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failed to help select one among the various possibilities. Other tech- 

 niques such as tracer studies and electron magnetic resonance methods 

 may provide more information. 



The mathematical analysis of the reaction equations for the cyto- 

 chrome chain is very complex, no matter which model one chooses. The 

 concentration of each member of the reaction depends on the kinetics and 

 concentrations of all the other members. An electronic computer of 

 some type is almost essential to even discover the concentrations pre- 

 dicted by a given model. Because these computations have so far failed 

 to make it possible to select a particular model, they will not be pursued 

 further here. 



5. Summary of Enzyme Kinetics 



Enzyme-kinetic studies apply to molecular biology the methods of 

 mathematical analysis common to physics and physical chemistry. 

 These strongly reinforce the view that many enzymes catalyze by enter- 

 ing the reaction forming intermediate complexes. In some cases, as 

 with catalase and peroxidase, the intermediates have distinctive spectra 

 which make it possible to follow the details of their formation and 

 destruction. In other cases, as with the hydrolases, the intermediate 

 complexes have been detected by inference from kinetic data. The 

 actions of enzyme inhibitors have also been analyzed mathematically. 

 Inhibitors give some indication of the order of reaction of various enzymes 

 in a chain and also of the type of action involved. 



Enzymes control the rate of most intracellular processes such as 

 biological oxidations. In biological oxidations, there are, in general, 

 many steps between the original substance being metabolized, for 

 example glucose, and the final waste products such as C0 2 and H 2 0. 

 The oxidative steps include those which incorporate an atom of oxygen 

 into the molecule, those which remove a hydrogen atom, and those which 

 remove an electron. All are called biological oxidations. 



Biological oxidations result in the formation of energy-carrier com- 

 pounds, such as ATP, which can move throughout the cell and supply 

 energy to the various life processes such as syntheses and muscular 

 contraction. Much of the ATP in vertebrate cells and in yeast is formed 

 by the cytochrome chain in the mitochondria. The characteristic 

 spectra of some of the members of the chain have allowed their order of 

 reaction to be determined. However, some of the steps in the synthesis 

 of ATP from ADP and (P) are still unknown. 



From the point of view of biophysics, a major contribution of enzyme 

 kinetics is that it forms a basis for the application of thermodynamics to 

 molecular biology. Chapter 22 is concerned with this aspect of enzyme- 

 catalyzed reactions. 



