CHAPTER IV 



ANAEROBIC PROCESSES 



In organisms that are adapted to permanent anaero- 

 biosis anaerobic processes have to fulfill two requirements, 

 the production of energy and the synthesis of new proto- 

 plasm. In organisms which are only temporarily anaero- 

 bic the production of energy might be the only require- 

 ment. At all events, the synthetic phase of anaerobic 

 metabolism has, so far, received practically no considera- 

 tion in invertebrates ; the following discussion will there- 

 fore deal almost exclusively with the energy-yielding 

 processes. 



We shall study these processes separately for carbohy- 

 drates, fats and proteins, and shall then turn our atten- 

 tion to the anaerobic gas metabolism and to the question 

 of anaerobic enzymes. Most of the work performed with 

 invertebrates has been concerned with the identification 

 of metabolic end products and the rate at which these 

 are formed; intermediate processes have hardly been 

 touched upon. We shall, therefore, treat this latter 

 phase very briefly in this review^ though we do not, by 

 any means, minimize the importance of the knowledge of 

 intermediate metabolism; it is hoped that research may 

 soon be initiated in that direction. 



1. CARBOHYDRATES 



The anaerobic processes liberating energy from carbo- 

 hydrates are essentially oxidation-reduction reactions 

 or molecular rearrangements. The sugar molecule is 

 broken down into smaller units, for example, into two lac- 

 tic acid molecules, and the energy content of the end prod- 

 ucts is less than that of the mother-substance. It was 

 suggested {e.g., Eahn, 1932) that it is the shifting of oxy- 

 gen from the inner to the outer carbon atoms and the mass- 

 ing of oxygen on one carbon atom that liberates energy. 



