Investigate one of the variables that effect respiration in yeast.
Yeast is one of the various single celled fungi that form masses of
miniature circular or oval cells by budding. When placed in sugar
solution the cells multiply and convert the sugar solution into
alcohol and carbon dioxide. Yeasts are used as fermenting agents in
baking, brewing and the making of wine and spirits. Brewers yeast is a
rich source of vitamin B.
Respiration in yeast is the production of the energy in the
mitochondria of the cells. There are 2 types of respiration, Anaerobic
and aerobic. At first aerobic respiration will be present but only
until the oxygen that is already dissolved in the water. When the
oxygen is used up anaerobic respiration will be present which produces
the alcohol. The word equation for anaerobic respiration in yeast is:
Glucose Alcohol + Carbon Dioxide + Energy
Anaerobic respiration is different in humans than it is in yeast
because we break down glucose into lactic acid whereas yeast breaks it
down into alcohol.
There are several different variables in this experiment such as:
The temperature of the water
Amount of Water
Amount of Yeast
Amount of sugar
The time it is left for
In this experiment I will be changing the temperature of the water.
I predict that the hotter the water is the more carbon dioxide bubbles
... middle of paper ...
reason why my test was accurate was that we used a thermometer to
check the temperature that is an accurate means of measuring heat. It
would have been even more accurate if we used an electronic
Improvements to Plan
The only major improvement that I think would have been useful would
be to increase the temperature by only 5 C each time instead of 15 C.
This would help us to get a more accurate measurement of when the
yeast respires best. If I had more time I would have done this and
would have been able to find the optimum temperature for the yeast.
Another improvement would have been to measure the amount of carbon
dioxide given off instead of counting the bubbles. This would have
been a good improvement as bubble sizes change, they are never the
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