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Closed stomates
• Closed stomates lead to…– O2 builds up from light reactions
– CO2 is depleted in Calvin cycle• causes problems in Calvin Cycle
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Inefficiency of Rubisco: CO2 vs O2
• Rubisco in Calvin cycle– carbon fixation enzyme
• normally bonds C to RuBP• building sugars
– when O2 concentration is high• Rubisco bonds O to RuBP
• O2 is alternative substrate
• breakdown sugars
photosynthesis
photorespiration
Rubisco = ribulose bisphosphate carboxylase / oxygenase
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Oxygen Concentration
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6Cunstable
intermediate
1C CO2
Calvin cycle review
5CRuBP
3CPGA
ADP
ATP
3CNADP
NADPH
ADP
ATP
G3Pto make glucose
Rubisco
3CG3PC3 plants
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Calvin cycle with O2
5CRuBP
Rubisco
3C2C
lost as CO2 without
making ATP
photorespiration
O2
A good enzyme,gone BAD!
PGA
phosphoglycolate
Impact of Photorespiration:Oxidation of RuBP
loss of carbons CO2reduces production of photosynthesis
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Reducing photorespiration • Separate carbon fixation from Calvin cycle
– C4 plants • physically separate carbon fixation from actual
Calvin cycle• different enzyme to capture CO2
– PEP carboxylase stores carbon in 4C compounds
• different leaf structure
– CAM plants• separate carbon fixation from actual Calvin cycle by
time of day• fix carbon (capture CO2) during night
– store carbon in organic acids
• perform Calvin cycle during day
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C4 plants • A better way to capture CO2
– 1st step before Calvin cycle, fix carbon with enzymePEP carboxylase
• store as 4C compound
– adaptation to hot, dry climates
• have to close stomates a lot
– sugar cane, corn, other grasses…
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PEP carboxylase O2
light reactions
• PEP carboxylase enzyme– higher affinity for CO2 than O2
(better than Rubisco)
– fixes CO2 in 4C compounds
– regenerates CO2 in inner cells for Rubisco phosphoenolpyruvate (3C) + CO2 oxaloacetate (4C)
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C4 photosynthesis
CO2O2
CO2
O2
• Outer cells– light reaction & carbon
fixation– pumps CO2 to inner
cells – keeps O2 away from
inner cells• away from Rubisco
• Inner cells– Calvin cycle– glucose to veins
Physically separated C fixation from Calvin cycle
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CAM (Crassulacean Acid Metabolism)
• Different adaptation to hot, dry climates– separate carbon fixation from Calvin cycle by time
– at night, open stomates & fix carbon in “storage” compounds• organic acids: malic acid, isocitric acid
– in day, close stomates & release CO2 from “storage” compounds to Calvin cycle• increases concentration of CO2 in cells
– succulents, some cacti, pineapple
It’s all inthe timing!
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CAM plants
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C4 vs CAM Summary
C4 plants separate 2 steps of C fixation anatomically in 2 different cells
CAM plants separate 2 steps of C fixation temporally at2 different times
solves CO2 / O2 gas exchange vs. H2O loss challenge
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CR & Photo Review
Mrs. Confrey
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Lab 4
• Conclusions– Pigments
• pigments move at different rates based on solubility in solvent
– Photosynthesis• light & unboiled
chloroplasts produced highest rate of photosynthesis
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Lab 5: Cellular Respiration
• using respirometer to measure rate of O2 consumed
• Conclusions temp = respiration
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Cellular Respiration
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Cellular Respiration
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Glycolysis summary endergonicinvest some ATP
exergonicharvest a little ATP & a little NADH
yield2 ATP2 NADH
like $$in the bank
4ATP
ENERGY INVESTMENT
ENERGY PAYOFF
G3PC-C-C-P
NET YIELD
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10 reactions– convert
glucose (6C) to 2 pyruvate (3C)
– produces: 4 ATP & 2 NADH
– net: 2 ATP & 2 NADH
glucoseC-C-C-C-C-C
fructose-1,6bPP-C-C-C-C-C-C-P
DHAPP-C-C-C
G3PC-C-C-P
pyruvateC-C-C
Glycolysis Overview
DHAP = dihydroxyacetone phosphateG3P = glyceraldehyde-3-phosphate
ATP2
ADP2
ATP4
ADP4
NAD+22
2Pi
enzyme
enzyme
enzyme enzyme
enzyme
enzyme
enzyme
enzyme
2Pi
2H
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Alcohol Fermentation
1C3C 2Cpyruvate ethanol + CO2
NADH NAD+
Regenerates NAD can’t reverse the
reaction
•Bacteria• yeast
•Alcohol production
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Reversible process With O2, lactate is
converted back to pyruvate by the liver
Lactic Acid Fermentation
pyruvate lactic acid3C 3C
NADH NAD+
O2
•Animals•anaerobic exercise (no O2)•Muscle cells•Acid lowers pH of cells (cramping)
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Kreb’s (citric acid) cycle
Acetyl CoA
CO2
2 ATP!• electron carriers
– 6 NADH
– 2 FADH2
– go to ETC!
2 NADH, 2 CO2 2 Pyruvate
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oxidative phosphorylation
O2
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Photosynthesis
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ETC of Photosynthesis
6
5
$$ in the bank…reducing power
to theCalvin Cycle
electron carrier
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PGA6
3
6
1
5
3
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Photophosphorylation
noncyclicphotophosphorylation
cyclicphotophosphorylation
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STUDY!!