Amphibolic pathway

Amphibolic pathway. A metabolic pathway that functions in both catabolism and anabolism. 

Amphibolic Pathways Explain, giving examples, what is meant by the statement that the citric acid cycle is amphibolic. 

Apart from the production of NADH and FADH2, which are the high-energy fuels of electron transport, the citric acid cycle has two other major functions. Several of its intermediate compounds are used to synthesize other cell constituents. This, the provision of molecules for other metabolic or biosynthetic pathways, is the anabolic function of the cycle (Table 12.1). Alternatively, certain other processes occurring within the cell may produce intermediates of the citric acid cycle. These compounds enter the reactions of the cycle, and their degradation involves the catabolic role of the cycle. These two major capabilities classify the citric acid cycle as an amphibolic pathway (Greek amphi meaning both sides ). 

Some pathways can be either anabolic or catabolic, depending on the energy condition.s in the cell. They are referred to as amphibolic pathways. 

Amphibolic pathways can function in both anabolic and catabolic processes. The citric acid cycle is obviously catabolic, because acetyl groups are oxidized to form C02 and energy is conserved in reduced coenzyme molecules. The citric acid cycle is also anabolic, because several citric acid cycle intermediates are precursors in biosynthetic pathways (Figure 9.10). For example,... 

Clearly, the reactions of glycolysis and the citric acid cycle are central to both anabolic and catabolic cellular activities. Metabolic pathways that function in both anabolism and catabolism are called amphibolic pathways. Consider for a moment the difficulties that the dual nature of these pathways could present to the cell. When the cell is actively growing, there is a great demand for biosynthetic precursors to build new cell structures. A close look at Figure 22.13 shows us that periods of active cell growth and biosynthesis may deplete the supply of citric acid cycle intermediates. The problem is, the processes of growth and biosynthesis also require a great deal of ATP ... 

Explain how the citric acid cycle serves as an amphibolic pathway. ] Question 22.15... 

In addition to its role in catabolism, the citric acid cycle also plays an important role in cellular anabolism, or biosynthetic reactions. Many of the citric acid cycle intermediates are precursors for the s)mthesis of amino acids and macromolecules required by the cell. A pathway that functions in both catabolic and anabolic reactions is called an amphibolic pathway. 

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