ON CHEMICAL REACTION RATES, ENZYMES 



199 



slope 



A log v 

 A l/T 



2.303 R 



( T in degrees Kelvin ) 



Figure 8-3. Arrhenius Plot of Log Rate vs l/T; Determination of Activation Energy. 



Referring back to Figure 7-3 which describes a process proceeding from 

 an initial state to a final state, we know now from the preceding discussion 

 that it must be modified with the insertion of an activation "hump" or bar- 

 rier (see Figure 8-4). Thus E* is related to the extra heat content, A// } , the 

 heat content change between initial state and "activated" state. 



activated 

 complex 



c 

 UJ 



State 

 (a) 



| uncatalyzed 



State 

 (b) 



Figure 8-4. Enthalpy (a) and Free Energy (b) of Components as They Pass from Initial to 

 Final State Over the Activation Energy Barrier. Note the position of the activated complex, 

 and the energetically easier path of the catalyzed reaction. 



