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Plant Respiration Releases 50% of fixed CO 2 Provides energy for all sinks, source leaves at night & helps source during day!
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Plant Respiration Similar, but more complex than in animals Making precursors, recycling products, releasing energy are also important
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Plant Respiration 1.Glycolysis in cytosol 2.Pyruvate oxidation in mito 3.Krebs cycle in mito 4.Electron transport & chemiosmosis in mito
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Plant Respiration 1.Glycolysis in cytosol 1 glucose -> 2 pyruvate Yields 2 NADH & 2 ATP per glucose Unique features in plants 1.May start with DHAP from cp instead of glucose
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Unique features in plants 1.May start with DHAP from cp instead of glucose 2.May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate
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Plant Respiration 2.May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate Get more ATP/NADH in mito
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Unique features in plants 2.May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate Get more ATP/NADH in mito Replaces substrates
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Plant Respiration 1.Glycolysis in cytosol 1 glucose -> 2 pyruvate Yields 2 NADH & 2 ATP per glucose Anaerobic plants ferment pyr to regenerate NAD+ Form EtOH
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Plant Respiration 1.Glycolysis in cytosol 1 glucose -> 2 pyruvate Yields 2 NADH & 2 ATP per glucose Anaerobic plants ferment pyr to regenerate NAD+ Form EtOH Less toxic than lactate because diffuses away
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Plant Respiration 3.Krebs cycle Similar, but more complex Key role is making intermediates & recycling products
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Plant Respiration 3.Krebs cycle Similar, but more complex Key role is making intermediates & recycling products Many ways to feed in other substrates to burn
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Plant Respiration 3.Krebs cycle Similar, but more complex Key role is making intermediates & recycling products Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis
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Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going
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Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going
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Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going Malic enzyme is key: lets cell burn malate or citrate from other sources
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Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going Malic enzyme is key: lets cell burn malate or citrate from other sources PEPCarboxylase lets cell replace Krebs intermediates used for synthesis
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Plant Respiration Pentose phosphate shunt in cytosol or cp 6 glucose-6P + 12NADP + + 7 H 2 O -> 5 glucose-6P + 6 CO 2 + 12 NADPH +12 H + : makes NADPH & intermediates
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Plant Respiration Pentose phosphate shunt in cytosol or cp makes NADPH & intermediates Uses many Calvin Cycle enzymes
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Plant Respiration Pentose phosphate shunt in cytosol or cp makes NADPH & intermediates Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors
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Plant Respiration Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors Gets Calvin cycle started at dawn
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ATP generation 2 stages 1) e- transport 2) chemiosmotic ATP synthesis
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Three steps transport H+ across membrane 1) NADH dehydrogenase pumps 4 H + / 2 e - 2) Cyt bc 1 pumps 4 H + / 2 e - 3) Cyt c oxidase pumps 2 H + / 2 e - and adds 2 H + to O to form H 2 O
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e- transport Plants have additional enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+
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Additional e- transport enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone
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Additional e- transport enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors
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Additional e- transport enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors Much lower affinity for NADH than complex I
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Additional e- transport enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors Energy is released as heat NADH dehydrogenase in intermembrane space that transfers e- from NADH to UQ w/o pumping H+
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Additional e- transport enzymes! NADH dehydrogenase in intermembrane space that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone "imports" e- from cytoplasmic NADH Much lower affinity for NADH than complex I Energy is released as heat
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Additional e- transport enzymes! NADPH dehydrogenase in intermembrane space that transfers e- from NADPH to UQ w/o pumping H+ Insensitive to rotenone "imports" e- from cytoplasmic NADPH
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Additional e- transport enzymes! Alternative oxidase on matrix side of IM transfers e- from UQ to O 2 w/o pumping H+ Insensitive to Cyanide, Azide or CO Sensitive to SHAM (salicylhydroxamic acid)
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Additional e- transport enzymes! Alternative oxidase on matrix side of IM transfers e- from UQ to O 2 w/o pumping H+ Insensitive to Cyanide, Azide or CO Sensitive to SHAM (salicylhydroxamic acid,) Also found in fungi, trypanosomes & Plasmodium
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Additional e- transport enzymes! Alternative oxidase on matrix side of IM transfers e- from UQ to O 2 w/o pumping H+ Also found in fungi, trypanosomes & Plasmodium Energy lost as heat: can raise Voodoo lilies 25˚ C
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Additional e- transport enzymes! Alternative oxidase on matrix side of IM transfers e- from UQ to O 2 w/o pumping H + Plants also have an uncoupler protein: lets H + in w/o doing work!
