Transcript Light - plant phys

Photosynthesis
The Source of most Biological Energy
Trapped in Photosynthesis
Energy Converted to Chemical Bonds
Respiration: CH2O + O2
CO2 + H2O + ATP
Krebs cycle CO2
ETS + Ox Phos O2
glycolysis
sugar cytosol pyruvate mitochondrion NADH mitochondrion H2O
matrix
cristae
ATP
ATP
Photosynthesis: CH2O + O2
CO2 + H2O + light
sucrose
Calvin cycle CO2
LR + P Phos O2
sugar synthesis triose chloroplast NADPH chloroplast H2O
cytosol
stroma
thylakoid Light
ATP
Light: An Energy Waveform With Particle Properties Too
wavelength
violet blue green yellow orange red
400
500
600
700 nm
wavelength (nm)
10-9 meter
0.000000001 meter!
Light: An Energy Waveform With Particle Properties Too
wavelength
visible spectrum
400
500
600
700 nm
wavelength (nm)
10-9 meter
0.000000001 meter!
White light: all the colors humans can see at once
QuickTime™ and a
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http://www.alanbauer.com/photogallery/Water/Rainbow%20over%20Case%20Inlet-Horz.jpg
http://www.chez.com/uvinnovatio
n/site/images/introduction/apple_l
ogo.gif
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Which side of our
brains are we using?
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http://jojoretrotoybox.homestead.com/files/Rainbow_Brite_Logo_2.jpg
QuickTime™ and a
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Qui ckTime™ and a
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are needed to see this pictur e.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.astrostreasureches
t.net/websmurfclub/images/pin
smurfoncloudrainbow.jpg
http://www.tvtome.com/images/shows/4/8/40-11946.jpg
http://www.coreywolfe.com/NOV%202004/mlp.jpg
White Light
Green is reflected!
Leaf Pigments
Absorb Most
Colors
Light: An Energy Waveform With Particle Properties Too
amplitude
brightness
intensity
Many metric units for different purposes
We will use an easy-to-remember English unit: foot-candle
0 fc = darkness
100 fc = living room
1,000 fc = CT winter day
10,000 fc = June 21, noon, equator, 0 humidity
Photosynthetic Rate
What wavelengths of light drive
photosynthesis?
100%
0
Action Spectrum
green light
reflected
some still drives
photosynthesis
400
visible spectrum
500
600
wavelength (nm)
700 nm
Light beyond 700 nm
has insufficient
energy to drive
photosynthesis
Photosystem II
chlorophyll b
Light
P450
lutein
P470
to:
ETS
e-
zeaxanthin
P480
ß-carotene
P500
In each energy transfer
some energy is lost as heat:
2nd law of thermodynamics.
from:
H2O
lycopene
P510
echlorophyll b
But enough energy
is passed to P680 to
eject an electron to the
electron transport system.
P650
chlorophyll a
P680
Chlorophyll a
Chlorophyll b
CH2
CH2
HC
H3C
CH3
H
N
N
Mg
H
N
H3C
HC
C2H5 H3C
H
N
H
CH3
C2H5
N
Mg
H
N
H3C
H
N
H
H
CH2 O=COCH O
3
O=C
O
H2C
CH
H3C C
CH2
H2C
CH2
H3C CH
CH2
H2C
CH2
H3C CH
CH2
H2C
CH2
HC
H3C CH3
H2C
CH3
H
H
CH2 O=COCH O
3
O=C
O
H2C
CH
H3C C
CH2
H2C
CH2
H3C CH
CH2
H2C
CH2
H3C CH
CH2
H2C
CH2
HC
H3C CH3
Photosynthetic
pigments are
amphipathic
CH3
CH3
CH3
CH3
CH
HC
C CH3
HC
H3C
H
H2C
Zeaxanthin
HO
CHO
H
N
ß-Carotene
CH
HC
C CH3
HC
H3C
CH
HC
C CH3
HC
CH
HC
C CH3
HC
CH
HC
CH
H3C C
CH
HC
CH
H3C C
CH
HC
CH3
H3C
CH
HC
CH
H3C C
CH
HC
CH
H3C C
CH
HC
CH3
H3C
H3C
H3C
OH
Lutein
100%
What intensities of light drive
photosynthesis?
Reaction Rate
Photosynthesis
add to reserve
grow
reproduce
Respiration
Using
reserves and
may die
0
0 10
100
compensation
point
1,000
10,000 fc
Light Intensity (fc)
The example plant shown here “breaks even” at an
intensity we have in our homes…a house plant!
100%
What intensities of light drive
photosynthesis?
Reaction Rate
Photosynthesis A
0
Photosynthesis B
Respiration
Shade tolerant
plant dies in
intense light!
0 10
100
compensation
points
1,000
10,000 fc
Light Intensity (fc)
The second example plant shown here cannot
survive in our homes…it is a sun-loving crop plant!
