RESPIRATION

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• Lecture 20
• RESPIRATION
• Glycolysis
• and
• Citric acid cycle

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Overview of respiration

• Consists of four processes
• Glycolysis (in cytosol and plastid yields
  pyruvate, ATP and NADH)
• Pentose phosphate pathway (in cytosol and
  plastid yields NADPH)
• Citric acid cycle (in matrix of mitochondria
  pyruvate is oxidized to CO2, yields NADH, FADH2,
  ATP)
• Electron transport chain/oxidative
  phosphorylation (in inner membrane of
  mitochondria transport of electrons from NADH to
  O2, yields ATP)

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Overview of respiration
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Glycolysis A cytosolic and plastidic process
Energy-conserving phase of glycolysis
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Glycolysis A cytosolic and plastidic process
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Glycolysis A cytosolic and plastidic process
Energy-conserving phase of glycolysis
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Glycolysis A cytosolic and plastidic process
In the absence of O2 (e.g. in plant roots in
flooded soil), fermentation regenerates the NAD
needed for glycolysis. - glycolysis can then be
the main source of energy
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Reactions of the oxidative pentose phosphate
pathway
- Alternate route to glycolytic pathway - runs
in cytosol and plastid, but pathway in
plastids predominates - roles in plant
metabolism ? NADH supply for biosyn- thetic
redox reactions ? NADPH supply for
respiration ? supply of biosynthetic
substrates (precursors for DNA, RNA) ?
Generation of Calvin cycle intermediates
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The Citric Acid Cycle A mitochondrial matrix
process
Review Structure of plant mitochondria
Bean
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Reactions and enzymes of the Citric Acid Cycle
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Electron transport chain

• Catalyzes a flow of electrons from NADH to O2
• Electron transport is coupled with formation of
  proton gradient ? used for ATP synthesis
• Consists of 5 complexes
• Complex I (NADH dehydrogenase)
• Complex II (succinate dehydrogenase)
• Complex III (Cytochrome bc1 complex)
• Complex IV (Cytochrome c oxidase)
• Complex V (ATP synthase)

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Organization of mitochondrial electron transport
chain
Plant mitochondria contain additional enzymes (in
green), which do not pump protons.