Plant Respiration Releases 50% of fixed CO 2 Provides energy for all sinks, source leaves at night & helps source during day!

Plant Respiration Similar, but more complex than in animals Making precursors, recycling products, releasing energy are also important

Plant Respiration 1.Glycolysis in cytosol 2.Pyruvate oxidation in mito 3.Krebs cycle in mito 4.Electron transport & chemiosmosis in mito

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

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

Plant Respiration 2.May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate Get more ATP/NADH in mito

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

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

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

Plant Respiration 3.Krebs cycle Similar, but more complex Key role is making intermediates & recycling products

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

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

Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going

Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going

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

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

Plant Respiration Pentose phosphate shunt in cytosol or cp 6 glucose-6P + 12NADP H 2 O -> 5 glucose-6P + 6 CO NADPH +12 H + : makes NADPH & intermediates

Plant Respiration Pentose phosphate shunt in cytosol or cp makes NADPH & intermediates Uses many Calvin Cycle enzymes

Plant Respiration Pentose phosphate shunt in cytosol or cp makes NADPH & intermediates Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors

Plant Respiration Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors Gets Calvin cycle started at dawn

ATP generation 2 stages 1) e- transport 2) chemiosmotic ATP synthesis

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

e- transport Plants have additional enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+

Additional e- transport enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone

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

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

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+

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

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

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)

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

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

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!

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?

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!

Regulating Respiration Regulated by demand for ATP, NADPH and substrates

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

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

Regulating Glycolysis Main regulatory step is Phosphofructokinase Rate-limiting step Committed step

Regulating Glycolysis Main regulatory step is Phosphofructokinase Inhibited by Citrate, PEP & ATP Stimulated by ADP

Regulating Pyruvate DH Mainly by a kinase Inhibited when Pi added

Regulating Pyruvate DH Mainly by a kinase Inhibited when Pi added NADH, Acetyl CoA, ATP NH4 + inhibit PDH & activate kinase

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

REGULATING THE KREBS CYCLE Krebs cycle is allosterically regulated at 4 enzymes 1)citrate synthase 2)Isocitrate dehydrogenase 3)  -ketoglutarate dehydrogenase 4) Malate dehydrogenase

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

Environmental factors 1)Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature

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%

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

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%

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

Mineral Nutrition Studied by soil-free culture in nutrient solutions:

Mineral Nutrition Studied by soil-free culture in nutrient solutions: Hoagland’s is best known

Mineral Nutrition Soil-free culture Sand culture: don’t really control nutrients

Mineral Nutrition Soil-free culture Sand culture: don’t really control nutrients Hydroponics: immerse roots in nutrient solution

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

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

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

Mineral Nutrition Macronutrients CHOPKNS