1. Action of yeast
To investigate the effect of substrate concentration on enzyme activity
To look at variables that we can measure
To plot data
To incorporate our understanding of a second concept: osmosis in our explanations

2. Yeast facts Yeast is a fungus
It contains enzymes that break down glucose
This process is called respiration
Yeast can undertake both aerobic and anaerobic respiration
In yeast aerobic respiration produces which gas?

3. Measuring CO2 Production
The gas carbon dioxide is given off
Thinking about conservation of mass – how might this be measured through the experiment?
Gas carbon dioxide forms a foamy layer at the surface.
How might this be measured?
Measure both

4. Practical Each team will measure CO2 production in two ways;
Each team will use a different concentration of sugar solution
Each team will record and then share their results
Sugar solutions to be investigated will be
0M, 0.1M, 0.2M,0.3M,0.5M

5. Method
Add 200ml of sugar solution to a conical flask; This must be warmed to 35C
Add 10g of dried yeast to the conical flask
Weigh
Place in water bath
Weigh and measure height of foam layer every 5 minutes
Do five readings after starting one.

6. Results Time after start of investigation (minutes) 5 10 15 20 25 0.1
Sugar concentration (Molar)
Time after start of investigation (minutes) 5 10 15 20 25
mass
Height
0.1
0.2
0.3
0.5

7. Analysis of results
Plot graphs for height and mass vs sugar concentration
Which variable must go along the variable (note the one you controlled)
What do these data show
Explain them in terms of both substrate concentration and osmosis.
Use clear sentences expressing one idea at a time.