Unit 1 Home Lab 3: Cellular Respiration

Points: 40p

Name:

Purpose (4p)

Lab Summary (6p)

Lab Answers (14p)

1. List the following experimental materials:

a) Kind of yeast used:

b) Kind of water used:

c) Average temperature of the water bath during the experiment:

d) Average room temperature during the experiment (estimate if necessary):

e) Duration of yeast solutions exposure to bath:

• List your results in Tables 3.1 – 3.4.

Table 3.1.  Independent variables and experimental conditions.

Bottle	Sugar	Yeast	Water	Yeast solution height (in cm)	To be heated in warm water bath?
1	1 teasp	2 teasp	¼ cup		No.  Leave this bottle at room temp.
2	1 teasp	2 teasp	¼ cup		Yes.
3	1 teasp	2 teasp	¼ cup		Yes.    Replicates bottle #2
4	1/3 teasp	2 teasp	¼ cup		Yes.
5	No Sugar	2 teasp	¼ cup		Yes.
6			¼ cup

Table 3.2.  Observations of dependent variables.

Bottle	Balloon size	Yeast growth	Other observations
1
2
3
4
5
6

Table 3.3.  Balloon size and solution height measurements.

Bottle	Circumference, C (cm)	Uncertainty in C, ΔC	Radius (long axis, R; cm)	Uncertainty in R, ΔR	New height of yeast solution (in cm)
1
2
3
4
5
6

• In Table 3.4, record yeast growth and estimated volume of each balloon on Bottles 1-6.

1. Yeast growth  =  New height (in Table 3.3)  –  Original height (in Table 3.1)

• If the balloon did not inflate, it has a volume of zero.

• To estimate the volume of each balloon, use the following formula for the approximate volume of an ellipsoid with a horizontal circumference C and long axis radius R (from Table 3.3):

Volume  ≈  2/19 × (C × C × R)

• To estimate the fractional uncertainty in the volume, use this formula:

      ΔV≈2× (ΔC + ΔR)/C

Table 3.4.  Yeast growth and balloon volume.

Bottle	Independent Variable	Yeast growth:  (Change in solution height)	Balloon Volume (cm3)	Uncertainty in Balloon Volume estimate (ΔV)
1	No heating
2	Control 1
3	Control 2
4	1/3 teaspoon sugar
5	No sugar
6

• Outline the experimental questions in this yeast activity (in a paragraph or two).

• Describe what is measured by the balloon volume.  How does it correlate with yeast growth?

• Compare Bottles # 2 & 3. Are they very different? Discuss the utility of having a duplicate measurement when considering the precision of your experimental technique.

• Compare Bottles # 1 to 2 & 3 and discuss the effect of temperature on cellular respiration in yeast.

• Compare Bottles # 2, 3, 4, 5 and discuss the effect of sugar on cellular respiration in yeast.

• Discuss results obtained with your experimental Bottle #6 in comparison with the other experimental conditions.

1. In a paragraph or two, describe your conclusions, thoughts about what you learned about cellular respiration, and/or things that went wrong.

Discussion and Conclusions (16p)

 

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