I investigated the effects of temperature (room temperature, 25°C, 30°C) and glucose conc. (1%, 5%, 10%) on the growth of yeast, and measuring its growth by counting the number of yeast cells in 1mm3 at five time points over a 48 hour time period using a haemocytometer. I was provided with 250ml of a 0.1% yeast culture.
1. Label 10 boiling tubes with a number 1 to 10 plus your initials, add the following to each tube then seal the tops with a plug of cotton wool.
- RT 1% - 20mls 0.1% yeast culture + 0.2g glucose
- RT 5% - 20mls 0.1% yeast culture + 1.0g glucose
- RT 10% - 20mls 0.1% yeast culture + 2.0g glucose
- 25°C 1% - 20mls 0.1% yeast culture + 0.2g glucose
- 25°C 5% - 20mls 0.1% yeast culture + 1.0g glucose
- 25°C 10% - 20mls 0.1% yeast culture + 2.0g glucose
- 30°C 1% - 20mls 0.1% yeast culture + 0.2g glucose
- 30°C 5% - 20mls 0.1% yeast culture + 1.0g glucose
- 30°C 10% - 20mls 0.1% yeast culture + 2.0g glucose
- Control - 20mls of water + 0.2g glucose
2. Do an initial count on all tubes and record these readings as T0.
3. Place all the RT (room temp) labelled tubes (1%, 5%, 10%) in a cupboard and note the temperature,
Place all the 25°C and 30°C labelled tubes in the correct water baths.
4. Count the yeast in each tube at the following hourly time intervals: T0, T24, T27, T30, T48.
You should not have two manipulated variables in the experiment. You should run two separate experiments where you compare the temperature in one and the sugar in the other. It is difficult to tell which is having the greater effect on the yeast production, the temperature or the sugar concentration.
The data should be recorded in a table as previously mentioned and a line graph would suffice for reporting purposes.
You need to precise in your measurement of glucose.
You need to use the same water source for all concentrations and controls
Room temperature needs to be controlled in some way, so that it is consistent throughout the course of your experiment.
For recording your data, use a chart--rows could be labled with temp., columns with time....you may need several charts, one for each concentration of glucose.
Y0ou need to have adequate controls in place and to double check your data. Have someone else verify that the information is correct As long as you have adequate controls and your sources have not been compromised, then you should not have any problems.