162 



A CONCEPTUAL INTRODUCTION TO BIOENERGETICS 



(a) 



heat 

 100 % conversion 



(b) 



Figure 7-1. Energy Interconversion, (a); (b) Degradation of Different Forms of 

 Energy into Heat Energy (the "Heat Death"). 



some pertinent chemical transformations, and physiologists have done some- 

 thing toward relating chemical energy and work. The many relationships 

 which must exist in living systems among mechanical, electrochemical, 

 chemical, and heat energies are as yet poorly known. This chapter attempts 

 to summarize the conclusions which arise from a generalized approach to 

 energy transfer, and to indicate how far they can be carried into a descrip- 

 tion of the living system. 



In this account, use will be made of three different types of symbols, 

 small-case letters, capital letters, and script capital letters, which usually 

 refer to 1 gram, to 1 mole, and to the whole system, respectively. The capi- 

 tals and script capitals have the further property of being "variables of 

 state" — being variables the value of which help to define the state or condi- 

 tion of the system or subject, irrespective of past history. This will become 

 more clearly understood as the subject is developed. 



Some Useful Definitions 



Energy (from the Greek word meaning "active in work") — usually defined 

 as the potency for doing work. Remember the difficulties with definition 

 raised in Chapter 2? 



kinetic Energy (KE) — energy of motion; energy contained within a bound- 

 ary by virute of the motion of the parts contained therein. 



Potential Energy (PE) — literally "energy of position' 1 ; more generally 

 energy stored in any metastable but convertible form. 



Heat Energy (HE or q) — in terms of the kinetic theory, identically equal to 

 the kinetic energy of motion (rotations, vibrations, translations) of the com- 

 ponent molecules. 



