1 68 PHYSICAL CHEMISTRY 



Various unsaturated compounds have been supposed to aid in 

 oxidations 'by combining with one atom of the oxygen molecule 

 thus leaving the other free to attack another substance that is 

 not so easily oxidized. According to Bach and Chodat (1904) 

 an oxidase is a mixture of two enzymes, oxygenase and peroxi- 

 dase. The oxygenase combines with O, to form a peroxide which 

 is attacked by the peroxidase, with the liberation of active oxygen 

 that in turn attacks the difficultly oxidizable substance present. 

 H 2 2 can be substituted for these peroxides. One criticism of 

 the study of the oxidases is that relatively easily oxidizable sub- 

 stances have been selected with which to test their activity. It 

 would be interesting to have a list of organic substances arranged 

 in order of oxidizability, as well as a record of the oxidizing 

 power of cell constituents of recognized purity if not known 

 constitution. The author observed that oxyhemoglobin (re- 

 crystallized five times) as well as metahemoglobin (recrystallized 

 seven times) would accelerate the oxidation of a-napthol, aloin 

 and p-phenylene diamine and an alkaline solution of a-napthol -f- 

 p-phenylene diamine, whereas hematin would not accelerate the 

 oxidation of these substances without the addition of H 2 2 . 



Since H 2 2 or some other peroxide is necessary for the activa- 

 tion of the peroxidases of the cell, all cells contain catalase which 

 decomposes H 2 2 with enormous rapidity, with the liberation of 

 inactive oxygen. It has been suggested that catalase protects 

 the protoplasm against oxidation. But how is the oxidation 

 regulated so as to occur at the right place at the right time ? The 

 answer to this seems to lie in cell structure, which will now be 

 considered. 



It was stated in the chapters on the bioelectric phenomena and 

 muscular contraction that when a muscle contracts dextrose dis- 

 appears, the permeability of the cells is increased, lactic acid 

 appears between them, if oxygen is admitted the lactic acid dis- 

 appears, and C0 2 and heat are produced. The simplest explana- 

 tion of this chain of phenomena is that in the muscle fiber lactic 

 acid is produced until the reaction is stopped by the accumulation 

 of this end product. This would make the reaction of the proto- 

 plasm slightly acid, but it need not even reach the isoelectric 

 point of the proteins, so that the proteins may continue to be 

 electronegative. That the cell sap of certain plant cells is acid 



