Biology Practical - Ivestigating Fermentation

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Biology practical – Investigating fermentation 25/11/08 Research Question Which sugars cause yeast to respire anaerobically and produce the most CO2 out of glucose, fructose and lactose? Variables Independent The sugar solution used as a substrate for the yeast. Dependent The amount of carbon dioxide produced by the yeast in 5 minutes. Controlled Temperature of the water bath used to put the yeast in, yeast concentration (30%), sugar concentration (15%.), the volumes of the yeast and sugar solutions (3cm3 each,), all apparatus that is used. Risk assessment There are no real dangerous elements to this experiment, however it is still imperative to follow the general lab safety procedures and rules, (i.e. no running, bags on the side of the lab, etc.) Apparatus list - 1x bung and delivery tube - 3x boiling tubes - 1x test tube rack - 1x ice cream tub - 1x Janus Green indicator - 1x bottle of Paraffin - 1x water bath with built in thermostat (set at 50oc) - 4x large beakers (100cm3) - 1x digital stopwatch - 3x burettes (100cm3) - 1x 30% concentration yeast solution (50cm3) - 3x 15% concentrations of the sugars: glucose (25cm3,) fructose (25cm3,) and lactose (25cm3.) Hypothesis My hypothesis is that the volume of carbon dioxide released from the yeast will be high when it is respiring with glucose and fructose, but with lactose, as it is a disaccharide and the yeast does not contain the enzyme lactase, which is needed to break lactose down. Method 1. For each repeat, the 3 boiling tubes were set up in a test tube rack, each containing 4cm3 of 30% yeast solution and 4cm3 of the 15% sugars: glucose, fructose and lactose. 2. 5 drops of Janus Green solution was then added to the substrate, in order to indicate when the substrate would begin anaerobic respiration. 3. A layer of paraffin oil was then added to the top of the

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