CONCLUSION 



The first stage in this transformation takes place in the absence of 

 oxygen by a process referred to as anaerobic glycolysis. This is 

 represented as follows : 



Glucose 

 Glucose-6-phosphate 



Fructose- 1 -phosphate 



I 

 Fructose- 1 : 6-diphosphate 



Glyceraldehyde phosphate 



Glyceraldehyde diphosphate 



Diphosphoglyceric acid 



a-Phosphoglyceric acid 



Phosphopyruvic acid 



Pyruvic acid 



Lactic acid 



The presence of cozymase and diaphorase I is essential for the dehydro- 

 genation of glyceraldehyde diphosphate to diphosphoglyceric acid and 

 of pyruvic acid to lactic acid. 



This series of changes represents the biochemical reactions that 

 occur during the contraction of muscle, but the recovery of muscle to 

 its original state involves another series of changes, which provides 

 the energy necessary for the reconversion of most of the lactic acid 

 back to glucose and thence into glycogen, in which form carbohydrate 

 is stored in the muscle tissue. This energy is derived from the complete 

 oxidation of the remainder of the lactic acid to carbon dioxide and 

 water. This apparently simple transformation, known as respiration, 

 which occurs in bacteria, yeast and protozoa as well as in animal 

 tissues, is in reality exceedingly complex, and again involves ribo- 

 fiavine- and nicotinic acid-containing^ coenzymes at several stages. 

 The lactic acid is first oxidised back to pyruvic acid, which is then 

 further oxidised by one of two routes. 



The first of these is known as the " oxaloacetic acid cycle " and was 

 discovered by A. Szent-Gyorgyi in 1936. This process comprises the 

 fixation of carbon dioxide to pyruvic acid to give oxaloacetic acid, 

 which then takes up hydrogen to yield a mixture of fumaric and malic 

 acids. These subsequently give up the hydrogen again with regenera- 

 tion of oxaloacetic acid : 



40 625 



