EFFECTS OF TEMPERATURE: CELLULAR SYSTEMS 



785 



consider onlj' the electron-transport systems with their associated phospho- 

 rylations, but also the many other factors controlling respiratory rate and 

 the level of phosphate acceptors in the cells. It would be very informative 

 to know the P : ratios for both normal and DNP-treated preparations 



T-— 



Fig. 15-8. Effects of temperature on the stimulation of 

 tissue slice respiration by 0.0335 mM mM 2,4-dinitro- 

 phenol. The stimulation ratio is Qo^(DXP)/$o, (control). 

 The curves are plotted from the data of Furhman and 

 Field (1942) and are approximate. 



at the different temperatures, and also the levels of the various nucleotides. 

 A knowledge of the effects of temperature on DNP uncoupling in simpler 

 subcellular systems would also be useful in understanding the mechanisms 

 involved. 



(C) Inhibition of bacterial luminescence. The most quantitative studies 

 of temperature-dependent metabolic inhibitions have been done on the 

 bioluminescence of certain bacteria by Johnson and his co-workers at 

 Princeton during the decade of 1942-1952. The results have been uniformly 

 interpreted on the basis of two major temperature-dependent effects: the 

 usual rise in reaction rates with increasing temperature and the equilibrium 

 between active and inactive enzymes. The maxima in the rate-tempera- 

 ture curves are considered to represent a balance between these two factors 

 — below the optimal temperature the enzymes are mainly in the active 

 forms and the rate varies with the temperature in the classic way, while 

 above the optimal temperature the inactivation or reversible denaturation 

 of the enzymes becomes more important. The relations between inhibition 

 and the temperature are usually ascribed to the effects of the inhibitor on 

 the equilibrium between active and inactive forms. Thus, if the inhibitor 



