NATURE OF LIFE AND LIVING MATERIAL ii 



of representing the numbers of various atoms in cane sugar is 

 C12H22O11; the structural formula is cumbersome. 



The ability of carbon atoms to combine with other carbon atoms 

 and with other types of atoms in the manner illustrated accounts 

 for the almost infinitely great number of carbon-containing com- 

 pounds. Furthermore, in many of these the carbon atoms are ar- 

 ranged in long chains, forming what are actually known to be long 

 molecules. This is the nature of the protein molecules, which will 

 be discussed farther on. 



Solutions. When a substance is scattered in a liquid so that 

 the molecules are separated, it is stated that the substance has dis- 

 solved. In a true solution the molecules are equally distributed and 

 do not settle out. Most of the compounds which are important in 

 living materials dissolve rather freely in water, but the living sub- 

 stance, protoplasm, does not itself dissolve. Some substances, for 

 instance fats, which are organic compounds, do not dissolve in 

 water and hence are not found uniformly distributed in the living 

 material. 



Ions. When inorganic molecules, for example, caustic soda, 

 NaOH, dissolve in water, some or nearly all of the molecules sepa- 

 rate into two portions or radicals. By the loosing of electrons each 

 acquires an electric charge. The atom or radical written on the 

 left in the formula acquires a positive charge because it loses an 

 electron while the radical on the right, OH in this case, by gaining 

 an electron becomes negatively charged. In a solution of NaOH, 

 then, are to be found positively charged Na atoms and negatively 

 charged OH radicals. Atoms or radicals so charged are termed ions, 

 and compounds which behave in this way are known as electro- 

 lytes. In general, organic compounds, that is, the complex carbon 

 compounds, exhibit much less of this property of ionization than 

 do inorganic compounds. 



Reactions. The formation or breakdown of a molecule is 

 called a reaction. Reactions are written in the form of equations. 



