How does yeast respire?
Copy and complete the following using the word list to help you:
So far we have found out that respiration uses up __________ to release ______ from food.
However, sometimes respiration can occur without oxygen.
Yeast can respire without oxygen. We call this __________ ___________________.
When yeast carries out fermentation it feeds off a sugar called __________ and turns it into __________ ________ and _________. This also releases energy for the yeast cells.
How does changing the amount of sugar affect the rate of fermentation?
1. Draw a diagram of the apparatus.
2. Explain how you can tell which tube fermentation is happening fastest in.
3. Plot a graph using the following data. Draw a curve of best fit.
Amount of sugar (g) Height of yeast in tube (cm)
0 0
0.1 1.0
0.2 2.1
0.3 2.9
0.4 3.4
0.5 3.8
0.6 4.4
0.7 4.2
0.8 4.3
0.9 4.4
1.0 4.4
Now use your graph to answer the following questions. Don’t forget to use full sentences.
Glucose Alcohol + Carbon Dioxide +
energy yeast
Fermentation is used in ______________, _______________ and making ______________.
Word list oxygen bread glucose winemaking alcohol
brewing fermentation energy carbon dioxide
1. What does increasing the amount of sugar do to the rate of fermentation?
2. Why do you think this happens?
3. Which result do you think is inaccurate? Draw a circle round it on your graph.
4. Why does the graph level out at the end? (i.e. when a lot of sugar is added).
Extension work
Describe how you could use this apparatus to investigate the effect of temperature on the rate of fermentation.
Predict what you think will happen and sketch a graph of the likely results.
Explain your ideas in full.
