PHOTOSYNTHESIS

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Phytochemistry Part 5

• PHOTOSYNTHESIS

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BASIC GOAL
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Figure 7.1 Freeman, BIOLOGICAL SCIENCE 103
textbook
4
Figure 7.1 Freeman, BIOLOGICAL SCIENCE 103
textbook
The overall reaction in photosynthesis
Light energy
Photosynthesis
O2

H2O
CO2


(C H2O)
Twocomponents
Light-dependent reactions
Light-independent reactions
Chemical energy (ATP, NADPH)
Light energy
Chemical energy (ATP, NADPH)
Chemical energy (C H2O)
O2
H2O
CO2
5
Figure 7.10a
In the Z scheme, electrons flow from water to
NADPH.
Higher
4e
Pheophytin
P680
2 NADP 2H
4e
PQ
Cytochromecomplex
Photon
Ferredoxin
Energy of electron
Photon
Pc
2 NADPH
ATP
produced via protonmotive force
P700
P700
P680
Photosystem I
P680
Photosystem II
4e
Lower
2H2O
4H O2
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Figure 6.12
ELECTRON TRANSPORT CHAIN
Inter- membrane space
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Complex l
Inner membrane
Q
Cyt c
Complex lll
Q
Complex ll
FAD
Complex lV
NADH
H
H
FADH2
Mito- chondrial matrix
NAD
H
2e- 2H 1/2 O2
H2O
Almost exactly the same as mitochondrial electron
transport in cellular respiration
7
Figure 6.13c
THE STRUCTURE OF ATP SYNTHASE
H
H
H
Intermembrane space
H
H
FO unit
Mitochondrial matrix
Rod
H
F1 unit
ADP Pi
ATP
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Figure 7.2a
Freeman, BIOLOGICAL SCIENCE
103 textbook
Leaves contain millions of chloroplasts
Leaf cross-section
Cells containing chloroplasts
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Figure 7.2b
Freeman, BIOLOGICAL SCIENCE 103
textbook
Chloroplasts are highly structured, membrane-rich
organelles.
Outermembrane
Innermembrane
Thylakoids
Granum
Stroma
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Figure 7.2c
Freeman, BIOLOGICAL SCIENCE

