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

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?

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

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

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.

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

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.