Burping Yeast: an Investigation of Cellular Respiration

Burping Yeast: An Investigation of Cellular Respiration

Teacher Materials

Learning Goals, Objectives, and Skills 2

Standards Alignments 3

Laboratory Set-Up Manual 5

Instructor Laboratory Guide 7

Answers to Student Questions 8

Post-Lab Extension Activities 11

*Please consider adapting this lab to include some student-centered investigation.

Some suggestions, ideas, and tips can be found in a separate document called "Student-Centered Investigation"

Burping Yeast: An Investigation of Cellular Respiration

Learning Goals, Objectives, and Skills

Student Learning Goals:

·  Students will understand the basic process of cellular respiration.

·  Students will understand the role of enzymes in chemical reactions.

·  Students will understand some of the factors that can influence the rate of enzyme-controlled reactions.

·  Students will understand that starch can be used as an energy source for fermentation.

·  Students will understand that gluten is a type of protein.

Student Learning Objectives:

·  Students will articulate the function of cellular respiration and identify the reactants and products of this reaction.

·  Students will explain the role of enzymes as catalysts that lower the activation energy of biochemical reactions.

·  Students will measure the effect of temperature and other factors on cellular respiration.

·  Students will determine the effect of temperature and other factors on enzyme activity.

·  Students will apply their knowledge of macromolecules to help explain why bread dough rises.

Scientific Inquiry Skills:

·  Students will pose questions and form hypotheses.

·  Students will design and conduct scientific investigations.

·  Students will make measurements and record data.

·  Students will use mathematical operations to analyze and interpret data.

·  Students will generate tables and graphs to present their data.

·  Students will use experimental data to make conclusions about the initial question and to support or refute the stated hypothesis.

·  Students will follow laboratory safety rules and regulations.

Laboratory Technical Skills:

·  Students will demonstrate proper use of micropipettors.

Burping Yeast: An Investigation of Cellular Respiration

Standards Alignments

MA Science and Technology/Engineering Curriculum Framework (2006)

Biology

·  1.2 Describe the basic molecular structures and primary functions of the four major categories of organic molecules (carbohydrates, lipids, proteins, nucleic acids).

·  1.3 Explain the role of enzymes as catalysts that lower the activation energy of biochemical reactions. Identify factors, such as pH and temperature that have an effect on enzymes.

·  2.4 Identify the reactants, products, and basic purposes of photosynthesis and cellular respiration. Explain the interrelated nature of photosynthesis and cellular respiration in the cells of photosynthetic organisms.

·  2.5 Explain the important role that ATP serves in metabolism.

Chemistry

·  7.2 Calculate concentration in terms of molarity. Use molarity to perform solution dilution and solution stoichiometry.

·  7.5 Identify the factors that affect the rate of a chemical reaction (temperature, mixing, concentration, particle size, surface area, catalyst).

Scientific Inquiry Skills

·  SIS1. Make observations, raise questions, and formulate hypotheses.

·  SIS2. Design and conduct scientific investigations.

·  SIS3. Analyze and interpret results of scientific investigations.

·  SIS4. Communicate and apply the results of scientific investigations.

Mathematical Skills

·  Construct and use tables and graphs to interpret data sets.

·  Perform basic statistical procedures to analyze the center and spread of data.

·  Measure with accuracy and precision (e.g., length, volume, mass, temperature, time)

·  Use common prefixes such as milli-, centi-, and kilo-.

DRAFT REVISED MA Science and Technology/Engineering Standards (2013)

*Please note that these are DRAFT standards that have not yet been submitted for formal review or adoption.

Biology

·  HS-LS1-7. Use a model to illustrate that aerobic cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and new bonds form resulting in new compounds and a net transfer of energy. Contrast this process to anaerobic cellular respiration and compare the amount of energy released in each process.

[Clarification Statement: Emphasis is on the conceptual understanding of the inputs and outputs of the process of cellular respiration, lactic acid fermentation and alcoholic fermentation. Students should understand that molecules other than glucose can be broken down to release energy in the form of ATP. Examples of models could include diagrams, chemical equations, and conceptual models.]

[Assessment Boundary: Assessment should not include identification of the steps or specific processes involved in either aerobic or anaerobic cellular respiration.]

·  HS-LS2-3. Construct and revise an explanation based on evidence that the processes of photosynthesis, chemosynthesis, and aerobic and anaerobic respiration are responsible for the cycling of matter and flow of energy through ecosystems. Explain that environmental conditions restrict which reactions can occur.

