The Effect of Temperature on Anaerobic Respiration of Yeast
We wanted to find the effect of temperature on anaerobic respiration
of yeast. We investigated how a mixture of yeast, water, sugar, and
flour were affected.
1g of yeast
0.5g of sugar
10g of flour
6 measuring cylinders - to put the sachets in and the 20cm3 of water
Measuring cylinders to measure the water
Thermometers - to keep the same temperature in the water baths
Water baths - at 20ºC, 30ºC, 40ºC, 50ºC, 60ºC
Hot air oven - at 70ºC
Beakers - to use to put the yeast mixture in the cylinders.
We set up the apparatus as shown, and placed 1g of yeast, 0.5g of
sugar, and 10g of flour each into the beakers. Then we added 20cm3 of
water, measured with a measuring cylinder, and stirred the mixture
until there were no bubbles left in it, and it was a smooth paste.
Then the volume of the dough in each was 25cm3 and we poured it into 6
measuring cylinders. Then we placed the 4 cylinders in 10ºC, 30ºC,
40ºC, 50ºC and 60ºC in water baths at those constant temperatures,
maintained with a thermometer. Then we left a cylinder at room
temperature (20ºC) and the last in a hot air oven at 70ºC. Every five
minutes we took a measurement of the volumes in each measuring
cylinder, and took a record of it. We repeated this two times.
I predict that the cylinders above 20ºC will increase in the volume of
the mixture, and that the yeast in the 70ºC hot air oven will
increase, but will then stop rising. When yeast respires
anaerobically, bubbles of carbon dioxide in the tubes above 20ºC will
I have decided to use 10ºC, 20ºC, 30ºC, 40ºC, 50ºC, 60ºC, and 70ºC to
get a good range of results, because in our pilot investigation, w
only used the temperatures 20C and 40C. However, I wanted to see at
what temperature, if at any, the enzymes became denatured, and at what
temperature they began to work. I will do it 3 times to get reliable
Looking at the results, I can see that as the temperature increased,
the volume of the dough increased. E.g. after 30 minutes in the tube
at 10C, the volume went from 23.3cm3 to 29.0cm3. Whereas in the tube
at 50C, it went from 25.1cm3 to 101cm3.
The yeast increased in volume at 50C after 30 minutes, where the
enzymes reached their peak at 101C, then fell as they were denatured
at 30 minutes at 70C, and went back down to 76.7cm3. As I said in my
prediction, when yeast respires anaerobically, bubbles of carbon
dioxide in the tubes that were heated got trapped. This is because the
anaerobic word equation for the...