Transcript Chapter 11 Respiration and lipid metabolism ¤  (Aerobic) respiration:

Chapter 11 Respiration and lipid metabolism
(Aerobic) respiration:
reduced organic compounds (glucose) are oxidized to release free
energy and generate carbon precursors for biosynthesis
¤ In plant cells, reduced carbon is derived from:
sucrose, hexose phosphates, triose phosphates, fructans, lipids,
organic acids, proteins.
From a chemical standpoint, plant respiration:
C12H22O11 +12 O2  12 CO2 + 11 H2O

photosynthesis
Suppression it in transgenic plant is not essential for plant survival
 Metabolic redundancy
p. 264
NAD+-dependent
matrix of Mito.
NADP+ME in cytosol
GTP in animal
NAD+ malic enzyme:
 make possible the complete net oxidation of TCA cycle intermediates
(A) malate; (B) citrate
 to regulate the level of organic acids in the cells, during fruit ripening
Replenish the intermediates of TCA cycle, anaplerotic
 PEP carboxylase and malate dehydrogenase
Replenish malate via
Export too much
Plant, Cell and Environment (1988) 11: 445
Five additional enzymes (green)
Bypass e- transport chain
(Lowering ATP
production)
Specific inhibitors: rotenone, complex I; antimycin, complexIII ;
Cyanide, azide, CO, complexIV ; salicylhydroxamic acid, AOX
Alternative respiration: (p. 272-273)
alternative oxidase involved;
the alternative oxidase is a quinol-oxygen oxidoreductase catalyzes a reduction
oxygen to water, and it does not pump protons;
complexes III and IV are bypassed, energy conservation in the form of ATP
is much smaller when the AOX is active;
is insensitive to cyanide, azide, or carbon monoxide;
is inhibited by salicylhydroxamic acid;
the AOX pathway appears particularly active in thermogenic flowers and it is
primarily responsible for heat production;
salicylic acid initiates this thermogenesis
is induced by a variety of stresses, many of
which can inhibit mitochondria respiration
Voodoo lily
putrid odor
The possible function of alternative respiration:
1. Heat production in certain membranes of the Araceae (the arum family)
2. In most plants, to adjust the relative rates of ATP production and synthesis
of carbon skeletons for use in biosynthetic reactions;
alternative oxidase is regulated by:
a. reversible oxidation/reduction of an intermolecular sulfhydryl bridge;
b. the reduction level of the ubiquinone pool;
c. pyruvate, the substrate of the TCA cycle
3. To prevent a potential overreduction of the ubiquinone pool, which can led
to generation of destructive reactive oxygen species (ROS).
Plastoquinone in chloroplasts
RNS?
Why plant mitochondria require both alternative
oxidase and uncoupling protein mechanisms?
WebEssay 11.4
Some species, such as the arum lilies, are so intensely thermogenic that their flowers
can increase up to 35°C above the surroundings. For example, in Brazil, the
inflorescence of Philodendron selloum is capable of warming to over 40°C at air
temperatures close to freezing (Figure 1)
Thermal image of the inflorescence of Philodendron selloum during thermogenesis.
The warm spadix is visible, because the spathe (V-shaped structure) has been cut away.
Sterile male florets in the center of the spadix are warmest, but the fertile male florets
also produce heat. Female florets at the base of the spadix do not produce significant
heat.