[Clarification Statement: Examples of environmental conditions can include the availability of sunlight or oxygen.]

[Assessment Boundary: Assessment does not include the specific chemical processes of photosynthesis, chemosynthesis, of either aerobic respiration or anaerobic respiration.]

Chemistry

·  HS-PS1-5. Construct an explanation based on collision theory for why varying conditions influence the rate of a chemical reaction or a dissolving process. Design and test ways to alter various conditions to influence (slow down or accelerate) rates of processes (chemical reactions or dissolving) as they occur.

[Clarification Statement: Explanations should be based on three variables in collision theory: quantity of collisions per unit time, molecular orientation on collision, and energy input needed to induce atomic rearrangements. Conditions that affect these three variables include temperature, pressure, concentrations of reactants, mixing, particle size, surface area, and addition of a catalyst.]

[Assessment Boundary: Assessment is limited to simple reactions in which there are only two reactants and to specifying the change in only one variable at a time.]

NRC Practices

·  Asking questions and defining problems

·  Planning and carrying out investigations

·  Analyzing data

·  Mathematical and computational thinking

·  Constructing explanations and designing solutions

·  Engaging in argument from evidence

·  Obtaining, evaluating, and communicating information

Burping Yeast: An Investigation of Cellular Respiration

Laboratory Set-up Manual

Note: The set-up procedure below is designed for groups of three.

Supply List:

For lab preparation:

·  250-mL Erlenmeyer flask

·  10 g lyophilized yeast

·  9 g glucose

·  round bottom tubes (e.g., Fisher Scientific catalog # 2-565-971) or small containers like portion cups (e.g., Fisher Scientific catalog # NC9698785)

·  2 ´ 5-L containers or carboys with spigots

·  3 ´ 8-L to 10-L water baths OR supplies such as hot plates and ice cubes to maintain three water sources, with temperatures between 15°C–50°C and at least 10°C apart.

For each group:

·  3 ´ 600-mL beakers

·  3 ´ test tubes (25 mm ´ 200 mm) *Taller test tubes are critical because the entire transfer pipette must be completely submerged (e.g., Fisher Scientific catalog # 14-915H)

·  1 ´ test tube rack

·  3 ´ 1-mL graduated transfer pipettes (e.g., Fisher Scientific catalog # 50-819-427)

·  3 ´ metal hex nuts (3/8” stainless steel) *Hex nuts must be large enough to slide over the shaft of the transfer pipette, but small enough to fit into the test tube

·  3 ´ 2.0-mL microcentrifuge tubes

·  1 ´ p1000 micropipettor and pipette tips

·  1 ´ thermometer

·  timer

·  calculator

·  permanent marker (such as Sharpie)

·  tube of glucose solution

·  tube of yeast solution

·  microcentrifuge tube rack or beaker to hold 3 microcentrifuge tubes

Tips for supplies:

·  If you do not have an adequate number of 600-mL beakers, other appropriate containers for mini water baths can be substituted.

·  Graduated 1-mL transfer pipettes can be substituted for the p1000 micropippetors and tips.

·  Consider providing students with reference points for the water temperatures they are using. For example, 22°C is room temperature and 37°C is body temperature. Ask them why they aren’t using boiling water or freezing water (A: the yeast cannot survive at those temperatures).

Lab Set-Up Calendar:

2 weeks before lab:

¨ Check supplies and order any needed materials.

¨ If making any substitutions to the supply list, edit the student protocol accordingly.

1–3 days before lab:

¨ Prepare 50 mL of a 1M glucose solution:

1.  Dissolve 9 g of glucose in 40 mL of water; bring to 50 mL final volume.

2.  Aliquot 12 ´ 2.0-mL glucose solution into round bottom tubes.

3.  Store glucose solution at 4°C until ready to use.

1 day before lab:

¨ Set up student lab stations with all durable materials.

¨ Practice preparing and using a respirometer so demonstration will go smoothly

¨ Determine how you will maintain the temperatures of the three water sources and make any necessary preparations.

Morning of lab:

¨ Set out 1M glucose solution aliquots (1 tube per station)

¨ Prepare 50 mL of a 20% yeast solution. *Must be made fresh the day of the lab*

1.  Dissolve 10 g of yeast into 50 mL of water in Erlenmeyer flask. Add 5 mL of the 1M glucose solution

2.  Store yeast solution uncovered at room temperature until ready to use

¨ Check temperature of water sources and adjust temperatures if necessary. For the best results, use water temperatures between 20°C and 50°C and choose three temperatures that each differ by about 10°C

As students start the pre-lab activity:

¨ “Activate” yeast solution by incubation at about 37°C for ~15 minutes. This can be done by floating an Erlenmeyer flask in a beaker of warm water.

