The aim of this experiment was to investigate the effect of different amounts of a substrate on the respiration rate of yeast and to compare this to the effect of different amounts of glucose on the rate of yeast respiration. The substrate which I chose to further investigate was fructose. Fructose is a fruit sugar which is one of the three, along with glucose and galactose, dietary monosaccharides that are directly absorbed into the bloodstream during digestion.
2% yeast solution
pH meter & data logger
Sensitive digital scale (g)
Fructose (1.0g, 1.5g, 2.0g, 2.5g)
Glucose (1.0g, 1.5g, 2.0g, 2.5g)
Measuring cylinder (cm3)
Independent: Concentration of glucose (1.0g, 1.5g, 2.0g, 2.5g) , concentration of fructose (1.0g, 1.5g, 2.0g, 2.5g) Dependent: Amount of carbon dioxide produced, i.e. rate of yeast respiration Controlled: 2% yeast solution (20cm3), initial temperature of yeast solution (35-40˙C), amount of time that the reaction is measured (180 seconds)
•20cm3 of yeast solution was measured using a measuring cylinder and then poured into a conical flask.
•1.0g of glucose was weighed on a digital balance.
•Hot wáter was poured into a large beaker, and the conical flask containing the yeast was placed inside with a thermometre inside.
•The conical flask was kept inside
The conical flask was held like this until the 2% yeast solution reached an initial temperature between 35-40˙C (specific temperature was noted down) When this temperature was reached, the thermometer was taken out of the conical flask and the conical flask out of the hot wate