ENERGY AND BIOLOGICAL PROCESSES 



37 



ENERGY AND BIOLOGICAL PROCESSES 



Energy exchanges provide the key to understanding biological proc- 

 esses. Such a statement either must be obviously true (since the laws 

 of physics and chemistry must be obeyed) or else some vitalistic factors 

 must operate. Since none of the latter has been found necessary, as yet, 

 to explain biological processes, science continues to work along physico- 

 chemical lines. 



The way in which energy is used in biological processes is of some 

 interest, and will be explained with the analogy of a waterfall, as in 

 Fig. 16. 



If, as in the left sketch, the water falls straight down to the ground, it 

 bounces wildly because it has accumulated an enormous speed as it falls 

 from the top. The energy in the water at the top (its ability to do work) 

 is converted to the energy of motion of the water, and when the water 

 strikes the ground level, there is a glorious display of hydropyrotechnics, 

 after which the previously swift water molecules settle down to their new 

 (energy-wise) impoverished state of being like all other water molecules. 

 The energy of the waterfall has been dissipated into heat, for the water 

 at the bottom is now somewhat warmer than it was before. 



In the right-hand sketch, the water falls only a small distance before 

 striking the vanes of a water wheel, which thereby is caused to turn. If 

 the water wheel is connected to something, it can turn that something 



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(a) 



(b) 



Fig. 16. In (a), the water falls freely to the bottom, bounces high because 

 of the large velocity each molecule acquires while falling, and finally settles 

 down to a quiet flow to the right. In (b), the water falls freely only to the first 

 water wheel. The small velocity acquired is imparted to the vanes of the wheel, 

 thereby turning the wheel and causing useful work to be done by whatever is 

 connected with the wheel. The water then falls freely again for a short distance, 

 picking up more velocity, which is imparted to the next wheel. Finally, the 

 water arrives at the bottom with very little energy to dissipate, so there is 

 little wild bouncing, and the water quickly settles down to its quiet flow to the 

 right. 



