Bio%20226:%20Cell%20and%20Molecular%20Biology

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Plant Respiration Releases 50 of fixed
CO2 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
• Glycolysis in cytosol
• Pyruvate oxidation in mito
• Krebs cycle in mito
• Electron transport
• chemiosmosis in mito

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• Plant Respiration
• Glycolysis in cytosol
• 1 glucose -gt 2 pyruvate
• Yields 2 NADH 2 ATP
• per glucose
• Unique features in plants
• May start with DHAP
• from cp instead of glucose

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• Unique features in plants
• May start with DHAP from cp instead of glucose
• May yield malate cf pyr
• PEP -gtOAA by PEPC, then reduced to malate

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• Plant Respiration
• May yield malate cf pyr
• PEP -gtOAA by PEPC, then reduced to malate
• Get more ATP/NADH in mito

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• Unique features in plants
• May yield malate cf pyr
• PEP -gtOAA by PEPC, then reduced to malate
• Get more ATP/NADH in mito
• Replaces substrates

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• Plant Respiration
• Glycolysis in cytosol
• 1 glucose -gt 2 pyruvate
• Yields 2 NADH 2 ATP
• per glucose
• Anaerobic plants ferment
• pyr to regenerate NAD
• Form EtOH

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• Plant Respiration
• Glycolysis in cytosol
• 1 glucose -gt 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
• Krebs cycle
• Similar, but
• more complex
• Key role is making
• intermediates
• recycling products

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• Plant Respiration
• 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
• 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 H2O -gt 5 glucose-6P 6
  CO2 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 bc1 pumps
4 H/ 2 e- 3) Cyt c oxidase pumps 2 H/ 2 e- and
adds 2 H to O to form H2O
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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 O2 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 O2 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 O2 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 O2 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
• citrate synthase
• Isocitrate dehydrogenase
• 3) a-ketoglutarate dehydrogenase
• 4) Malate dehydrogenase

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• REGULATING THE KREBS CYCLE
• Krebs cycle is allosterically regulated at 4
  enzymes
• citrate synthase
• Isocitrate dehydrogenase
• 3) a-ketoglutarate dehydrogenase
• 4) Malate dehydrogenase
• All are inhibited by NADH
• products

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• Environmental factors
• Temperature
• Rate doubles for each 10 C increase up to
  40
• At higher T start to denature

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• Environmental factors
• Temperature
• Rate doubles for each 10 C increase up to
  40
• At higher T start to denature
• 2) pO2
• Respiration declines if pO2 lt5

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• Environmental factors
• Temperature
• Rate doubles for each 10 C increase up to
  40
• At higher T start to denature
• 2) pO2
• Respiration declines if pO2 lt5
• Problem for flooded roots

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• Environmental factors
• Temperature
• Rate doubles for each 10 C increase up to
  40
• At higher T start to denature
• 2) pO2
• Respiration declines if pO2 lt5
• Problem for flooded roots
• pCO2
• Inhibits respiration at 3

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• Environmental factors
• Temperature
• Rate doubles for each 10 C increase up to
  40
• At higher T start to denature
• 2) pO2
• Respiration declines if pO2 lt5
• Problem for flooded roots
• pCO2
• Inhibits respiration at 3
• No obvious effects at 700 ppm, yet biomass reduced