ABSTRACT
This chapter outlines the major respiratory pathways and demonstrates that, at least in aerobic cells, the mitochondria are the hub of respiratory metabolism. Growth and reproduction involve the synthesis of proteins, polysaccharides, lipids, and nucleic acids from whatever nutrients the cell encounters. The substrates for respiration in plant cells can be protein, lipid, or carbohydrate. Metabolite analysis of the leaves indicated that the inhibition of mitochondrial adenosine triphosphate (ATP) synthesis resulted in an accumulation of photosynthetic products. The cyanide-insensitive alternative pathway and the rotenone-insensitive bypass, which are not directly coupled to ATP synthesis, will affect regulation by adenylates. Evidence that respiration is under the control of adenylates comes from experiments in which an increase in demand for ATP results in an increased rate of respiration. The interpretation is that substrate limits respiration so that when the carbohydrate concentration increases, respiration rises as a consequence.