The Z-scheme of the Light Reactions: An Energy Diagram
-2.0
reducing
P700*
FeS
-1.5
-1.0
Em (volts)
0.5
1.0
1.5
2.0
cyt b
Pheo
PQ
0
ATP
2 H2O
cyt f
PC
ADP+Pi
4 eO 2 + 4 H+
oxidizing
P680
PS II
eH+
NADP+
NADPH
P680*
-0.5
Fd
FNR
P700
PS I
The Calvin Cycle has Three Phases
P-C-C-C-C-C-P
CO2
ribulose-1,5bisphosphate
rubisco
carboxylation
ADP
C-C-C-P
3-phosphoglycerate
regeneration
ATP
sucrose for transport
starch for storage
reduction
C-C-C-P
glyceraldehyde3-phosphate
ATP
NADPH
NADP+
ADP + Pi
Let’s Do Some Stoichiometry:
3 x 5 = 15 C
3 ADP
3
P-C-C-C-C-C-P
CO2
3 ribulose-1,5bisphosphate
rubisco
carboxylation
6 C-C-C-P
3-phosphoglycerate
6
3 ATP
ATP 6
reduction
NADPH
5
5 x 3 = 15 C
6
6 C-C-C-P
NADP+
To take off 3 carbons:
glyceraldehyde- 6 ADP + Pi
sucrose for transport
6
3-phosphate
1
starch for storage
regeneration
complex
shuffling
More Stoichiometry:
3 ADP
3
P-C-C-C-C-C-P
CO2
3 ribulose-1,5bisphosphate
rubisco
carboxylation
6 C-C-C-P
3 ATP
3-phosphoglycerate
sucrose and
6
starch are not
ATP 6
reduction
3-carbon
NADPH
5
compounds!
6
6 C-C-C-P
NADP+
To take off 3 carbons:
glyceraldehyde- 6 ADP + Pi
sucrose for transport
6
3-phosphate
1
starch for storage
regeneration
complex
shuffling
The Calvin Cycle and Light Reactions are interdependent
H2O
O2
Light Reactions
thylakoid
chlorophyll, etc.
ADP + Pi NADP+
Calvin Cycle
NADPH ATP
rubisco, etc.
stroma
CO2
(CH2O)3
The Calvin Cycle cannot operate in darkness!
“Dark Reactions?”
Photosynthesis: Review and Expansion
CO2 + H2O
light
chlorophyll
O2 + CH2O
Light Reactions: perhaps 25 steps
ADP + P +NADP + H2O
light
chlorophyll
We have been
hiding considerable
truth from you!
Not 1 step…
more like 50!
O2 + NADPH2 + ATP
Interdependent!
Calvin Cycle Reactions: perhaps 25 steps AKA: Dark Reactions
ATP + NADPH2 + CO2
In sum:
CO2 + H2O
CH2O + NADP + ADP + P
light
O2 + CH2O
chlorophyll
The light and Calvin cycle reactions are interdependent…
no dark reactions!
RuBisCO: an ancient enzyme with a modern problem
RuBP + CO2
RuBisCO
RuBisCO often constitutes up to 40% of the
protein in a plant…to ensure enough
photosynthesis is achieved
1% in air O=C=O
RuBP + O2
20% in air O=O
2 x P-C-C-C (a triose relative)
RuBisCO
P-C-C-C (a triose relative)
+ P-C-C
2 x CO2
photorespiration
• Early in evolution of photosynthesis the atmosphere was
anaerobic, so RuBisCo evolved without a problem.
• As photosynthesis was successful, competitive inhibition
from oxygen was essentially a negative feedback.
• Evolution has not yet replaced RuBisCO.
• But several workarounds have evolved…
C4 Photosynthesis: The first fixation is a 4-carbon compound
Mesophyll Cell
Bundle Sheath Cell
regeneration
C3 acid
phosphoenol
pyruvate
HCO3pepc
C4 acid
plasmodesmata
C3 acid
Calvin cycle
rubisco
CO2
decarboxylation
C4 acid
carboxylation
atm
CO2
The C4 and C3 reactions are spatially separated
C4
Zea mays
Leaves
bundle
sheath
mesophyll
PEPc expression in leaf cs
http://botit.botany.wisc.edu/images/130/Leaf/Zea_leaf_cross_section/
Major_vein_MC.jpg
http://www.conabio.gob.mx/malezasdemexico/a
steraceae/flaveria-trinervia/imagenes/rama.jpg
RubisCO expression in leaf cs
Flaveria bidentis
http://www.uni-duesseldorf.de/home/Jahrbuch/2002/Grieshaber/Grafik/Grieshaber05.gif
http://wings.buffalo.edu/academic/department/fnsm/
bio-sci/facultyart.GIFS/Berryart.gif
Zea mays leaf cross section showing classic Kranz anatomy
Zea mays leaf cross section
These bulliform cells lose water and the leaf rolls…which way?
C4 Photosynthesis: A cycle requiring ATP and NADPH
NADP malic enzyme type
Bundle Sheath Cell
Mesophyll Cell
ADP
HCO3pepc
carbonic
anhydrase
atm
CO2
pyruvatephopsphate
dikinase
Pi
CCCOOpyruvate
NADPH
NADP+
CCCCOOoxaloacetate
-OOCCCCOOmalate
malate
dehydrogenase
plasmodesmata
P
CCCOOphosphoenol
pyruvate
ATP
CCCOOpyruvate
NADPH
malic
enzyme
NADP+
Calvin
cycle
rubisco
CO2
-OOCCCCOOmalate
The C4 and C3 reactions are spatially separated
CAM Photosynthesis: Crassulacean Acid Metabolism
At Night
In Daylight
starch
triose
phosphate
phosphoenol
pyruvate
low pH
HCO3-
malic
acid
higher pH
NADPH
pepc
NAD+
malate
NADH
malic
oxaloacetate
dehydrogenase
atm
CO2
starch
Calvin
cycle
pyruvate
rubisco
CO2
malic
acid
malic
enzyme
NADP+
malate
stomata open!
stomata closed!
The C4 and C3 reactions are temporally separated
Sedum leaf cross-section (a CAM
plant)Note the lack of palisade/spongy differentiation
Sedum leaf cross-section (a CAM
plant)Note the lack of Kranz anatomy