Photosynthesis PPT
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This PowerPoint was revised June 24, 2008.
There is a TEKS Photosynthesis Notes
handout to accompany this PPT. (This is
the same handout for SM as well.) Review
it for possible use in other Biology courses.
There is repetition in this PPT used as a
learning strategy.
The notes section contains guides for
discussion.
PPT is 27 slides long.
Photosynthesis
What is the ultimate
source of all energy?
How does the energy get
from the sun into the foods
we eat?
ener
ene
rgy
gy
Why do we see colors?
 The
sun sends downs little
packets of light energy called:
PHOTONS
 Photons
group together in waves
 The waves have different lengths
 Each “wavelength” presents
itself as a color
Photons
Wavelengths
Why do we see colors?

Pigments absorb wavelengths of
light. The wavelengths not absorbed
are reflected. The colors we see are
the reflected wavelengths.
yellow
blue
red
green
orange
Why do we see colors?
 What
color is chlorophyll?
The plant pigment
chlorophyll reflects light in
these wavelengths.
The plant pigment chlorophyll absorbs the red and
blue colors of light so these colors are not seen.

What colors of light would a plant with purple
leaves absorb?
What colors are being absorbed and
what colors are being reflected?
Flowers from Clip Art
Chloroplast Structure

Chlorophyll pigments are in
structures called chloroplasts.
Disks called GRANA contain the pigment
CHLOROPHYLL.
The liquid portion of a chloroplast is the
STROMA
Where do
we find
chloroplasts?
Cross-section of a Leaf
 Chloroplasts
are found in cells of
leaves.
Cells containing chloroplast
with chlorophyll inside
stoma (stomata)
Review
1.
2.
3.
4.
What is the ultimate source of
all energy?
In what form does light energy
come to the earth?
What compounds absorbs
wavelengths?
How do we see colors?
Review
1.
2.
3.
4.
Which compound reflects the
green wavelengths thereby
making plants green?
Where would we find this
compound?
Where in a leaf do we find
pigments?
What are the small openings in
leaves for gas exchange called?
How do Plants Make Food?
 What
process captures the light
energy and uses it to make
food?
OVERVIEW OF
PHOTOSYNTHESIS
SUNLIGHT PROVIDES
THE ENERGY
overview
of photosynthesis
FOR PHOTOSYNTHESIS
light
carbon
dioxide
SUNLIGHT CAPTURED
BY CHLOROPHYLL
oxygen
carbohydrates
water
PLANTS TAKE IN
CO2 AND H2O
PLANTS MAKE GLUCOSE
AND OXYGEN
Photosynthesis
 What
is photosynthesis?
 Photosynthesis is the process
by which:
light
TAKE IN
AND USING
water
carbon dioxide
PLANTS
(producers)
chlorophyll
MAKE
oxygen
glucose
Photosynthesis
2
Phases:
 Light reactions
 Dark reactions (aka Calvin cycle)
Light Reaction
Dark Reaction
Who was Calvin anyway?

A member of the faculty
at UC Berkeley since
1937, Melvin Calvin
received the 1961 Nobel
prize in chemistry for
identifying the path of
carbon in
photosynthesis.
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The cycle of reactions in the dark phase
of photosynthesis was named after him
for his work in identifying the processes
taking place.
Photosynthesis
 Light
reaction:
 Occurs in the grana

Must have light
light
LIGHT
Light REACTION
Reaction
grana
(chlorophyll)
Dark Reaction
Photosynthesis
 Dark
reactions (aka Calvin cycle):
 Occurs in the stroma
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Occurs in the light and dark
Light Reaction
DARK
Dark REACTION
Reaction
stroma
(liquid)
Step 1: Light Reactions
O2isiskept
light
water
H
energy
released
is split
for the
by
reacts
the
dark
light
reaction
with
energy
the
chlorophyll
O2
O2
EN
ER
GY
H2 O
O2
O
O2
O2
H H H2
How does
the O2 leave
the leaf?
Step 1: Light Reactions
 In
GY
ER
EN
H2 O
the early 1600’s
Van Helmont did an
experiment that
showed plants get
vital growth
substances from
water.
Step 2: Dark Reactions
 AKA:
CALVIN CYCLE
glucose
H
CO
the
from
enters
the
is the
water
theHproduct
and
splitCO
in2
2reactants
the
light reaction is
chloroplast
combine
present
CO2
H H

CO2
H + CO2
COdoes
How
CO2
2
CO
enter
2 the plant?
C6H12O6
Other carbohydrates besides glucose
may be made in photosynthesis
Photosynthesis Review
Light reactions: H2O split into H2 + O

Dark reactions: H + CO2 = C6H12O6
O
2
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Light Reaction
Dark Reaction
2
chlorophyll
CO
H2O
C6H12O6
Photosynthesis Formula
How would this be written as a
chemical equation?
 What goes in? (the reactants)
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What comes out? (the products)
CO2
C6H12O6
O2
O
2
H2O
chlorophyll
Dark Reaction C6H12O6
2
Light Reaction
CO
H2O
Photosynthesis Formula
What’s wrong with this equation?
 The number of atoms is not equal on
both sides of the equation.

one carbon
atom reactant
6 H2O
6 CO2
6 carbon
atoms product
(1) C6H12O6
6 O2

Balance the equation so that the
number of atoms of each element is
equal on both sides.
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Now balance it as if TWO glucose
molecules were being produced.
TRY THIS!
 Think-Pair-Share
Analyze the relationship between
photosynthesis, biogeochemical
cycles, and food chains.
Photosynthesis Review
 What
goes in? (the reactants)
 What comes out? (the products)
chlorophyll
6O2 + C6H12O6
O
2
6CO2 + 6H2O
light
chlorophyll
Dark Reaction C6H12O6
2
Light Reaction
CO
H2O
Work Cited
Melvin Calvin picture. Online
image
http://www.lbl.gov/ScienceArticles/Archive/Melvin-Calvinobit.html
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