Bellwork:
What do you know
about photosynthesis?
Photo-synthesis
means "putting together with light."
6CO2
+
6H2O (+ light energy)
----->
C6H12O6
+ 6O2
Respiration
C6H12O6 +
6O2
-----> 6CO2
+ 6H2O
+ Energy (ATP)
Photosynthesis-starts the ecological food webs!
What is photosynthesis?
A
chemical reaction in which
light energy is converted to
chemical energy in the form of
glucose.
 It is how the energy in sunlight
becomes usable to living things.
Why is it so important?
Two big reasons:
1. One product is glucose (sugar),
which provides the basis for most
food chains.
2. The second product is oxygen which
is needed by aerobic organisms
(require oxygen) for survival.
Photosynthesis
sunlight
Carbon dioxide + water
absorbed by chlorophyll
glucose + oxygen
6CO2 + 6H2O + energy  C6H12O6 + 6O2
As can be seen from the equation for photosynthesis, the
wood, bark, and root came from water and carbon
dioxide.
Where does
photosynthesis occur?
 Most
photosynthesis occurs
in the oceans, the oceans
occupy (70%) of the
earth's surface!
In terms of organisms,
photosynthesis occurs in
autotrophs that contain the
green pigment chlorophyll.
Review:
What is an autotroph?
 Multicellular
level:
photosynthesis occurs in the
leaves of plants.
 Cellular
level: the reactions
for photosynthesis occur in
the chloroplasts of
eukaryotes and in the
cytoplasm of prokaryotes.
Plant leaves have many types of cells!
Chloroplasts make the sugars!
Plants
Leaves are green
because they
contain
the pigment:
chlorophyll
Why do leaves
have a broad
surface area?
"Thanks for the Glucose!"
PHOTOSYNTHESIS
• Why do we see green?
• Green color from white light
reflected NOT absorbed
• Chloroplast: organelle
responsible for photosynthesis
• Chlorophyll: located within
Chloroplast
• Green pigment
Plant Cells
The photograph below is an elodea leaf X 400.
Individual cells are clearly visible. The tiny
green structures within the cells are
chloroplasts
this is where
photosynthesis
happens.
What raw materials
are needed?
Chlorophyll
Sunlight
Water
Carbon
dioxide
Biochemical Pathway
Photosynthesis
is a
series of two reactions
The products from the
st
1 rxn are used in the
2nd
PHOTOSYNTHESIS
• 2 Phases
• Light-dependent reaction
• Light-independent reaction
• Light-dependent: converts light energy into
chemical energy; produces ATP molecules to
be used to fuel light-independent reaction
• Light-independent: uses ATP produced to
make simple sugars.
Summary of
Photosynthesis
carbon dioxide + water + light energy --> glucose + oxygen + water
As a chemical formula:
CO2 + H2O + light energy
---> C6H12O6 + O2 + H2O
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Extra Tidbits
 Important
part of OxygenCarbon Dioxide Cycle.
– pumps out oxygen
– Removes CO2 from atmosphere
of CO2 linked with ↑
global temp (think "Global
Warming").
 ↑levels
Chloroplasts
½ of the chemistry occurs in a
liquid inside the chloroplasts
called STROMA
½ of photosynthesis occurs in
stacks of membranes inside
the chloroplast called GRANA.
Chlorophyll
 Green
pigment, which
absorbs sunlight.
 2 types of chlorophyll
– chlorophyll a
– chlorophyll b
 Chlorophyll
a is the main,
b is an accessory
Chemical Reaction
Occurs in two phases.
Capture Energy
 #1 is called the "light
reactions". It requires light!
Convert Energy to Food
 #2 is called "carbon fixation" or
the "dark reactions".
Aka Calvin Cycle
It does not require light.
Start with CO2 End with Glucose
Photosynthesis
EQUATION FOR
PHOTOSYNTHESIS
WATER
6CO2 + 6H2O +ENERGY
CARBON
DIOXIDE
OXYGEN
C6H12O6 + 6O2
GLUCOSE
Back to the Chloroplast
 The
light reactions occur in
the grana, which contain the
chlorophyll for absorbing
light.
 The
dark reactions occur in
the stroma.
Detailed Light Reactions
 The
light reactions use light &
water, & produce the oxygen
"waste product".
 The
light energy is used to split
the water molecule (photolysis),
which produces e-’s. H+ & Oions. The oxygen is released
from the plant into the air.
 ATP
& NADPH2 are
energy molecules.
They will be used up
during the dark
reactions, as will the H+
ions.
Electron Transport

1.
2.
CONVERTS to useable Energy
Light excites the electrons
E-’s leave chlorophyll a and go
to the primary electron
acceptor (PEA) (in thylakoid
membrane)
Sun
Light energy transfers to chlorophyll.
• At each step
along the
transport chain,
the electrons
lose energy.
Chlorophyll passes energy down through the
electron transport chain.
Energized electrons provide energy that
splits
H2 O
H+
NADP+
oxygen
released
to ADP
bonds P
forming
ATP
NADPH
for the use in
light-independent reactions
3. PEA then donates the e’s
to other molecules which
pass them on over and
over. (electron transport
chain)
4. E’s join with a proton and
NADP+ which forms
NADPH
Replacing the Electrons
 E-’s
are taken from the
chlorophyll to pass down
the ETC.
 They must be replaced to
be passed down again.
 E-’s accumulated during
photolysis are given to the
chlorophyll.
Photosynthesis Rap
Check it!
EQUATION FOR
PHOTOSYNTHESIS
WATER
6CO2 + 6H2O +ENERGY
CARBON
DIOXIDE
OXYGEN
C6H12O6 + 6O2
GLUCOSE
PHOTOSYNTHESIS
• What affects photosynthesis?
• Light intensity: as light increases, rate of
photosynthesis _____________________
PHOTOSYNTHESIS
• What affects photosynthesis?
• Carbon Dioxide: As CO2 increases, rate of
photosynthesis _________________
PHOTOSYNTHESIS
• What affects photosynthesis?
• Temperature:
• Temperature Low = Rate of photosynthesis low
• Temperature Increases = Rate of photosynthesis increases
• If temperature too hot, rate drops
Chlorophyll: A Light Absorbing Pigment
The Solar Panel Chemical!
Photosynthesis
Glucose provides the energy and
carbon needed to make other
plant materials like wax and
proteins.
Oxygen and Sugar!
• In plants and simple animals, waste products are removed
by diffusion. Plants, for example, excrete O2, a product of
photosynthesis.
PHOTOSYNTHESIS
• How did we get O2 as a byproduct?!
• Photolysis: replaces lost electrons by splitting
water
Check it!
1. The process that uses the sun’s energy to
make simple sugars is _____________.
A.
B.
C.
D.
Cellular respiration
Glycolysis
Photosynthesis
Photolysis
Check it!
2. The function accomplished by the lightdependent reactions is ______________.
A.
B.
C.
D.
Energy storage
Sugar production
Carbon fixation
Conversion of sugar