103 textbook
Photosynthetic bacteria have extensive internal
membranes too.
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Figure 7.11
H
H
Stroma
Photo- system II
Found in membrane facing inside of grana
H
Photo- system I
Found in membrane facing stroma
ATP synthase
H
Cytochrome complex
Equally common in both types of membrane
Granum
H
H
H
Stroma
H
H
H
H
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Figure 7.8a
In photosystem II, excited electrons feed
an electron transport chain.
Higher
Pheophytin
e
PQ
Electrontransport chain
Cytochromecomplex
Energy of electron
Photon
Freeman, BIOLOGICAL SCIENCE
103
textbook
Chlorophyll
Lower
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Figure 7.8b
Plastoquinone carries protons to the inside of
thylakoids, creating a proton motive force.
H
H
Photosystem II
Cytochromecomplex
2e
Pheophytin
PQ
2e
2e
Chlorophyll
PQ
H
H
H
Inside ofthylakoid(low pH)
H
H
H
H
H
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Figure 7.9
Higher
e
NADP H
Ferredoxin
Electrontransport chain
NADPH
Energy of electron
Photon
Chlorophyll
Lower
Freeman, BIOLOGICAL SCIENCE 103
textbook
15
Figure 7.10a
In the Z scheme, electrons flow from water to
NADPH.
Higher
4e
Pheophytin
P680
2 NADP 2H
4e
PQ
Cytochromecomplex
Photon
Ferredoxin
Energy of electron
Photon
Pc
2 NADPH
ATP
produced via protonmotive force
P700
P700
P680
Photosystem I
P680
Photosystem II
4e
Lower
2H2O
4H O2
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Figure 7.10b
In cyclic electron transport, which drives cyclic
photophosphorylation, photosystem I transfers
electrons to plastoquinone (PQ).
4e
Ferredoxin
PQ
Cytochromecomplex
Photon
Pc
ATP produced via protonmotive force
P700
Photosystem I
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Figure 6.13c
THE STRUCTURE OF ATP SYNTHASE
H
H
H
Intermembrane space
H
H
FO unit
Mitochondrial matrix
Rod
H
F1 unit
ADP Pi
ATP
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Figure 6.12
ELECTRON TRANSPORT CHAIN
Inter- membrane space
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Complex l
Inner membrane
Q
Cyt c
Complex lll
Q
Complex ll
FAD
Complex lV
NADH
H
H
FADH2
Mito- chondrial matrix
NAD
H
2e- 2H 1/2 O2
H2O
Almost exactly the same as mitochondrial electron
transport in cellular respiration
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Except 1. 2.
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Except 1. Electrons come from ______ 2.
Electrons go to ______ the final electron
acceptor is ______
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Figure 7.3
1013
Radiowaves
Visiblelight
1011
750
Lowerenergy
Higherwavelength
109
700
Micro-waves
107
105
Infrared
Wavelengths (nm)
600
103
Ultra-violet
101
500
10-1
X rays
10-3
Gammarays
Lowerwavelength
Higherenergy
400
10-5
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Figure 7.4a
ISOLATING PIGMENTS VIA PAPER CHROMATOGRAPHY
3. Separate pigments inone solvent.
4. Rotate paper and separatepigments insecond
solvent.
1. Grind leaf, add organic solvent. Pigment
moleculesmove from leaf tissue into solvent.
2. Spot pigments on filter paper.
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Figure 7.4b
A finished chromatogram
Carotene
Pheophytin
Chlorophyll a
Chlorophyll b
Carotenoids
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Figure 7.4c
Different pigments absorb different wavelengths
of light.
Chlorophyll a
Chlorophyll b
Carotenoids
Amount of light absorbed
400
600
500
700
Wavelength of light (nm)
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Figure 7.5a
?-carotene
CH3
CH3
H3C
CH
H3C
CH
CH3
CH3
HO
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Figure 7.5b
Chlorophyll a and b
CHO in chlorophyll b
CH3 in chlorophyll a
H2C
CH
H3C
CH2CH3
N
N
Mg
Ring structure in head(absorbs light)
N
N
H3C
CH3
CH2
O
COCH3
CH2
O
C
O
O
CH2
Tail
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Figure 7.6a
Electrons can be promoted to discrete high-energy
states.
e
Blue photons excite electrons to a higher energy
state
e
Red photons excite electrons to a high-energy
state
Photons
0
1
2
Energy state of electrons in chlorophyll
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Figure 7.6b
If the excited electron is not captured,
fluorescence occurs.
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Figure 7.6c
Chlorophyll molecules transmit energy from
excited electrons to a reaction center.
Photon
Reactioncenter
Photon
Chlorophyll molecules
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Figure 7.7
Both lights on
Relative rate of photosynthesis
Red light on
Far red light on
Time
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Figure 7.10a
In the Z scheme, electrons flow from water to
NADPH.
Higher
4e
Pheophytin
P680
2 NADP 2H
4e
PQ
Cytochromecomplex
Photon
Ferredoxin
Energy of electron
Photon
Pc
2 NADPH
ATP
produced via protonmotive force
P700
P700
P680
Photosystem I
P680
Photosystem II
4e
Lower
2H2O
4H O2
Freeman, BIOLOGICAL SCIENCE 103
textbook
32
Figure 7.11
H
H
Stroma
Photo- system II
Found in membrane facing inside of grana
H
Photo- system I
Found in membrane facing stroma
ATP synthase
H
Cytochrome complex
Equally common in both types of membrane
Granum
H
H
H
Stroma
H
H
H
H
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Figure 7.13
3 CO2
1. Carbondioxide isfixed
P
6 P
3 P
RuBP
3-phosphoglycerate
CALVIN CYCLE
6 ATP
2. 3-phospho- glycerate isreduced toG3P
3. RuBP isregeneratedfrom G3P
6 ADP
3 ADP
3 ATP
6 NADPH
6 NADP 6 Pi
6 P
5 G3P
G3P
1 G3P
Freeman, BIOLOGICAL SCIENCE 103
textbook
Glucose
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Figure 7.14
Rubisco
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Figure 7.15a
Leaf surfaces contain stomata
18 µm
Pore
Guard cells
Stoma
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Figure 7.15b
Carbon dioxide diffuse into leaves through stomata
H2O
H2O
Leaf cross-section
CO2
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Figure 7.16a
C4 plants sequester CO2 in certain cells
CO2
CO2 stored in one cell
Organicacid
CO2
CO2 used inadjacent cell
Calvin cycle
G3P
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Figure 7.16b
CAM plants sequester CO2 at night
CO2
CO2 storedat night
Organicacid
CO2
Calvincycle
CO2 usedduring the day
G3P
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Figure 7.17a
Sucrose
CH2OH
O
O
HOCH2
H
H
H
H
OH
HO
H
H
O
CH2OH
HO
H
OH
HO
H
Fructose subunit
Glucose subunit
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Figure 7.17b
Starch
CH2OH
CH2OH
CH2OH
O
O
O
H
H
H
H
H
H
Up to 1000or moremonomers
H
H
H
OH
H
H
OH
H
OH
O
O
O
O
OH
H
H
OH
OH
H
Glucosesubunit
Glucosesubunit
Glucosesubunit
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Figure 7.12a
IDENTIFYING INTERMEDIATES IN THE CALVIN CYCLE
X-ray film
14CO2
Chromatograph
1. Feed algaepulse of 14CO2
3. Separate molecules using paperchromatography
2. Wait for a definedinterval, then killcells
andhomogenize
4. Lay x-ray film onchromatograph tolocate
radioactivelabel
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Figure 7.12b
Evidence that 3-phosphoglycerate is the initial
product
3-phosphoglycerate
Compoundsproducedafter 5seconds
Compoundsproducedafter 60seconds
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Box 7.1, Figure 1
Proplastid
Chloroplast(photosynthesis)
Chromoplast(color)
Leucoplast(storage)
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BASIC GOAL
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