WAEC Biology 2019 Papers

Concept:Anaerobic respiration in yeast breaks down glucose without oxygen to yield ethanol, carbon dioxide, and energy.Explanation:The diagram illustrates yeast, a common organism that performs anaerobic respiration.In this process, glucose is converted into ethanol and carbon dioxide.The balanced chemical equation is:$$\mathrm{C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2 + Energy}$$Here, $\mathrm{C_6H_{12}O_6}$ is glucose, $\mathrm{C_2H_5OH}$ is ethanol, and $\mathrm{CO_2}$ is carbon dioxide.Thus, besides carbon dioxide, the other main product is ethanol.Oxygen, water, and glucose are not produced in this anaerobic reaction.Answer:A. ethanol