Kinetics of Haemoglobin in Red Blood Corpuscle 



This difference in speed might be due to one or more of several 

 possible factors : — 



1 Presence of gradients of dissolved gas in the fluid surrounding 

 the corpuscles, thus leading to a retardation owing to the limiting 

 effect of diffusion. 



2 Delay caused by the time of diffusion through the membrane 

 surrounding the corpuscle. 



3 Delay due to the finite thickness of the corpuscle, the first dis- 

 solved gas to enter combining with haemoglobin on the periphery 

 of the corpuscle, and succeeding dissolving gas having to penetrate 

 a finite distance into the corpuscle before combination occurs. 



4 Differences between the chemical kinetics of the reactions of 

 haemoglobin in dilute solution and its concentrated condition 

 inside the red blood corpuscle. 



Table II 



Comparison of speed of various reactions for adult sheep haemoglobin in 



the red blood corpuscle and in homogeneous solution 



Average time for half reaction 

 in seconds (10-20°C) 



O a + Hb -» O s Hb (at p0 2 = 75 mm) 

 CO + Hb -* COHb (at pCO = 75 mm) 

 2 Hb-»0 2 + Hb(/?H6-8) 

 COHb->CO + Hb 



Hartridge and Roughton's control experiments 4 seemed to show 

 conclusively that, under the conditions of their reaction velocity ex- 

 periments, the fluid between the corpuscles must have remained so 

 well stirred that no appreciable concentration gradients of dissolved 

 gas could have existed therein (see also Roughton 6 see pp 3 and 4). 

 If these be accepted, factor I is ruled out. The fact that the difference 

 between the observed overall rate in the corpuscle and in solution dis- 

 appears when the reaction is slow enough, i.e. in the very slow dis- 

 sociation of carboxyhaemoglobin, suggests that there is no appreciable 

 difference in the chemical kinetics per se, and that the observed dis- 

 crepancy must be conditioned by factors 2 and 3, in both of which 

 the rate of diffusion has a limiting effect. Another rather slow reaction, 

 viz. the rate of displacement of 2 from combination with Hb by CO, 

 was also found 14 to proceed at the same rate in the corpuscle (blood 



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