Teacher Notes
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Teacher Notes![]() Evolution of Yeast Using a Carbon Dioxide Gas SensorGuided-Inquiry KitMaterials Included In Kit
Dextrose, monohydrate (glucose), C6H12O6•H2O, 50 g
Levulose (fructose), C6H12O6, 50 g Maltose, C12H22O11, 40 g Sucrose, C12H22O11, 40 g Yeast, baker’s, 7 g/pkg, 3 Yeast, brewer’s, 11.5 g/pkg, 2 Yeast, wine, 5 g/pkg, 3 Pipets, graduated, disposable, 60 Test tubes with screw caps, plastic, 60 Additional Materials Required
Water, distilled or deionized†
Water, tap* Beakers, 400-mL, one for each solution and each yeast suspension† Beaker, 1000-mL* Clamps, buret, 2* Magnetic stirrer† Other materials as requested for inquiry (e.g., buffer solutions, NaCl)* Support stand* Vernier® CO2 Gas Sensor with respiration chamber* Vernier® Interface* *for each lab group †for Prelab Preparation Prelab Preparation
Safety PrecautionsAlthough materials for the Introductory Activity are considered nonhazardous, wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Evaluate all student-produced procedures for safety. Wash hands thoroughly with soap and water before leaving the laboratory. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information. DisposalPlease consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All solutions from the introductory activity may be rinsed down the drain according to Flinn Suggested Disposal Method #26b. Sugar solutions may be stored in a lab refrigerator for short periods of time. Sugar water is growth media for microbes, so keep refrigerated and bring to room temperature before resuming the lab. For any chemical not specifically listed in the materials, but used in the inquiry portion of the lab, please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply before students begin experimentation. Lab Hints
Teacher Tips
Answers to Prelab Questions
Sample DataData Table A. Respiration Rates of Yeast Strains {11309_Data_Table_1}
*Reported data is the average of several trials. Determining Respiration Rate{11309_Data_Figure_2}
Guided-Inquiry Design Investigating Sugar Type {11309_Data_Table_2}
Investigating pH
{11309_Data_Table_3}
Answers to Questions
ReferencesSpecial thanks to Vernier Software & Technology for the use of Figure 1, instructions on using the carbon dioxide sensor and the Introductory Activity. Recommended Products |
Student Pages
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Student Pages![]() Evolution of Yeast Using a Carbon Dioxide Gas SensorIntroductionJust as farmers select the most fit plants and animals to breed, bakers, brewers and vintners select specific strains of yeast Saccharomyces spp. to produce the best baked goods and fermented beverages. These strains of yeast are good fermenters, metabolizing glucose into carbon dioxide and ethanol, but each has specific traits to make it desirable for a particular product. The process of selecting individuals with particular characteristics for breeding is called artificial selection. Concepts
BackgroundThrough both natural and artificial selection, hundreds of varieties of yeast have evolved. These yeasts vary in inherited traits that allow them to break down specific types of sugars under certain conditions to produce ethanol and carbon dioxide. Depending on the other ingredients and conditions for fermentation, yeast varieties may have other beneficial traits, such as a high tolerance for heat, acid, alcohol or salt. {11309_Background_Equation_1}
Yeast is used to make dough rise through the production of carbon dioxide gas. In beer and wine making, the ethanol stays in solution while most of the carbon dioxide gas comes out of solution and into the air. Carbohydrates—including sugars—must be converted to glucose before respiration can occur. Enzymes facilitate this conversion by reducing the amount of energy required to start the hydrolysis reaction. Sucrose is a disaccharide that reacts with water to form glucose and fructose. Sucrose and water are both stable molecules that require a high amount of energy to react. An enzyme called sucrase binds to sucrose, changing its shape and destabilizing the molecule. Once destabilized, sucrose more easily reacts with water. An organism must have a set of enzymes to digest different types of carbohydrates into glucose. A specific enzyme breaks down a certain type of carbohydrate. The evolution and artificial selection of organisms with differing sets of enzymes allows for the utilization of different food sources. This variety reduces competition by enabling organisms to occupy different niches in the same ecosystem. Therefore having a specific, but different, set of enzymes can be beneficial to survival where food is scarce. Yeasts are organisms that vary in the amounts and types of enzymes they have, which allows them to utilize different types of sugars or other food sources. Cultivators have capitalized on this variation and have selectively bred yeast varieties to accomplish different things, such as producing beer, wine or bread. Experiment OverviewThree yeast varieties will be characterized by their ability to convert glucose into carbon dioxide and ethanol. The production of carbon dioxide will be measured over time, giving the rate of respiration. In the introductory activity, a CO2 gas sensor will be used to determine the rate of respiration for baker’s yeast and for brewer’s or wine yeast as each metabolizes glucose. In the inquiry portion, students design and carry out experiments to investigate factors that may influence the respiration of each yeast type. Materials
Baker’s yeast suspension, 3 mL
Brewer’s yeast or wine yeast suspension, 3 mL Glucose solution, C6H12O6, 0.3 M, 6 mL Water, tap Beaker, 1000-mL Clamps, buret, 2 Disposable pipets, graduated, 4 Support stand Syringe Test tube with screw cap, plastic, 15-mL, 2 Thermometer or Vernier® Temperature Probe Vernier® CO2 Gas Sensor with respiration chamber Vernier® Interface Prelab Questions
Safety PrecautionsAlthough materials for the introductory activity are considered nonhazardous, wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. When designing the inquiry portion, include safety precautions and get approval before proceeding. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines. ProcedurePart A. Introductory Activity
Student Worksheet PDF |