The Alternative Oxidase

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The Alternative Oxidase
http//www.plantphys.net/article.php?ch11id148
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http//www.plantphys.net/printer.php?ch11id126
Relationship of oxygen consumption rate and
inflorescence (spadix) temperature in Eastern
skunk cabbage Symplocarpus foetidus measured in
the field in Ontario, Canada. The points were
gathered at 24-minute intervals from a single
plant over a 5-day period. Peak respiration
occurs at a spadix temperature of about 18C,
which occurs at an ambient temperature of about
3C. Above this level, the cluster of points at
the upper right demonstrates the inverse
relationship between respiration and spadix
temperature. When ambient temperature dropped
below about 3C, however, heat production could
not be sustained, and spadix temperature dropped
quickly to just above ambient, resulting in the
cluster of points at the lower left.
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Lecture 20 Photosynthesis  
By the end of this lecture you should be able
to Describe photosynthesis as an ecological as
well as a physiological process. Provide an
overview of the mechanics of photosynthesis and
discuss its importance as a physiological and
ecological process. Concepts and terms light
and dark reactions, redox reaction  Discuss
anatomical features of leaves important for
photosynthesis. Concepts and terms leaf
anatomy, chloroplast structure, grana, stroma  
Describe the energy transformations in the light
reactions. Concepts and terms light
absorption, chlorophyll, photosystems I and II,
action spectrum, NADPH, ATP, cyclic and
non-cyclic e flow. Describe chemiosmosis. Describe
the Calvin cycle. Concepts and terms RUBISO,
3PG Assigned reading Chapter 10 in the text.
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From Larcher.
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C6H12O6 6O2 6H2O lt-gt 12H2O 6 CO2
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Respiration vs. photosynthesis C6H12O6 6H2O
gt 6CO2 6H20 DG -686 kcal/mol an exergonic
reaction. Exergonic versus endergonic reactions.
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For a reaction to occur spontaneously, H must
decrease, S must increase, or both must occur.
Spontaneous reaction have negative free
energy. DG Gfinal Ginitial spontaneous
reactions proceed if the change in free energy is
negative. At equilibrium DG 0.
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Photosynthesis can be broadly separated into
light reactions - light dependent dark
reactions - light independent
Light reactions are involved in the
oxidation of water to oxygen reduction of NADP
to NADPH and ATP occur in thylakoid
membranes Dark reactions use NADPH and ATP to
fix CO2 into CH2O occur in stroma matrix of
chloroplasts
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Photosynthesis and respiration are redox
reactions.
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Photosynthetically active radiation.. 400 to 700
nm.
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RUBISCO
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• On thylakoid membrane
• Light absorption
• Excitation energy transfer
• Primary photochemistry
• Electron transport leading to
• oxygen evolution
• production of reducing power, NADPH
• proton translocation
• 5. Formation of ATP

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• In stroma matrix
• CO2 fixation by RUBISCO (C3 and C4 plants) and
  PEPcase in C4 pants.
• Reduction and phosphorylation of phosphoglyceric
  acids to triose phosphate using NADPH and ATP.
• Regeneration of receptors of CO2 (rubp)
• Formation 6-C sugars and starch
• RUBISCORibulose bis phosphate carboxylase-oxygena
  se
• PEPCase Phosphoenolpyruvate carboxylase

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