¨ Aliquot 12 ´ 2.0-mL activated 20% yeast solution into round bottom tubes and distribute 1 tube per station

Burping Yeast: An Investigation of Cellular Respiration

Instructor Laboratory Guide

Laboratory Procedure Tips:

1.  Before starting the experiment, ask students to check their materials list to make sure they have everything.

2.  Demonstrate how to set up the respirometer (inverted pipette apparatus) in the test tube so that students have a model from which to work.

3.  Students will work in groups of three; make sure each student in the group gets a chance to set up a respirometer and beaker water bath.

4.  Have the students set up all three respirometers and then the beaker water baths.

5.  When loading the yeast-glucose solution into the transfer pipette bulb, Important! You must get all of the solution down into pipette bulb. Students should completely depress the bulb and then FLIP the pipette BEFORE they release the bulb!

6.  Remind students to fill the test tubes with water from the water bath beakers and insert the test tube into the corresponding beaker so it will be the appropriate temperature.

7.  Since the heated water cools quickly, prepare water for each condition with the expectation that by the time students set up and perform the assay the water will have cooled off. The following represents preparation for one possible set of low-medium-high temperatures:

a.  Student beaker water bath “A” (coolest temperature):
incubate water at room temperature for an experimental target temp of ~22°C

b.  Student beaker water bath “B” (medium temperature):
heat water to 42°C for an experimental target temp of ~37°C

c.  Student beaker water bath “C” (warmest temperature):
heat water to 55°C for an experimental target temp of ~47°C

8.  Students should expect to see ~ 1 bubble/min at 22°C and 5–7 bubbles/min at 37°C and 47°C.

Lab Data Analysis Tip:

While students are working on their lab generate a table on the board or projector to collect class data. Record the total number of bubbles each group obtained for each experimental condition and calculate the class average. You could also have students perform a t-test and calculate a p-value.

Total Number of Bubbles Over 10 Minutes
Condition / Group Number
1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / Class Average
Water Bath “A”
coolest temp.
Water Bath “B”
medium temp.
Water Bath “C”
warmest temp.

Burping Yeast: An Investigation of Cellular Respiration

Answers to Student Questions

Protocol-Embedded:

p. 2:

·  Carbon atoms from pyruvate join with oxygen to become CO2.

·  Yeast release CO2 gas during both respiration and fermentation. The gas forms bubbles in the dough that cause it to rise.

Figure 3: The metal nut keeps the transfer pipette immersed in the water within the test tube.

Pre-Lab:

1.  Cellular respiration is the process by which living things transform the energy stored in macromolecules (“food”) into energy that the cell(s) of the organism can use directly (ATP).

2.  Glucose cannot be used by cells directly, but ATP can be.

3.  Muscle cells are more likely to ferment during exercise because when the muscles are working hard, there is likely to be an inadequate supply of available oxygen to meet the energy demands of the cell by aerobic cellular respiration alone.

4.  Enzymes lower the activation energy required for the cellular respiration reactions to take place.

5.  By counting released bubbles

6.  Sample answer: The higher the temperature, the more bubbles will be released.

7.  Dependent: number of bubbles released; Independent: water temperature

Post-Lab and Analysis:

1.  Because the bubble contain CO2 gas, which is released by the yeast when the ferment. More bubbles indicate a more rapid rate of CO2 production, which in turn indicates a faster rate of fermentation.

2.  Sample graph and data table:

Time

/

Number of Bubbles/Minute

Beaker A
coolest-temperature
Starting Temp: 22°C / Beaker B
medium-temperature
Starting Temp: 33°C / Beaker C
warmest-temperature
Starting Temp: 45°C
Minute 1 / 2 / 2
Minute 2 / 2 / 3
Minute 3 / 1 / 1 / 2
Minute 4 / 2 / 2
Minute 5 / 1 / 1 / 2
Minute 6 / 2 / 2
Minute 7 / 1 / 1
Minute 8 / 1 / 1 / 2
Minute 9 / 2 / 1
Minute 10 / 1 / 2
Total number
of bubbles / 3 / 15 / 19

3.  Sample answers based on data table:

Beaker A: 0.3 bubbles/minute

Beaker B: 1.5 bubbles/minute

Beaker C: 1.9 bubbles/minute

4.  Sample graph: