CHAPTER I 



ENTRY INTO THE BIOSPHERE 



I. CARBON AND ENERGY 

 In addition to the priming and biosynthetic reactions described in Part 

 Three we mast consider the entry of energy and matter which occurs in 

 certain regions of the biosphere. As we have pointed out, the priming 

 reactions constitute a chemical machine which forms, at the expense of the 

 chemical energy of nutrient molecules, energy-rich bonds of ATP, packets 

 of energy which can be utilized for biosynthesis. Also, during the function- 

 ing of this chemical m.achine construction materials are produced which 

 can be employed for biosynthetic purposes. 



However organisms exist which are capable, by chemical mechanisms of 

 their own, of introducing into their metabolism a supply of external 

 energy, either chemical or electromagnetic in nature. Traditionally, the 

 name chimiosynthesis is given to the synthesis of carbohydrates from 

 CO2 and chemical energy. In this sense, all organisms are chimiosynthetic. 

 But, certain micro-organisms, during the synthesis of carbohydrates, 

 introduce energy derived from the oxidation by oxygen (auto-oxidation) of 

 a constituent of the external medium. Other organisms are capable of 

 carr}dng out photosynthesis, i.e. synthesis of carbohydrates using electro- 

 magnetic energy derived from light. So, by the terms chimiosynthesis and 

 photosynthesis we understand that sugars are synthesized. The term 

 photometabolism refers to other types of metabolic action accomplished 

 by light. 



There are some micro-organisms who obtain all their energy and material 

 from outside the biosphere. These are the autotrophes. They build up 

 all their constituent organic material from COg, HgO and other inorganic 

 substances like ammonia, sulphates and phosphates. For energy they use 

 that derived from the oxidation of substances in the surrounding medium. 

 Photosynthesis, another form of autotrophism, occurs in certain bacteria, 

 in algae, in diatoms, in green plants, etc. 



A. Autotrophic Bacteria 



These organisms do not obtain their nutrient from some other region 

 of the biosphere: the flow of energy and matter through them is derived 

 from the inorganic world. Examples are: the nitrous and nitric bacteria 

 and the colourless sulphur bacteria. 



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