Elements of biology, with special Elements of biology, with special reference to their rôle in the lives of animals elementsofbiolog00buch Year: 1933 78 ELEMENTS OF BIOLOGY specifically mean the breakdown of sugar by yeasts. The reaction by which the yeast breaks down grape sugar is usually written: 5ugar alcohol carbon dioxide CeHisOe = ^lCsHbOH + 1CO2 . The particular substance which effects this splitting of the sugar molecule is known as an enzyme, this particular enzyme being named zymase. Yeasts may ferment starches and other carbohy- drates, but the reaction in these cases takes place
Elements of biology, with special Elements of biology, with special reference to their rôle in the lives of animals elementsofbiolog00buch Year: 1933 78 ELEMENTS OF BIOLOGY specifically mean the breakdown of sugar by yeasts. The reaction by which the yeast breaks down grape sugar is usually written: 5ugar alcohol carbon dioxide CeHisOe = ^lCsHbOH + 1CO2 . The particular substance which effects this splitting of the sugar molecule is known as an enzyme, this particular enzyme being named zymase. Yeasts may ferment starches and other carbohy- drates, but the reaction in these cases takes place in several steps, a diflferent enzyme effecting each step, finally converting the carbohy- drate into the form of grape sugar and then zymase acts to produce alcohol and carbon dioxide. Hence there may be a chain of enzyme reactions involved in a living process. AGENT SUBSTANCE A ^-s-^ SUBSTANCE B PRODUCT Fig. 25.—Scheme the acti\ation of a chemical reaction by a colloidal catalytic agent. It is assumed that substance A and substance B, because of their electrical characteristics, do not ordinarily react with each other. Both are taken up (adsorbed) by the agent, and their contact with the agent so alters their electrical properties that they react and produce a third substance which is dif- ferent from either. Catalysis. In the non-living world a class of substances are known which also effect reactions without being used up in the process. These are termed catalysts (Fig. 25). The phenomenon of catalysis may be illustrated by the common device known as a platinum sponge. When held over escaping illuminating gas it ap- pears to accumulate the molecules of the oxygen in the air and the gas molecules in such fashion that they unite and a flame results.
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