Fig. 10.1
Outline - Photosynthesis
Photosynthesis
1. An Overview of Photosynthesis & Respiration
2. Autotrophs, photoautotrophs, and producers
3. Electromagnetic Spectrum & light energy
4. Chloroplast structure and location in a leaf
5. Photosynthetic pigments: Chlorophylls & Carotenoids
6. Chemical Reactions of Photosynthesis
Light Harvesting
Sugar Building
8. Photosynthesis Review
Overview of Photosynthesis & Respiration
Photosynthesis Equation
Reduction
6 CO2 + 6 H2O
C6H12O6 + 6 O2
Oxidation
• Photosynthesis is a redox process
• H2O is oxidized and CO2 is reduced
1
Autotrophs & Photoautotrophs are Producers
Photosynthesis Overview
Photoautotrophs - sun
Chemoautotrophs - inorganic sources
NH3, H2S and Sulfur
Photosynthesis has two main stages:
Light-dependent reactions
-capture energy from sunlight
-make ATP and reduce NADP+ to NADPH
Photoautotrophs
Plants
Algae
Cyanobacteria
Light-independent reactions
or carbon fixation reactions
-use ATP and NADPH to synthesize
organic molecules from CO2
Chemoautotrophs
Sulfolobus
Conditions: pH 1.0 at 95C
Habitat: Hot springs, mud pots
Oxidizes sulfur to sulfuric acid
5
Light Absorption During Photosynthesis
Electromagnetic Spectrum
W
h
it
e
Increasing
energy
0.1 nm
Increasing
wavelength
1 nm 10 nm 1000 nm 0.1 cm 1 cm
Gamma rays
X
UV
rays light
Infrared
Sun
1m
L
i
g
h
t
100 m
Radio waves
Visible light
400 nm
430 nm
500 nm
560 nm 600 nm
650 nm
740 nm
Pigments Æ absorb visible light
Absorption spectrum characteristic of each pigment
Defines range & efficiency of light absorption
2
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Absorption Spectrum of Photosynthetic Pigments
Chlorophyll a, Chlorophyll b & Carotenoids
Pigments of Photosynthesis
Amount of light absorption
Carotenoid
Chlorophyll a
Chlorophyll b
400
450
500
550
600
650
700
Wavelength (nm)
Plant Cell Chloroplasts
Chlorophyll a
Chlorophyll b
= green pigments
Carotenoids
= orange/yellow pigments
= accessory pigments
Chloroplast Structure
Thylakoid
Inner membrane
Outer membrane
Granum
Stroma
3
Fig. 10.2db (TEArt)
Photosynthesis Overview
H20
O2
Light
Harvesting
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Photosynthesis is Light
Harvesting & Sugar-Building
H20
Light
Harvesting
LightDependent
Reactions
Thylakoid
Photosystem
O2
Thylakoid
Light Harvesting
Sugar
Building
Sugar
Building
Stroma
Carbohydrate
CO2
Fig. 10.6a (TEArt)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Photosynthesis: Light Harvesting by Photosystems
Chlorophyll molecules
and Carotenoids
in light-harvesting
antenna complex
Thylakoid
membrane
Light
Independent
Reactions
Calvin Cycle
ADP
Stroma
ATP NADPH
NADP+
Sugar
Building
Carbohydrates
CO2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 10.10 (TEArt)
Photosynthesis: Light Harvesting by Photosystems
Sun
Reaction
center
Photon chlorophyll
e-
Electron
Acceptor
e-
Chlorophyll
molecules
Reaction Center Chlorophyll
Photosystem
4
Photosystem I Reduces NADP+
e-
Photosystem II Supplies Electrons to PSI
ePSII Reaction
Center
Photosystem I
Photosystem II
Water Splitting & Oxygen Production
Photosystem II Supplies Electrons to PSI
H+
e-
H+
eH2O
O
O
O2
Photosystem II
5
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Fig. 10.6b (TEArt)
Photosystem II Supplies Electrons to PSI
Thylakoid Structure
H+
Thylakoid
H+
H+
H+ H+
H+
H+
e-
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 10.16b (TEArt)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 10.14 (TEArt)
Photosynthesis: Light Harvesting by Photosystems
Chemiosomosis & ATP Synthesis in Chloroplasts
Excited
reaction
center
H+
Photon
H+
Stroma
ADP
ATP
Ferredoxin
e–
Fd
Stroma
eH2O
Q
Thylakoid
space
1
_
2H+
2 02
Photosystem II
H+
H+
H+
H+
Energy of electrons
Plastoquinone
e–
Reaction
center
e–
Photon
P680
H+
b6-f complex
NADP
reductase
e–
NADP+ + H+
Q
b6-f
Plastocyanin Reaction
complex
center
Photon
pC
+
Water- H
P700
splitting
enzyme
H2O
2H+ +
NADPH
1
__
O2
2
Photosystem I
NADP reductase
ATP synthase
Photosystem II
b6-f complex
6
Light-Dependent Reactions
Light Reactions Mechanical Analogy
H2O provides electrons
electron transport chain
reduce NADPH
e–
ATP synthesized
Oxygen released
e–
Light-dependent reactions occur in 4 stages:
1. Primary photoevent –photon of light is
captured by a pigment molecule
ATP
e–
e–
–
e– e
NADPH
Photon
4. Chemiosmosis – produces ATP
H2O
Figure 7.8B
O2
3. Electron transport – electrons move through
membrane carriers to reduce NADP+
e–
Photon
2. Charge separation – energy is transferred to
the reaction center; an excited electron is
transferred to an acceptor molecule
e-
Photosystem II
Photosystem I
Consequences of Light Harvesting Reactions
26
Sugar-Building & the Calvin Cycle
1. NADP Æ reduced to NADPH
2. ATP synthesized by chemiosmosis
And…
3. Oxygen is released
4. H2O provides electrons for electron transport chain
7
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Fig. 10.17 (TEArt)
Sugar Building – The Calvin Cycle
1
2
CO2
3
3-phospho
glycerate
P
Carbon Fixation Reactions
Calvin cycle
RuBP
3-phospho
glycerate
RuBP
carboxylase
enzyme
RuBP
ATP
NADPH
-biochemical pathway that allows for carbon fixation
-occurs in the stroma
Glyceraldehyde
3-phosphate
-uses ATP and NADPH as energy sources
Glyceraldehyde
3-phosphate
-incorporates CO2 into organic molecules
Glucose
Carbon Dioxide
Fixation
Regeneration
of RuBP
Carbon
Reduction
30
PHOTOSYNTHESIS REVIEW
Light
Global Connection Between Respiration & Photosynthesis
H2O Chloroplast CO2
NADP+
ADP
P
RUBP
Photosystem II
Thylakoid
membranes
CALVIN
CYCLE
Light
Reactions
Photosystem I
Stroma
ATP
NADPH
3-PGA
G3P
Cellular
respiration
Cellulose
Starch
O2
Sugars
Other organic
compounds
Figure 7.11
32
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
8
CAM Photosynthesis
Night
CO2
4-C compound
CO2
CO2
CALVIN
CYCLE
Day
3-C sugar
33
9