Chapter 10: Photosynthesis
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Transcript of Chapter 10: Photosynthesis
Slide 1
Chapter 10:Chapter 10:
PhotosynthesisPhotosynthesis
Figure 10.2
(a) Plants(b) Multicellular
alga
(c) Unicellularprotists
(d) Cyanobacteria
(e) Purple sulfurbacteria
10 m
1 m
40 m
Slide 3
What we What we (should) already (should) already
know!know!
Sunlight energy
ECOSYSTEM
Photosynthesisin chloroplasts
GlucoseCO2
O2H2O
Cellular respirationin mitochondria
(for cellular work)
Heat energy
ATP
Slide 4
Plants are producersPlants are producers
• Autotrophs – make their own organic Autotrophs – make their own organic molecules from inorganic carbon (COmolecules from inorganic carbon (CO22))
• Photoautotrophs – use light to Photoautotrophs – use light to make organic moleculesmake organic molecules
• Heterotrophs - obtain organic molecules Heterotrophs - obtain organic molecules from another organismfrom another organism
• ConsumersConsumers
• DecomposersDecomposers
Figure 10.4a
Mesophyll
Leaf cross section
Chloroplasts Vein
Stomata
Chloroplast Mesophyllcell
CO2 O2
20 m
Leaf Leaf StructurStructur
ee
Figure 10.4b
Outermembrane
IntermembranespaceInnermembrane
1 m
Thylakoidspace
ThylakoidGranumStroma
Chloroplast
ChloroplasChloroplaststs
Figure 10.5
Reactants:
Products:
6 CO2
6 H2O 6 O2
12 H2O
C6H12O6
PhotosynthesisPhotosynthesis
Slide 8
Tracer ExperimentTracer Experiment
• Used radiolabeled oxygen atoms in the reactants Used radiolabeled oxygen atoms in the reactants to determine which contributed the O2 that is to determine which contributed the O2 that is released by plantsreleased by plants
• Could be from COCould be from CO22 or H or H22OO
Slide 9
Oxidation-Reduction Reactions Oxidation-Reduction Reactions (Redox)(Redox)• Occurs when electrons are moved from one Occurs when electrons are moved from one
molecule to anothermolecule to another
• The molecule that loses the The molecule that loses the electron(s) is OXIDIZED (called electron(s) is OXIDIZED (called oxidation)oxidation)
• The molecule that gains the The molecule that gains the electron(s) is REDUCED (called electron(s) is REDUCED (called reductions)reductions)
• They will always go togetherThey will always go together
• As electrons move, they gain potential As electrons move, they gain potential energy (in photosynthesis)energy (in photosynthesis)
• In photosynthesis, electrons move from In photosynthesis, electrons move from water to CO2, forming sugarswater to CO2, forming sugars
Figure 10.UN01
Energy 6 CO2 6 H2OC6 H12 O6 6 O2
becomes reduced
becomes oxidized
Photosynthesis is a Redox Photosynthesis is a Redox ReactionReaction
Figure 10.6-1
Light
LightReactions
Chloroplast
NADP
ADP
+ P i
H2O
Figure 10.6-2
Light
LightReactions
Chloroplast
ATP
NADPH
NADP
ADP
+ P i
H2O
O2
Figure 10.6-3
Light
LightReactions
CalvinCycle
Chloroplast
ATP
NADPH
NADP
ADP
+ P i
H2O CO2
O2
Figure 10.6-4
Light
LightReactions
CalvinCycle
Chloroplast
[CH2O](sugar)
ATP
NADPH
NADP
ADP
+ P i
H2O CO2
O2
Figure 10.7
Gammarays X-rays UV Infrared
Micro-waves
Radiowaves
Visible light
Shorter wavelength Longer wavelength
Lower energyHigher energy
380 450 500 550 600 650 700 750 nm
105 nm 103 nm 1 nm 103 nm 106 nm (109 nm) 103 m1 m
Ele
ctro
magneti
c Ele
ctro
magneti
c Spect
rum
Spect
rum
Figure 10.8
Chloroplast
LightReflectedlight
Absorbedlight
Transmittedlight
Granum
Chloroplasts absorb only certain Chloroplasts absorb only certain colorscolors
Figure 10.9
Whitelight
Refractingprism
Chlorophyllsolution
Photoelectrictube
Galvanometer
Slit moves topass lightof selectedwavelength.
Greenlight
High transmittance(low absorption):Chlorophyll absorbsvery little green light.
Bluelight
Low transmittance(high absorption):Chlorophyll absorbsmost blue light.