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Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency? Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency?
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Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis Generate heat Burn off excess energy captured by photosynthesis Prevalence says they're doing something important! Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis Generate heat Burn off excess energy captured by photosynthesis Prevalence says they're doing something important!
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Regulating Respiration Regulated by demand for ATP, NADPH and substrates
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Glycolysis is allosterically regulated at 3 irreversible steps Hexokinase is allosterically inhibited by its product: G-6P Allosteric site has lower affinity than active site
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Glycolysis is allosterically regulated at 3 irreversible steps Hexokinase is allosterically inhibited by its product: G-6P Pyr kinase is allosterically inhibited by ATP & citrate
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Regulating Glycolysis Main regulatory step is Phosphofructokinase Rate-limiting step Committed step
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Regulating Glycolysis Main regulatory step is Phosphofructokinase Inhibited by Citrate, PEP & ATP Stimulated by ADP
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Regulating Pyruvate DH Mainly by a kinase Inhibited when Pi added
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Regulating Pyruvate DH Mainly by a kinase Inhibited when Pi added NADH, Acetyl CoA, ATP NH4 + inhibit PDH & activate kinase
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Regulating Pyruvate DH Mainly by a kinase Inhibited when Pi added NADH, Acetyl CoA, ATP NH4 + inhibit PDH & activate kinase Activated when no Pi ADP, pyruvate inhibit kinase
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REGULATING THE KREBS CYCLE Krebs cycle is allosterically regulated at 4 enzymes 1)citrate synthase 2)Isocitrate dehydrogenase 3) -ketoglutarate dehydrogenase 4) Malate dehydrogenase
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REGULATING THE KREBS CYCLE Krebs cycle is allosterically regulated at 4 enzymes 1)citrate synthase 2)Isocitrate dehydrogenase 3) -ketoglutarate dehydrogenase 4) Malate dehydrogenase All are inhibited by NADH & products
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Environmental factors 1)Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature
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Environmental factors 1)Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO 2 Respiration declines if pO 2 <5%
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Environmental factors 1)Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO 2 Respiration declines if pO 2 <5% Problem for flooded roots
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Environmental factors 1)Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO 2 Respiration declines if pO 2 <5% Problem for flooded roots 3)pCO 2 Inhibits respiration at 3%
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Environmental factors 1)Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO 2 Respiration declines if pO 2 <5% Problem for flooded roots 3)pCO 2 Inhibits respiration at 3% No obvious effects at 700 ppm, yet biomass reduced
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Mineral Nutrition Studied by soil-free culture in nutrient solutions:
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Mineral Nutrition Studied by soil-free culture in nutrient solutions: Hoagland’s is best known
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Mineral Nutrition Soil-free culture Sand culture: don’t really control nutrients
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Mineral Nutrition Soil-free culture Sand culture: don’t really control nutrients Hydroponics: immerse roots in nutrient solution
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Mineral Nutrition Soil-free culture Sand culture: don’t really control nutrients Hydroponics: immerse roots in nutrient solution Rapidly deplete nutrients & O 2 & alter pH
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Mineral Nutrition Soil-free culture Sand culture: don’t really control nutrients Hydroponics: immerse roots in nutrient solution Rapidly deplete nutrients & O 2 & alter pH Slanted film maintains [nutrients] & O 2
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Mineral Nutrition Soil-free culture Sand culture Hydroponics: immerse roots in nutrient solution Slanted film maintains [nutrients] & O 2 Aeroponics sprays nutrient solution on roots
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Mineral Nutrition Macronutrients CHOPKNS
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