5.1 The independent variable is the concentration of sucrose.

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3.5.1 The independent variable is the concentration of sucrose.

3.5.2 Test tube A was included as a control group. It contained no sucrose, allowing researchers to compare the gas production with the other test tubes to confirm that any gas produced was due to the presence of sucrose and yeast activity, not other factors.

3.5.3 Based on the information in the table, it can be concluded that as the concentration of sucrose increases, the rate of gas production by yeast cells also increases. This indicates a higher rate of cellular respiration.

3.5.4 This process, known as alcoholic fermentation, is used to produce alcoholic beverages.

• Yeast cells are added to a sugar-rich solution (e.g., fruit juice, grain mash).
• In the absence of oxygen (anaerobic conditions), the yeast breaks down the sugar (like sucrose) into ethanol (alcohol) and carbon dioxide gas.
• The ethanol produced is the main component of alcoholic beverages.
• The carbon dioxide gas is released, often causing bubbling or carbonation.