TECHNIQUE
Figure 10.10
(b) Action spectrum
(a) Absorptionspectra
Engelmann’sexperiment
(c)
Chloro-phyll a Chlorophyll b
Carotenoids
Wavelength of light (nm)
Ab
so
rpti
on
of
lig
ht
by
ch
loro
pla
st
pig
me
nts
Ra
te o
f p
ho
tos
yn
the
sis
(m
ea
su
red
by
O2
rele
as
e)
Aerobic bacteria
Filamentof alga
400 500 600 700
400 500 600 700
400 500 600 700
RESULTS
Slide 19
Pigments in chloroplastsPigments in chloroplasts
1.1. Chlorophyll Chlorophyll aa: absorbs blue-violet and : absorbs blue-violet and redred
2.2. Chlorophyll Chlorophyll bb: absorbs blue and : absorbs blue and orangeorange
3.3. Carotenoids: absorbs other Carotenoids: absorbs other wavelengthswavelengths
4.4. Other pigments: found in various Other pigments: found in various plantsplants
Figure 10.11
Hydrocarbon tail(H atoms not shown)
Porphyrin ring
CH3
CH3 in chlorophyll aCHO in chlorophyll b
Chlo
rophyll
Chlo
rophyll
Slide 21
““Excited” electronsExcited” electrons
• Ground state – where the electron is normallyGround state – where the electron is normally
• Excited state – where the electron is when it Excited state – where the electron is when it becomes excited (usually an energy level farther becomes excited (usually an energy level farther from the nucleus)from the nucleus)
• More unstableMore unstable
• More potential energyMore potential energy
Figure 10.12
Excitedstate
Heat
e
Photon(fluorescence)
Groundstate
PhotonChlorophyll
molecule
En
erg
y o
f el
ectr
on
(a) Excitation of isolated chlorophyll molecule (b) Fluorescence
““Falling” electrons release energyFalling” electrons release energy
Figure 10.13a
(a) How a photosystem harvests light
Th
ylak
oid
mem
bra
ne
PhotonPhotosystem STROMA
Light-harvestingcomplexes
Reaction-centercomplex
Primaryelectronacceptor
Transferof energy
Special pair ofchlorophyll amolecules
Pigmentmolecules
THYLAKOID SPACE(INTERIOR OF THYLAKOID)
e
Slide 24
PhotosystemsPhotosystems
There are two photsystems in plants:There are two photsystems in plants:
• Photosystem II (P680): reaction center Photosystem II (P680): reaction center chlorophyll a absorbs light at 680 nmchlorophyll a absorbs light at 680 nm
• Photosystem I (P700): reaction center Photosystem I (P700): reaction center chlorophyll a absorbs light at 700 nmchlorophyll a absorbs light at 700 nm
Slide 25
The Light ReactionsThe Light Reactions
• Sunlight used to make ATP and NADPH for the Sunlight used to make ATP and NADPH for the Calvin CycleCalvin Cycle
• Works by exciting electrons so that when they Works by exciting electrons so that when they “fall”:“fall”:
1. The energy can be captured to make ATP1. The energy can be captured to make ATP
2. The electrons can be placed on NADPH 2. The electrons can be placed on NADPH
Figure 10.14-1
Primaryacceptor
P680
Light
Pigmentmolecules
Photosystem II(PS II)
1
2e
Linear Electron FlowLinear Electron Flow
Figure 10.14-2
Primaryacceptor
H2O
O2
2 H
+1/2
P680
Light
Pigmentmolecules
Photosystem II(PS II)
1
2
3
e
e
e
Linear Electron Flow (cont.)Linear Electron Flow (cont.)
Figure 10.14-3
Cytochromecomplex
Primaryacceptor
H2O
O2
2 H
+1/2
P680
Light
Pigmentmolecules
Photosystem II(PS II)
Pq
Pc
ATP
1
2
3
5
Electron transport chaine
e
e
4
Linear Electron Flow (cont.)Linear Electron Flow (cont.)
Figure 10.14-4
Cytochromecomplex
Primaryacceptor
Primaryacceptor
H2O
O2
2 H
+1/2
P680
Light
Pigmentmolecules
Photosystem II(PS II)
Photosystem I(PS I)
Pq
Pc
ATP
1
2
3
5
6
Electron transport chain
P700
Light
e
e
4
e
e
Linear Electron Flow (cont.)Linear Electron Flow (cont.)
Figure 10.14-5
Cytochromecomplex
Primaryacceptor
Primaryacceptor
H2O
O2
2 H
+1/2
P680
Light
Pigmentmolecules
Photosystem II(PS II)
Photosystem I(PS I)
Pq
Pc
ATP
1
2
3
5
6
7
8
Electron transport chain
Electron
transport
chain
P700
Light
+ HNADP
NADPH
NADP
reductase
Fd
e
e
e
e
4
e
e
Linear Electron Flow (cont.)Linear Electron Flow (cont.)
