An Introduction to Metabolism

The first section of this book has dealt with the basic structures and with many of the complexities of the materials formed by living cells. In the next major section we will look at the chemical reactions that build and maintain a cell and that permit it to grow and to be responsive to external stimuli. These reactions are organized into metabolic sequences or pathways that form a complex, branched, and interconnected network. It would be pointless to try to memorize all of them. However, at this point it will be worthwhile to consider the significance of a few of the major sequences, which describe central pathways of metabolism. 

We humans must digest most foods before we can utilize them. The same is true for most bacteria, which need amino acids generated by the breakdown of 

The catabolic sequences by which cells obtain energy often appear dominant. For animals, fxmgi, and nonphotosynthetic bacteria these pathways are 

priming reactions often provide chemical changes essential to the mechanisms of subsequenf reactions. 

The strategy employed by most cells in the catabolism of several 6-carbon sugars is to convert them to glucose 6-phosphate and, in the several steps outlined in Fig. 10-2, to cleave this hexose phosphate to two equivalent molecules of gjyceraldehyde 3-phosphate. This triose phosphate can then be metabolized further. Notice the chemical nature of the reactions involved in 

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Dagley, S., and Nicholson, D. E. (1970) An Introduction to Metabolic Pathways. John Wiley Sons, New York. 

When Volume I was published early in 20011 thought that Volume II would be ready by the end of the same year. However, updating the first edition to cover the major aspects of the rapidly expanding scope of Biochemistry was more difficult than I had imagined. This second volume brings many topics up-to-date. The first chapter (Chapter 17), which has been available on the Web, is an introduction to metabolism, more extensive than that in Chapter 10. 

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