Photosynthesis
4.1 How do living things get ATP?
• ATP is the energy carrier in living things – it is
usable energy for the cell (chemical potential
energy).
• ATP stands for Adenosine triphosphate.
• Living things get ATP from breaking down carbon
based molecules. (carbohydrates & lipids)
Starch molecule
Glucose molecule
This is how it works
phosphate removed
PHOTOSYNTHESIS
• Autotrophic Process: Plants and some bacteria
(producers) take light energy from the sun and
store it as chemical energy (glucose)
• Energy is stored as carbohydrate (CPE) in
seeds and bulbs
• Equation:
6CO2 + 6H2O (+ sunlight)  C6H12O6 + 6O2
PHOTOSYNTHESIS
• Absorbing Light Energy
• Pigments: Absorb different colors of white (visible)
light (ROY G BIV)
• Main pigment: Chlorophyll a
• Accessory pigments: Chlorophyll b and Carotenoids
• These pigments absorb all wavelengths (light) BUT
green
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
STOP & REVIEW
• What are the three inputs (reactants) required for photosynthesis to begin?
(use chemical formulas when possible)?
• 1.Light
• 2.6H2O
• 3.6CO2
• What are the two outputs (products) of photosynthesis?
• 1.6O2
• 2.C6H12O6
• In what organelle does photosynthesis take place?
• 1.chloroplast
• What pigment is contained in that organelle?
• 1.chlorophyll
• What are the stack like structures called in that organelle?
• 1.thlakoids
• What is the liquid part called inside that organelle?
• 1.stroma
PHOTOSYNTHESIS
• Photosynthesis has 2 phases:
• Light-dependent reaction: converts light
energy into chemical energy; produces ATP &
NADPH (energy carriers) to be used to fuel
light-independent reaction. Steps: Photosystem
II, ETC, Photosystem I.
• Light-independent reaction: uses ATP &
NADPH produced in light-dependent reaction
and fixes carbon from CO2 to make simple
sugars (glucose).
PHOTOSYNTHESIS
• Light-dependent reaction (LIGHT Reaction)
• 1. Requires light
• 2. Occurs in chloroplast (in thylakoids)
• Thylakoids: membrane enclosed compartments;
membrane contains chlorophyll & other light-absorbing
molecules.
• Granum (grana): stacks of thylakoids
• 3. Chlorophyll (thylakoid) traps energy from light
• 4. Light excites electron (e-)
• Kicks e- out of chlorophyll to an electron transport chain
• Electron transport chain: series of proteins in thylakoid
membrane (like a bucket brigade)
PHOTOSYNTHESIS
• 5. Energy “lost” along electron transport chain
• 6. “Lost” energy used to recharge ATP from ADP
• ATP synthase: a complex enzyme that makes ATP by
adding phosphate groups to ADP.
• 7. NADPH produced from e- transport chain
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NADP+ accepts electrons to become NADPH
Stores energy until transfer to stroma
Plays important role in light-independent reaction
Has ability to donate e-
• Total byproducts: ATP, NADPH, O2
PHOTOSYNTHESIS
• How did we get O2 as a byproduct?!
• Photolysis: replaces electrons lost from chlorophyll
by splitting water into oxygen, hydrogen ions, and
electrons.
• Oxygen is released during the light dependent
reaction
• At each step
along the
transport chain,
the electrons
lose energy.
This energy is
used to make
NADPH and
ATP for the
light
independent
reactions.
Light energy transfers to chlorophyll.
Chlorophyll passes energy down through the
electron transport chain.
Energized electrons provide energy that
to ADP
bonds P
splits
H2 O
H+
NADP+
oxygen
released
NADPH
for the use in
light-independent reactions
forming
ATP
STOP & REVIEW LIGHT
DEPENDENT REACTION
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What is the first thing that is required to start this part of the reaction?
1.Light
Where does this part of the reaction occur?
1.Chloroplast - thylakoids
What traps the energy from the light?
1.Chlorophyll
The light excites _________ and kicks them out of chlorophyll to an
___________ __________ ________?
1. Electrons, Electron Transport Chain
The energy that is lost along that chain is used to recharge ADP into ______
and NADP into ________.
1. ATP and NADPH
What is made at the end of this reaction that is used to run the next reaction?
1. ATP, NADPH
What is made and released during this part of the reaction?
1. Oxygen
PHOTOSYNTHESIS
• Light-independent reaction (Dark Reaction,
Calvin Cycle)
• 1. Does not require light
• 2. Occurs in stroma of chloroplasts
• Stroma: The fluid outside of the thylakoids.
• 3. Requires CO2
• 4. Uses ATP and NADPH as fuel to run
• 5. Makes glucose (sugar) from CO2 and Hydrogen
• End Products: glucose, NADP+, ADP
• Overall chemical equation of
photosynthesis:
• 6CO2 + 6H2OC6H12O6 + 6O2
• Overall energy transformation of
photosynthesis:
• Light/Radiant energyChemical potential
energy
STOP & REVIEW (DARK
REACTION)
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1. Why is this part called the dark reaction?
1.It does not require light.
2. What are the other names for this part of the reaction?
2. Calvin Cycle, Light Independent
3. Where does this part of the reaction occur?
3.Stroma
4. What is needed from the reactants to start the dark reaction?
4.Carbon dioxide
5. What is needed from the first reaction to run this part of the
reaction?
5.ATP, NADPH
6. What is made in the dark reaction using carbon dioxide and
hydrogen?
6.Glucose
7. What are the final products of the dark reaction?
7.Glucose, ADP, NADP
PHOTOSYNTHESIS
• What affects photosynthesis?
• Light intensity: as light increases, rate of
photosynthesis increases
PHOTOSYNTHESIS
• What affects photosynthesis?
• Carbon Dioxide: As CO2 increases, rate of
photosynthesis increases
PHOTOSYNTHESIS
• What affects photosynthesis?
• Temperature:
• Temperature Low = Rate of photosynthesis low
• Temperature Increases = Rate of photosynthesis increases
• If temperature too hot, rate drops
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