Name: __________________________________ Date: __________ Period: _________ Yeast in Action Lab Unit 1: Cellular Organization, Biology Background (from CK12.org): Why do you need food? - The main reason you need to eat is to get energy. Food is your body's only supply of energy. However, this energy must be converted from the apple (or any other food you eat) into an energy source that your body can use. The process of getting energy from your food is called cellular respiration, and most of this process happens in the mitochondria. What is Cellular Respiration? - How does the food you eat provide energy? When you need a quick boost of energy, you might reach for an apple or a candy bar. But cells do not "eat" apples or candy bars; these foods need to be broken down so that cells can use them. Through the process of cellular respiration, the energy in food is changed into energy that can be used by the body's cells. Initially, the sugars in the food you eat are digested into the simple sugar glucose, a monosaccharide. Recall that glucose is the sugar produced by the plant during photosynthesis. The glucose, or the polysaccharide made from many glucose molecules, such as starch, is then passed to the organism that eats the plant. This organism could be you, or it could be the organism that you eat. Either way, it is the glucose molecules that holds the energy. ATP - S pecifically, during cellular respiration, the energy stored in glucose is transferred to ATP (Figure at right). ATP, or adenosine triphosphate, is chemical energy the cell can use. It is the molecule that provides energy for your cells to perform work, such as moving your muscles as you walk down the street. But cellular respiration is slightly more complicated than just converting the energy from glucose into ATP. Cellular respiration can be described as the reverse or opposite of photosynthesis. During cellular respiration, glucose, in the presence of oxygen, is converted into carbon dioxide and water. Recall that carbon dioxide and water are the starting products of photosynthesis. What are the products of photosynthesis? The process can be summarized as: glucose + oxygen → carbon dioxide + water. During this process, the energy stored in glucose is transferred to ATP. Energy is stored in the bonds between the phosphate groups (PO4-) of the ATP molecule. When ATP is broken down into ADP (adenosine diphosphate) and inorganic phosphate, energy is released. When ADP and inorganic phosphate are joined to form ATP, energy is stored. During cellular respiration, about 36 to 38 ATP molecules are produced for every glucose molecule. Cellular respiration involves many biochemical reactions. However, the overall process can be summed up in a single chemical equation: C6H + energy (stored in ATP) 12O 6 + 6O2 → 6CO2 + 6H2O Background Questions: ● What is the function of cellular respiration? ● Do plant cells respire? If so, why? ● What kinds of molecules are used for cellular respiration? Give specific examples. ● What is ATP? ● What is the use of ATP? Give three examples of how ATP is used in the cell. ● How much usable energy is extracted from one glucose molecule? Lab Introduction: In this laboratory activity, you will be investigating the production of gas by yeast. As you may know, yeast are unicellular fungi that are often used in the production of foods, such as bread and alcoholic beverages. Certain strains of yeast can also cause skin infections in humans. We will conduct two experiments to determine how the concentration of sugar in a solution and temperature affects the rate of cellular respiration in yeast. Materials: ▪ Yeast suspension ▪ Sucrose solutions of various concentrations ▪ Graduated cylinders ▪ Electronic scale ▪ Timer ▪ ▪ ▪ ▪ Safety goggles Water at various temperatures Test tubes Ruler Sugar Concentration Procedures & Data Temperature Procedures & Data Hypothesis As the concentration of sugar ____________, then the Hypothesis As the temperature ____________, then the rate of rate of cellular respiration will ____________, cellular respiration will ____________, because_____________________________________. because_____________________________________. Therefore, I will observe _______________________. Therefore, I will observe _______________________. Experimental Design: Experimental Design: Independent Variable: _________________________ Independent Variable: _________________________ Dependent Variable: Dependent Variable: ___________________________ ___________________________ Controls (List three): __________________________ Controls (List three): __________________________ ___________________________________________ ___________________________________________ Procedure: 1. Label four test tubes 1-4. 2. Add 5 ml of yeast suspension to each tube. 3. Make sugar solutions: ▪ Do not add any sugar to Tube 1 (0% sugar). ▪ Add 0.25 g of sugar to Tube 2 (5% sugar). ▪ Add 0.5 g of sugar to Tube 3 (10% sugar). ▪ Add 1.0 g of sugar to Tube 4 (20% sugar). 4. Cover the tube with your thumb and mix each solution until the yeast is dissolved. 5. When the sugar is dissolved, start timing the reaction. Record the time in the data table below in the “Time Start” column. 6. At 15 minutes, measure the amount of bubbles at the top of the tube in centimeters and record it on the data table below. Record the height of bubbles in the data table below in the “Height of Gas Bubble” column. Procedure: 1. Label four test tubes 1-4. 2. Add 5 ml of yeast suspension to each tube. 3. Add 0.5 g of sugar to each tube (10% sugar). 4. Cover the tube with your thumb and mix each solution until the yeast is dissolved. 5. When the sugar is dissolved, start timing the reaction. Record the time in the data table below in the “Time Start” column. 6. Immediately place each tube in the water bath for the correct temperature. ▪ Tube 1: ice bath (0°C) ▪ Tube 2: room temperature (25°C) ▪ Tube 3: warm water (40°C) ▪ Tube 4: boiling water (100°C) 7. At 15 minutes, measure the amount of bubbles at the top of the tube in centimeters and record it on the data table below. Record the height of bubbles in the data table below in the “Height of Gas Bubble” column. Individual Data Table: Independent Variable: Tube Number Condition Time Start Final Height of Gas Bubbles 1 2 3 4 Class Data Tables: Sugar Concentration Class Data Sugar Conc. (%) Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Group 3 Group 4 Group 5 Group 6 Group7 Average 0 5 10 20 Temperature Class Data Temp. (°C) 0 25 40 100 Group 1 Group 2 Group7 Average Using a line graph, show the relationship between the concentration of sucrose and the height of the bubbles. Include a title on the x and y-axis. Include the proper units and make sure your table is neat and organized. Be sure to include a title, legend, axis labels, and proper units.  Sugar Concentration Temperature Analysis Questions: 1. Was there any measurable gas being produced in tube 1? Why did this tube have to be included in the investigation? 2. How did each variable affect the rate of respiration? Why? Variable: Variable: Pattern: Pattern: Possible Explanation: Possible Explanation: 3. Yeast is used in making breads and other baked goods that need to rise. Sugar is commonly added to dough as food for yeast. What would happen if you mixed dough together for a loaf of bread but did not add any sugar? Explain your answer.