STUDIES ON ISOLATED FLAGELLA 



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3 10 30 



VISCOSITY (centipoises) 



Fig. 2. Measurements of swimming speed of normal cells of P. uvella 

 (O) and beat frequency of isolated flagella (%) in media of increased 

 viscosity. 7 ; = viscosity of medium; / = beat frequency. 



The frequency of beat of isolated flagella, determined at 1 1 °C with 

 a stroboscopic method, is very much less sensitive to viscosity changes 

 than is the swimming speed of normal cells. This is consistent with, 

 but by no means proves, the idea that the inefficiency of isolated 

 flagella may be due to an abnormally high internal viscosity. In fact, 

 the results of this and other experiments can be fit rather well by an 

 equation of the form shown in Fig. 2, which was used to draw the 

 line through the points representing measurements of beat frequency. 

 There was no obvious change in amplitude or wavelength of beating 

 in these experiments, but no quantitative measurements of ampli- 

 tude have yet been attempted. If the amplitude is constant, the equa- 

 tion in Fig. 2 implies that the power available for flagellar activity 

 is constant and is the factor which limits the frequency of beat as 

 the viscosity of the medium is increased. If the equivalent internal 

 viscosity of about 15 centipoises indicated by these results is taken 

 into account, the calculated power consumption of the isolated 

 flagella corresponds to use of about 2 or 3 kcal of energy for each 

 mole of ATP dephosphorylated, which is a respectable efficiency. 



The frequency of beat of isolated flagella also varies with ATP 

 concentration, as shown in Fig. 3. These results closely resemble re- 

 sults obtained by other workers with glycerol-extracted sperm flagella, 

 other than those of some mammals (see Bishop, this symposium). The 



