Photosynthesis
The Essence of Photosynthesis
• 1. Photosynthesis
• • energy from sunlight is converted into
chemical bond energy in the form of
carbohydrates
• 2. Summary equation for photosynthesis
The Essence of Photosynthesis cont.
• 3. Principle ingredients
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a. Carbon dioxide (CO2)
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b. Water
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c. Light
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d. Chlorophyll
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1) Several types
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2) All magnesium containing molecules
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3) Light harvesting complex called a
photosynthetic unit
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• 250-400 pigment molecules
The Essence of Photosynthesis cont.
• 3. Principle ingredients
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a. Carbon dioxide (CO2)
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b. Water
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c. Light
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d. Chlorophyll
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1) Several types
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2) All magnesium containing molecules
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3) Light harvesting complex called a
photosynthetic unit
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• 250-400 pigment molecules
Introduction to the Major Steps of
Photosynthesis
• 1. The Light-Dependent Reactions
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a. Reactions take place in thylakoid
membranes of chloroplast
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• light required
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b. Water split, producing hydrogen ions
and electrons, O2 gas released
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c. ATP created
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d. NADPH + H+ created
Introduction to the Major Steps of
Photosynthesis
Introduction to the Major Steps of
Photosynthesis
• 2. The Light-Independent Reactions (Calvin
cycle)
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a. Reactions take place in stroma of
chloroplast
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• light not required, hence "dark" reactions
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b. Calvin cycle
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1) Carbon dioxide from air combined with
5-carbon sugar
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2) Glucose formed through several
reaction steps
Introduction to the Major Steps of
Photosynthesis
• Label the components of the chloroplast and what they
do.
• Grana – light reaction
• Stroma – dark reaction
• Light trapping system
– E trapped and guided down to chloroplast
– 2 main kinds of chlorophyll: a, and b
– All light energy is transported to chlorophyll a which does
the task.
• B to a
• C to a
• Other pigments to a
spectrum
• Leaves absorbe the red and blue end of the
spectrum. That is why leaves look green.
• Accessory pigments to trap light E
• Xanthophylls – yellow antioxidant
• Carotene – orange antioxidant
A Closer Look at Photosynthesis
• 1. Historical perspective
• 2. The Light-Dependent Reactions
Reexamined
• a. Nature of light
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1) Wave and particle theory of light
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2) Photoelectric effect
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3) Photons
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• discrete packets of light energy
A Closer Look at Photosynthesis cont.
• b. Chlorophyll pigments
• • each pigment has typical absorption spectrum
• c. Consequences of light absorption by
chlorophyll
• 1) Emit light immediately (fluorescence)
• 2) Emit light after a delay (phosphorescence)
• 3) Absorbed energy converted to heat
• 4) Absorbed energy converted and stored in
chemical bond energy (photosynthesis)
A Closer Look at Photosynthesis cont.
• d. Photosystem I contains
• 1) 200 or more chlorophyll a molecules
2) Small amount of chlorophyll b
• 3) Carotenoid pigment with protein attached
• 4) Special reaction-center molecule of
chlorophyll a called P700
• 5) Iron-sulfur proteins (electron acceptors)
A Closer Look at Photosynthesis cont.
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e. Photosystem II contains
1) Chlorophyll a molecules
2) ß-carotene pigments attached to protein
3) Small amount of chlorophyll b
4) Special reaction-center molecule of chlorophyll a
called P680
5) Primary electron acceptor molecule called
pheophytin
F. Photolysis
g. Photophosphorylation
h. Chemiosmosis
A Closer Look at Photosynthesis cont.
• 3. The Light-Independent Reactions Reexamined
• a. The Calvin cycle (3-carbon pathway)
• b. Photorespiration
• c. The 4-carbon pathway
• d. CAM photosynthesis
• 4. Other Significant Processes that Occur in
Chloroplasts
The Essence of Respiration
• 1. Respiration defined
• • energy releasing process where simple
sugars are broken down during a series of
stages controlled by enzymes
• 2. Summary equation for respiration
• 3. Anaerobic respiration and fermentation
Introduction to the Major Steps of
Respiration
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1.
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a.
b.
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4.
a.
b.
c.
Glycolysis
Aerobic respiration
The Citric Acid (Krebs) Cycle
The Electron transport chain
Anaerobic respiration and fermentation
Factors affecting the rate of respiration
Temperature
Water
Oxygen
A Closer Look at Respiration
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1. Glycolysis re-examined
a. Phosphorylation
b. Sugar cleavage
2. Transition Step to the Citric Acid (Krebs) Cycle
a. Pyruvic acid
b. Acetyl CoA
3. The Krebs cycle re-examined
4. Electron transport and oxidative
phosphorylation
• END