CO₂ production increases with time for all fermentable sugars. Glucose produces the highest volume of CO₂ because it enters glycolysis directly without prior enzymatic breakdown. Fructose shows a similar trend to glucose since it is readily converted into glycolytic intermediates. Sucrose exhibits a slight delay because it must first be hydrolysed into glucose and fructose by the enzyme invertase. Maltose supports moderate respiration after hydrolysis by maltase. Galactose produces comparatively less CO₂ because it requires additional metabolic conversion before entering glycolysis. Lactose shows little or no CO₂ production because Saccharomyces cerevisiae does not naturally produce lactase (β-galactosidase). The graph demonstrates that the chemical structure of a sugar and the enzymes available in yeast determine the rate of cellular respiration.