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General Morphology and 

 Chemistry of the Cell 



CELLULAR ORGANIZATION 



Cells range in size all the way from the very large egg cells of birds 

 which may measure several inches in diameter down to the minute bac- 

 teria with dimensions as small as 0.0001 millimeter. In part this range 

 is more apparent than real, since the major variant is often due to 

 variation in amount of nonhving material contained such as stored food 

 products, cellular excretions, etc. Nonetheless, cells from comparable 

 tissues of different organisms show easily measurable and consistent dif- 

 ferences in size. For example, the root tip cells of two different flowering 

 plants may differ by a diameter factor of two or more. The relation be- 

 tween surface area and cell volume and the particular level of metabolic 

 activity have long been recognized as important factors in determining 

 cell size. The mechanisms which operate to control cell size are obviously 

 complex and difficult to analyze by virtue of the constant state of change 

 exhibited by the cell. Because most cells measure less than a millimeter 

 in size, it is convenient to express their dimensions in micron units (//) 

 which is one thousandth of a milHmeter (0.001 mm). To determine the 

 dimensions of most cell structures requires the use of even finer units of 

 measurement such as the millimicron (m/<) which corresponds to one 

 thousandth of a micron (0.001/0- Further subdivision of the millmiicron 

 into units of ten gives the Angstrom unit (A). This unit corresponds to 

 one tenth of a millimicron (0.1 m/<) and is used to measure submicro- 



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