Plant respiration - chapter 11 The oxidation of sugars to produce usable energy (ATP), reductant (NADH), and carbon “skeletons” for biosynthesis. C 12 H 22 O O 2 --> 12 CO H 2 O 60 ADP + 60 P i --> 60 ATP + 60 H 2 O 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 O 2 If O 2, then pyruvate converted to acetyl CoA and into the citric acid cycle. If no O 2,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

Mitochondrial electron transport oxidizes NAD(P)H, and generates a p.m.f. that is used to produce ATP. O 2 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

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?