5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

When yeast respires aerobically, it produces carbon dioxide as a bi-product. Here is how to measure the effect of changing temperature on carbon dioxide production from yeast...

- mix together some suger, yeast aand distilled water. Add this mixture to a test tube

- attatch a bung with a delivery tube. Attatch the other end of the delivery tube to a test tube of water

- Put the tube containing the yeast/water/sugar solution in a water bath at 10°.

- leave to warm up for 5 minutes and then count how many bubbles are produced in one minute

- repeat with 4 other test tubes, one at 15°, one at 20°, one at 25° and one at 30°. You should also do one at room temperature as a control

- plot results in a graph and compare/find patterns/anomalies

should all go well, you should conclude that as temperature increases, the rate of respiration (and therefore amount of bubbles) should increase. However, if you have done a water bath past optimum temperature for the enzymes (as respiration is controlled by enzymes), then there will be very little/no data for this tube.

NOTE: You can use the same apparatus but measure the effect on different concentration of sugar, for example, by keeping the water bath the same temp but adding more/less sugar to each tube. the same can be done with volume of water and/or concentration of sugar solution etc