232 SPEEDS OF SOME PROCESSES IN BIOLOGICAL SYSTEMS 



Perhaps the psychological effects of isolation, uncertainty, and frustration 

 will prove to be far more important than the effects of weightlessness on the 

 biophysics of the space traveler. The effects of ionizing radiation in free 

 space, unfiltered by the atmosphere, are discussed in the next chapter. 



PROBLEMS 



8- 1 : The rate of denaturation of a protein or of inactivation of an enzyme by heat is 

 dependent upon the concentration of the enzyme in a rather peculiar way, 

 which can be represented as v cc [E] n , where [E] is enzyme concentration and 

 n is the order of the reaction, interpreted as the number of molecules of enzyme 

 which come together to form a cluster in the inactivation process. 



The temperature dependence is normal in that v cc e~ E *l , where E* is the 

 energy of activation, R is the gas constant (2 cal per degree per mole), and T is 

 the temperature in degrees Kelvin. For one case at low concentration, n was found 

 to be independent of temperature, and E* equal to 150,000 cal/mole. 



(a) Calculate the ratio of velocity at 104°F to that at 98.6°F. 



(b) Calculate the ratio for a 10°C rise in temperature. 



(c) Calculate the ratio for a 10°C rise in temperature for a hydrolysis reac- 

 tion for which E* is 20,000 cal/mole. 



(d) Calculate the ratio for a 10°C rise in temperature for a transport process 

 for which E* is 4000 cal/mole. 



8-2: The basal metabolic rate of the "normal" man is about 0.1 hp. Express this in 

 Cal/hr; in watts; in cal/sec. 



8-3: Using Poiseuille's Equation, calculate the pressure which would have to be ap- 

 plied to a No. 17 hypodermic needle (2 cm long, 0.05 cm radius), if a water solu- 

 tion of viscosity 0.01 poises (dyne/cm. sec 2 ) is to be forced, at a rate of 1 cc/sec, 

 into an artery which is already 100 mm Hg average pressure above atmospheric. 



8-4: Under low rates of flow, blood has a viscosity (~0.02 poise) about twice that 

 of water; but under high rates, such as in the capillaries, it flows more easily 

 (~0. 012 poise). Calculate the flow rate through two parallel tubes 1 mm long, 

 of radii 0.001 and 0.005 cm, if the pressure drop is 100 cm Hg. 



8-5: One milliampere of total body current may be fatal. Estimate the path length 

 and average cross-section from hand to hand; and given the fact that the specific 

 conductivity (i.e., of a volume of soln. 1 cm 2 in area and 1 cm long) of a solu- 

 tion of 100 milliequivalents of KC1 per liter (approx concentration of body 

 fluids) is 0.015 ohm" 1 cm" 1 at 98°F, calculate the applied potential sufficient 

 to force 1 ma of current from hand to hand. 



REFERENCES 



1. Newburg, L. H., "Physiology of Heat Regulation (and the Science of Clothing)," 



W. B. Saunders Co., Philadelphia, Pa., 1.949. 



2. Kuno, Y., "Human Perspiration," Charles C. Thomas Publ., Springfield, 111., 



1956. 



