870 



EXTERNAL AND INTERNAL FACTORS 



CHAP. 26 



curve"; but they are merely limits within which the actual kinetic curves 

 are confined. The point we are trying to make — in advance of its analyti- 

 cal proof — is that it would be wrong to imagine that the existence of the 

 "roof" OA and the "ceiling" BC will leave unaffected the curves situated 

 entirely within the "permitted area" OXC, and merely force back into this 

 area the curves (or section of curves) that would otherwise cross the limit- 



Fig. 26.6. "Roof" and "ceiling." OA, maximum rate of a diffusion step 

 (proportional to [CO2]); OA ', maximum rate of carboxylation (proportional 

 to [CO2]); BC, maximum rate of primary photochemical process ( = rate of 

 light absorption) (independent of [CO2]); B'C, B"C", maximum rates of 

 catalytic reactions. 



ing lines. To the contrary, the existence of the "roof" and the "ceiling" — 

 as well as that of the potential, higher "roofs" and "ceilings" {OA' , B'C, 

 B"C" in fig. 26.6) — will push down and toward the right even the kinetic 

 curves that would not have approached the limiting values if the limitations 

 were absent. 



We will have opportunity for analytical proof of these statements in 

 subsequent chapters. For example, in chapter 27 we will derive "carbon 

 dioxide curves" of photosynthesis from simple models of the mechanism of 

 entry of carbon dioxide into the photosynthetic reaction ; and we will find 

 there that the sequence of the two reactions: 



