Properties and Activities of Living Protoplasm 93 



plasm from nonliving chemicals. Living protoplasm has the unique and 

 characteristic ability to change the potential energy of the large mole- 

 cules of carbohydrates, fats, and proteins into kinetic energy and heat as 

 the larger molecules are changed to simpler forms. Metabolism may be 

 divided into (1) anaholism (a -nab' o lizm) (Gr. ana, up; hole, build), in 

 which the chemical processes unite simpler substances to form more com- 

 plex substances, with the production of new protoplasm, growth, and the 

 storage of energy, and (2) catabolism (ka -tab' o lizm (Gr. kata, down; 

 hole, throw), in which complex substances are broken down, protoplasm 

 may be used up, and energy released. Both anabolism and catabolism oc- 

 cur constantly and simultaneously. In young organisms or in younger 

 parts of older organisms, anabolism predominates over catabolism; during 

 maturity the two are more or less balanced; in old age catabolism pre- 

 dominates over anabolism. Certain protoplasms naturally metabolize at a 

 high rate, while others have a lower rate. The metabolic rate of a partic- 

 ular individual may vary from time to time, being influenced by age, 

 height and weight, sex, activity, certain endocrine secretions, general 

 health, etc. 



The hasal metabolic rate is the measurement of the amount of energy 

 expended (heat given off) just for mere living purposes, with no work be- 

 ing done and no food being digested. The determination of the hasal me- 

 tabolism of a human being is of great value in determining certain fac- 

 tors from a health standpoint. The characteristic ability of living proto- 

 plasm of organisms to duplicate itself or certain of its parts by synthesizing 

 complex molecules out of simpler ones, under the influence of specific 

 enzymes, is referred to as autosynthesis (aw to -sin' the sis) (Gr. autos, 

 self; synthesis, put together). The duplication of chromosomes, genes, 

 and possibly filterable viruses, and reproduction itself illustrate this 

 phenomenon. 



Certain forces in the molecules which compose genes enable them to 

 rearrange the chemical substances in the protoplasm into the same struc- 

 tural (chemico-physical) pattern which the genes possess. This is essen- 

 tial if the constancy and stability in the inheritance of an organism are 

 to be continued through successive generations. However, occasionally 

 there seem to be changes in the normal structural pattern of genes which 

 result in certain effects and charges known as mutations (mu-ta'shun) 

 (L. mutare, to change). These mutations are one source of variations 

 and form one basis for the statement '^the most invariable thing in life 

 is variability." These and other variations are the causes and effects of 



