THE ROLE OF ATP IN METABOLISM

The coenzyme adenosine triphosphate (ATP) acts as the central link between energy-yielding metabolic pathways and energy expenditure on physical and chemical work. The oxidation of metabolic fuels is linked to the phosphorylation of adenosine diphosphate (ADP) to adenosine triphosphate (ATP), while the expenditure of metabolic energy for the synthesis of body constituents, transport of compounds across cell membranes and the contraction of muscle results overall in the hydrolysis of ATP to yield ADP and phosphate ions. The total body content of ATP + ADP is under 350 mmol (about 10 g), but the amount of ATP synthesized and used each day is about 100 mol — about 70 kg, an amount equal to body weight. 

After reading this chapter you should be able to  

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Bergethon, P. R., The Physical Basis of Biochemistry The Foundations of Molecular Biophysics, Springer, New York, 1998. Hanson, R. W., The Role of ATP in Metabolism, Biochem. Educ. 17 86-92, 1989. 

The ways in which energy in the form of ATP is produced and utilized constitute bioenergetics, and will be discussed in greater detail at the end of this chapter. However, before turning to a selection of metabolic pathways, we outline some fundamental notions concerning redox reactions followed by a brief description of the central role of ATP in metabolism as an acceptor and donor of phosphoryl groups, and finally a summary of the types of reactions that we will encounter as we wend our way along a sample of some of the pathways of intermediary metabolism. 

We are now in a position to expand on our earlier statements about the natures of anahohsm and catabohsm. Figure 15.12 is an outline of metabolic pathways that explicitly points out two important features of metabolism the role of electron transfer and the role of ATP in the release and utilization of... 

The importance of phosphates in intermediary metabolism became evident with the discovery of the role of ATP, adenosine diphosphate (ADP), and inorganic phosphate (Pj) in glycolysis (Chapter 17). 

The first metabolic pathway elucidated was the glycolytic pathway during the first half of the 20 century by Embden and Meyerhof. Otto Warburg, Cori and Parnas also made very important contributions relating to glycolytic pathway. Krebs established the citric acid and urea cycles during 1930-40. In 1940, Lipmarm described the central role of ATP in biological systems. 

In 1961 Bob Williams was the first to point out that the role of hydrogen in biology, in bound and protonic forms, made it the ideal element for coupling both metabolic and proton energies to the formation of ATP. The connection made depended upon his realization of the importance of electron-transfer chains in biology and therefore a fundamental role for iron. A long exchange of views with Dr. P. Mitchell has followed. 

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