Section 2 Photosynthesis
As shown in
the diagram,
RuBP needs
another
phosphate
before the
cycle can
begin again…
where does it
come from?
ATP
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Chapter 5
Section 2 Photosynthesis
What organic
compound
does a plant
need to make
for itself?
glucose
What is its
formula?
C6H12O6
How many
carbon atoms
does it contain?
6
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Chapter 5
Section 2 Photosynthesis
How many
carbons are
in the initial
sugar
produced?
3
So while this
diagram
shows 3 CO2
molecules,
photosynthesi
s really needs
6
_____
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 Fill
in the coefficients in the equation for
photosynthesis below…
6 CO2
__
light
6
+ __ H20 ------------ > C6H1206 +
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6 O2
__
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Chapter 5
Section 2 Photosynthesis
Photosynthesis is directly affected by various
environmental factors such as…
_____________________
Light intensity
_____________________
CO2 concentration
temperature
_____________________
The rate of photosynthesis will increase with light
intensity and CO2 concentration, until all of the
Calvin
pigments
_____________
are being used or the _________
cycle cannot process CO2 any faster
enzymes
Because photosynthesis involves ___________,
it is
efficient
most ___________
within a specific temperature
range
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Question 1
 In
what part of the chloroplast are the
electron transport chains located?
In the thylakoid membranes
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Question 2
 Which
of the following is not a product of
the light-dependent reactions?
A. O2
B. glucose
C. ATP
D. NADPH
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Question 3
 Which
molecule is necessary to start the
Calvin cycle?
A. O2
B. glucose
C. CO2
D. ADP
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Question 4
 What
two other names are used to
describe the Calvin cycle?
Light independent reactions
Dark reactions
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