Metabolic charts

The paperback atlas concludes with a series of schematic metabolic charts (pp. 407-419). These plates, which are not accompanied by explanatory text apart from a brief introduction on p.406, show simplified versions of the most important synthetic and degradative pathways. The charts are mainly intended for reference, but they can also be used to review previously learned material. The enzymes catalyzing the various reactions are only indicated by their EC numbers. Their names can be found in the systematically arranged and annotated enzyme list (pp. 420-430). 

Large metabolic charts have been designed to display all the major biochemical pathways. Such charts present a bewildering array of interconnected pathways, making it difficult to appreciate relationships between different pathways. The overall operational aspects of metabolism may be clarified by simpler block diagrams that omit details and focus on functional relationships. Such a functional block diagram for a typical heterotrophic aerobic cell is shown in figure 11.4. The metabolism of such a system is symbolized by two functional blocks ... 

Boehringer Mannheim metabolic chart Biocatalysis/Biodegradation DB (BBD) Glycosidase classification ... 

The laboratory diagnosis of inborn errors of metabolism cannot be completed by analysis of amino acids, organic acids, and acylcarnitines alone. Many defects are situated in other parts of the metabolic chart such as the breakdown of nucleotides and glycoproteins or the biosynthesis of cholesterol (and other steroids) or glycoproteins. Accumulating metabolites or biosynthetic intermediates may be analyzed in plasma or urine by a variety of techniques. The most widely used approaches are described here. 

Finally, it must be mentioned that acetyl-CoA is available for a variety of ester and amide syntheses (reactions which helped in the discovery of active acetate). These reactions are merely indicated in the metabolic chart, although very important substances such as acetylcholine, acetylglucosamine, etc., are formed in this manner. 

The metabolic chart also reveals that various foodstuffs and endogenous substances are broken down constantly to produce common intermediates. This is often referred to as forming a common pool of metabolites. Acetyl-CoA is a very typical example it is derived from many different sources. The metabolic pool, therefore, has numerous inlets as well as outlets one of the outlets flow s to the citrate cycle, another to fat synthesis, another to isoprenoid synthesis, etc. Molecules are mixed uniformly in such a pool once submerged in the f>ool, the origin of a molecule (whether from fat or from carbohydrate) can no longer be stated with certainty. This explains how radioactively labeled fragments can be spread over an entire organism. 

The production and utilization of glycoconjugate precursors is more complex than the metabolic chart indicates. Future studies may want to address various sourees of monosaccharides, the organization of metabolic enzymes within the cells, and the... 

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