CHAPTER 6 



THE ESSENTIAL NONMETALLIC ELEMENTS OTHER 



THAN CARBON 



Fungus mycelium and spores are composed mainly of compounds of the 

 nonmetallic elements. As a rule, more than 95 per cent of the fungus 

 consists of hydrogen, oxygen, carbon, nitrogen, sulfur, and phosphorus. 

 The nonmetallic essential elements are both structural and functional. 

 The cell wall, which is composed mainly of chitin or cellulose, appears to 

 be the most stable structure of the fungus. Protoplasm is highly labile, 

 and the constituent compounds of protoplasm are continually undergoing 

 destruction, repair, and synthesis. The various structural and functional 

 compounds of organisms are in a state of continual flux (Hevesy, 1947). 

 The turnover of essential elements in functional compounds is more rapid 

 than in structural compounds. 



The terms utilization, assimilation, and dissimilation are frequently 

 used in physiology. Utilization is a broad term and implies that an 

 organism uses or gains some benefit from a specific substance. Fungi 

 utilize water as a solvent but derive neither energy nor substance from it. 

 Assimilation is the incorporation of substances or their degradation 

 products into cellular materials. Assimilation implies synthesis. Dis- 

 similation is the degradation, or breakdown, of complex compounds into 

 simpler ones. This term is particularly applied to those processes such as 

 alcoholic fermentation where intermediate metabolic products accumu- 

 late in the medium. Frequently dissimilation must precede assimilation 

 and may be considered as the first phase of utilization. 



HYDROGEN 



Hydrogen enters into the composition of nearly all organic compounds 

 of interest to physiology except carbon dioxide. This is true of the 

 organic nutrients used by fungi as well as of the fungus protoplasm and 

 other cellular compounds. Elemental hydrogen is not used by fungi. 

 All the hydrogen utilized by fungi is in chemical combination. Certain 

 bacteria (hydrogen bacteria), however, are able to obtain energy by 

 oxidizing hydrogen. 



The importance of water for all living organisms is so great that it 

 seems impossible to conceive of life without water. The formula H2O is 

 really the formula of steam. In the liquid state these simple molecules 



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