Question

1. In the first set of experiments, you dissolve 1g yeast in either water, or 10% solutions of different sugars. At room temperature, you set up the eudiometers in parallel, with lots of air in each flask before you begin. These are the results. Plot them using the scatter plot function, set the Y intercept=0, and display the equations of the trendlines on the chart, with the title and axes carefully labeled. You can select/copy/paste the data shown in each table by clicking the little icon in the upper left hand corner or you may use the Excel spreadsheet provided on Canvas. Insert your graph below the data table and answer the following questions. For all of the eudiometer experiments the CO₂ is measured in cubic centimeters or milliliters of displacement (of the colored water).

Time (minutes)	no sugar	glucose	sucrose	maltose	lactose	galactose
0	0	0	0	0	0	0
5	0	3	2.8	3.1	0.1	0.1
10	0	6	5.6	6.2	0.2	0.15
15	0	9	8.8	9.3	0.3	0.2
20	0	12	11.5	12.5	0.3	0.3
25	0	15	13.9	15.7	0.3	0.3
30	0	18	17.2	18.9	0.3	0.3
35	0	21	20	22	0.3	0.3
40	0	24	23.5	25	0.3	0.3
45	0	27	26.5	28.5	0.3	0.3
50	0	30	29.5	31.6	0.3	0.3
55	0	33	32.3	34.8	0.3	0.3
60	0	36	35.2	37.8	0.3	0.3

a) Which of the sugars are being used for cellular respiration by yeast at room temperature?

b) What is the rate of CO₂ production for glucose in this experiment?

c) Explain why yeast might not be able to use the other sugars for cellular respiration.

d) Consider the molecular structures of glucose and maltose. How might these results differ if you used 1M solutions instead of 10% solutions?

Answer 1

a) Which of the sugars are being used for cellular respiration by yeast at room temperature?

Yeast utilizes glucose, sucrose, and maltose at room temperature for cellular respiration.

b) What is the rate of CO2 production for glucose in this experiment?

The rate of CO2 production for glucose fermentation is determined by measuring the volume of CO2 produced per minute.

Rate =( volume of CO2 at 5th min – volume of CO2 at 0th min / 5 – 0)

         = ( 3 – 0 / 5-0)

         = 0.6 cm3/min

c) Explain why yeast might not be able to use the other sugars for cellular respiration.

Yeast lacks the enzymes to break down all types of sugar and this is the reason why it cannot metabolize some sugars. In this experiment, the rate of sugar utilization is maltose > glucose > glucose.

d) Consider the molecular structures of glucose and maltose. How might these results differ if you used 1M solutions instead of 10% solutions?

Glucose and maltose molecules will be fermented by yeast until they reach a saturation point. For glucose molecules, fermentation reaction will occur to the maximum up to 0.8 M, so at 1 M solution, the fermentation will be affected.

For Maltose, fermentation occurs to the maximum up to 0.5 M and after that fermentation will be affected.