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Plant respiration - chapter 11
The oxidation of sugars to produce usable energy
(ATP), reductant (NADH), and carbon “skeletons” for
biosynthesis.
C12H22O11 + 12O2 --> 12 CO2 + 11 H2O
60 ADP + 60 Pi --> 60 ATP + 60 H2O
Where does it occur?
In the mitochondria of living cells, both photosynthetic
and non-photosynthetic
What are the major steps?
1) Glycolysis
2) citric acid cycle
3) electron transport/oxidative phosphorylation
Fig. 11.1
The mitochondrion
Fig. 11.5
Glycolysis - conversion of carbohydrates into
pyruvate (organic acid) producing some ATP and NADH.
Can happen in presence or absence of O2
If O2, then pyruvate converted to acetyl CoA and
into the citric acid cycle.
If no O2,then “fermentation” occurs, pyruvate is
reduced to lactic acid and/or ethanol.
In aerobic conditions, pyruvate from glycolysis is
converted to acetyl CoA, which enters the citric acid
cycle where most of the NADH is produced.
Fig. 11.6
As in the chloroplast, a double membrane system allows
formation of an internal pH gradient (p.m.f.) that is
used for ATP production.
Fig. 11.10
Mitochondrial electron transport oxidizes NAD(P)H,
and generates a p.m.f. that is used to produce ATP.
O2 is consumed as it acts as the terminal electron acceptor.
This production of ATP is called “oxidative phosphorylation”
Fig. 11.8
What about those carbon skeletons?
The relationship of respiratory intermediates to other
plant biosynthetic pathways.
Fig. 11.13
Respiration and plant carbon balance
Plant growth:
mass/t = C/t
C = C gain in photosynthesis - C loss in respiration
C = photosynthesis - shoot respiration - root respiration
Respiration for “growth” and “maintenance”.
Growth respiration is for the construction of new tissues,
and is associated with increase in mass.
Maintenance is for solute gradients, ion uptake,
rebuilding of degraded compounds, etc.
Questions about plant respiration
How does ATP formation differ in mitochondria and
chloroplasts? What are their similarities?
How might soil flooding affect ATP production of root cells?
What might be the function of the alternative oxidase?
How does the spadix of a skunk cabbage get so warm?