Figure 10.15
Photosystem II Photosystem I
Millmakes
ATP
ATP
NADPH
e
e
e
ee
e
e
Ph
oto
n
Ph
oto
n
Figure 10.16
Photosystem I
Primaryacceptor
Cytochromecomplex
Fd
Pc
ATP
Primaryacceptor
Pq
Fd
NADPH
NADP
reductase
NADP
+ H
Photosystem II
Cyclic Electron FlowCyclic Electron Flow
Figure 10.17Mitochondrion Chloroplast
MITOCHONDRIONSTRUCTURE
CHLOROPLASTSTRUCTURE
Intermembranespace
Innermembrane
Matrix
Thylakoidspace
Thylakoidmembrane
Stroma
Electrontransport
chain
H Diffusion
ATPsynthase
H
ADP P iKey Higher [H ]
Lower [H ]
ATP
Figure 10.18
STROMA(low H concentration)
STROMA(low H concentration)
THYLAKOID SPACE(high H concentration)
Light
Photosystem II
Cytochromecomplex Photosystem I
Light
NADP
reductase
NADP + H
ToCalvinCycle
ATPsynthase
Thylakoidmembrane
2
1
3
NADPH
Fd
Pc
Pq
4 H+
4 H++2 H+
H+
ADP+P i
ATP
1/2
H2OO2
Chemiosmosis (…again)Chemiosmosis (…again)
Slide 35
PhotophosphorylatiPhotophosphorylation vs. Oxidative on vs. Oxidative PhosphorylationPhosphorylation
How are they different?:How are they different?:
1.1. Source of the Source of the electronselectrons
Photo ________Photo ________
Oxi __________Oxi __________
2.2. Source of the energySource of the energy
Photo Photo ________________
Oxi Oxi ____________________
3.3. Fate of the electronsFate of the electrons
Photo ________Photo ________
Oxi __________Oxi __________
Slide 36
Input
CO2
ATP
NADPH
CALVINCYCLE
Output: G3P
The The Calvin Calvin CycleCycle
Figure 10.19-1Input
3 (Entering oneat a time)
CO2
Phase 1: Carbon fixation
Rubisco
3 P P
P6
Short-livedintermediate
3-Phosphoglycerate3 P P
Ribulose bisphosphate(RuBP)
Figure 10.19-2Input
3 (Entering oneat a time)
CO2
Phase 1: Carbon fixation
Rubisco
3 P P
P6
Short-livedintermediate
3-Phosphoglycerate6
6 ADP
ATP
6 P P1,3-Bisphosphoglycerate
CalvinCycle
6 NADPH
6 NADP
6 P i
6 P
Phase 2: Reduction
Glyceraldehyde 3-phosphate(G3P)
3 P PRibulose bisphosphate
(RuBP)
1 PG3P
(a sugar)Output
Glucose andother organiccompounds
Figure 10.19-3Input
3 (Entering oneat a time)
CO2
Phase 1: Carbon fixation
Rubisco
3 P P
P6
Short-livedintermediate
3-Phosphoglycerate6
6 ADP
ATP
6 P P1,3-Bisphosphoglycerate
CalvinCycle
6 NADPH
6 NADP
6 P i
6 P
Phase 2: Reduction
Glyceraldehyde 3-phosphate(G3P)
P5G3P
ATP
3 ADP
Phase 3:Regeneration ofthe CO2 acceptor(RuBP)
3 P PRibulose bisphosphate
(RuBP)
1 PG3P
(a sugar)Output
Glucose andother organiccompounds
3
Slide 40Fig. 10-21
LightReactions:
Photosystem II Electron transport chain
Photosystem I Electron transport chain
CO2
NADP+
ADP
P i+
RuBP 3-Phosphoglycerate
CalvinCycle
G3PATP
NADPHStarch(storage)
Sucrose (export)
Chloroplast
Light
H2O
O2
Figure 10.21
Sugarcane
Mesophyllcell
Bundle-sheathcell
C4 CO2
Organic acid
CO2
CalvinCycle
Sugar
(a) Spatial separation of steps (b) Temporal separation of steps
CO2
Organic acid
CO2
CalvinCycle
Sugar
Day
Night
CAM
Pineapple
CO2 incorporated(carbon fixation)
CO2 releasedto the Calvincycle
2
1
Wate
r Savin
g A
dapta
tions
Wate
r Savin
g A
dapta
tions
Slide 42
Greenhouse EffectGreenhouse Effect
Sunlight
Radiant heattrapped by CO2
and other gases
Atmosphere
Some heatenergy escapesinto space
Slide 43
So what?So what?
Slide 44
Slide 45