Properties and Activities of Living Protoplasm 85 



the proportion of the atoms difTers. The physiologic effects are differ- 

 ent also — carbon dioxide stimulates breathing, while carbon monoxide 

 stops it. Compounds may be divided into organic and inorganic. Or- 

 ganic compounds are commonly referred to as those which contain car- 

 bon (with the exception of the carbonates, containing -CO3), while 

 inorganic compounds are those which have their origin in, or are asso- 

 ciated with, the mineral world, such as rocks, ores, soils, the constitu- 

 ents of the natural atmosphere, etc. There are approximately 300,000 

 carbon-containing compounds known. Examples of organic compounds 

 are marsh gas or methane (CH4), ethyl alcohol (C2H5OH), and a sugar 

 (G12H22O11), while examples of inorganic compounds are water (H2O), 

 table salt (NaCl), sulfuric acid (H2SO4), and lime or calcium carbonate 

 (CaCOs). A mixture is composed of two or more substances which are 

 not combined firmly (each of which retains its own properties) and need 

 not be in any definite proportion. The composition of a mixture may 

 vary, and the constituents usually may be present in different propor- 

 tions in different mixtures. For example, the atmosphere is a mixture of 

 such gases as hydrogen, nitrogen, oxygen, etc., which may vary in their 

 proportions in different atmospheres. 



The following elements (with their symbols) are found in average 

 protoplasm (those essential to life being indicated by *) : 



Oxygen (O) (76.0%)* 



Carbon (C) (10.5%)* I qq^ f ,u ■ u. 



Hydrogen (H) (10.0%)* f 99% of the weight 



Nitrogen (N) (2.5%)* j 



Phosphorus (P) (0.3%)* 

 Potassium (K) (0.3%)* 

 Sulfur (S) (0.2%)* 



Magnesium (Mg) (0.02%)* 1 About 1% of the weight 



Iron (Fe) (0.01%)* f ^^^^"^ ^ ^"^ °^ *^^ "^^^^^^ 



Chlorine (CI) (0.10%) ^ 



Sodium (Na) (0.05%) 



Calcium (Ca) (0.02%) J 



Chlorine and sodium do not seem to be essential for most plants, while 

 calcium is unessential for certain lower animals. In addition to those 

 listed, certain types of protoplasm at times are found to contain other 

 elements in small amounts. 



In general, the elements listed above are not free in the protoplasm 

 but are combined as compounds such as the following: glucides (in- 

 cluding carbohydrates), lipids (including fats), proteins, inorganic salts, 

 water, vitamins, and enzymes. 



