Cellular Respiration Materials This lab requires advanced preparation.
Per Class
12 100ml beakers 24 Durham tubes 36 test tubes 600ml active yeast solution 300ml grape juice 6 bottles of distilled water 24 transfer pipettes 6 test tube racks 12 stir rods 6 markers 6 bromthymol blue 6 straws 6-18 germinating beans 12 pieces of parafilm
Preparation for Experiment 2 (This needs to sit for 24 hours or more) In this experiment you will determine if germinating beans produce a greater concentration of carbon dioxide than is present in the air. 1. Obtain two test tubes; add 2 ml of tap water and 3 drops of bromthymol blue to each test tube. 2. Put Durnham tubes into the test tubes to make a platform (to keep the beans out of the solution). 3. In tube #1 place 1-3 germinating beans. In tube #2 do not place anything. 4. Cover the test tubes with parafilm, put in a rack, and let sit for 24 hours. 5. Record any color changes and results.
Per Bench
Fermentation 2 100ml beakers 2 Durham tubes ( we used the extra small test tubes 10x75mm) 2 Test tubes (the extra small test tubes need to fit inside) 100 ml yeast solution 50 ml grape juice Distilled water 2 transfer pipettes Test tube rack Marker Stir rods
Cellular Respiration Exp. 1 2 test tubes Bromthymol blue 1 straw Disposable transfer pipettes
Cellular Respiration Exp. 2 (Demonstration) Bromthymol blue 2 test tubes 2 Durham tubes 1-3 Germinating beans 2 pieces of parafilm
Fermentation(20 minutes + 60 minute wait time) In this activity you will see the action of yeast cells on glucose and distilled water. 1. Obtain 2 Durham tubes, 2 beakers (100 ml), and 2 test tubes per group. Label the large test tubes
with your group name. 2. Fill one beaker with half of active yeast solution and half distilled water, and make sure to mix
well with a stir rod. Fill one Durham tube and test tube with this mixture, using a dropper to max-fill. Over a lab sink, invert the Durham tube and place it into the test tube with the distilled water, yeast mixture. No bubble should be in the Durham tube. This might take multiple tries. Carefully, wipe clean the outer test tube and place in a test tube rack. 3. Fill the second beaker with half yeast solution and half grape juice, and stir with a clean stir rod.
Repeat the process in Step 2 to load Durham and test tubes. 4. Place the test tube rack in an incubator (temperature of 37 0C). 5. Allow experiment to incubate for about one hour or longer, then examine and analyze results.
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Cellular Respiration from https://room114.wikispaces.com/Cellular+Respiration
Cellular Respiration and Carbon Dioxide Production: Using Carbon Dioxide as an Indicator of Cellular Respiration Carbon dioxide is a byproduct of cellular respiration. Therefore, we can measure the amount of carbon dioxide as an indicator of cellular respiration. When carbon dioxide combines with water it forms carbonic acid. Bromthymol blue will be used to detect an increase in carbon dioxide concentration. Bromthymol blue is a pH indicator, which turns yellow when the pH decreases or becomes more acidic. In this assignment we will conduct two experiments. Experiment 1 (15 minutes) In this experiment you will determine if your exhaled breath contains a greater concentration of carbon dioxide than is present in the atmosphere. 1. Obtain two test tubes and add 2 ml of tap water with a disposable transfer pipette and 3 drops of bromthymol blue into each test tube. (This should be blue.) 2. Blow into test tube #1 with a straw for 1-3 minutes (careful not to blow too hard and spill). 3. Use a pipette to pump atmospheric air into the second test tube for 2-3 minutes. 4. Record any color changes. (Should turn green in the presence of CO2) Experiment 2 (This needs to sit for 24 hours or more) In this experiment you will determine if germinating beans produce a greater concentration of carbon dioxide than is present in the air. 1. Obtain two test tubes; add 2 ml of tap water and 3 drops of bromthymol blue to each test tube. 2. Put Durnham tubes into the test tubes to make a platform (to keep the beans out of the solution). 3. In tube #1 place 1-3 germinating beans. In tube #2 do not place anything. 4. Cover the test tubes with parafilm, put in a rack, and let sit for 24 hours. 5. Record any color changes and results. (Tube #1 will be green while Tube #2 will remain blue.) 2
Fermentation
Name_______________________
Date_______________
a. Which Durham tube contained more gas? Why? The test tube with grape juice contained more gas. The yeast oxidized the glucose in the grape juice to produce carbon dioxide. b. Did the above experiment require oxygen? The Fermentation experiment does not require oxygen because fermentation is anaerobic. c. What type of gas was captured in the Durham tube? Carbon dioxide gas was captured in the Durham tube. The yeast oxidized the glucose in the grape juice to produce carbon dioxide. d. What is the experimental variable in this experiment (remember the experimental variable is the factor being tested)? Grape juice is the experimental variable. e. What is the dependent variable (remember the dependent variable is what is measured to determine if the experimental variable has an effect)? Carbon dioxide gas is the dependent variable. f. How many molecules of ATP are produced when glucose is metabolized during fermentation? During fermentation, only 2 molecules of ATP are produced. g. Bread is made by mixing flour, water, sugar, and yeast to form dough. Why does the dough rise? What caused all the concavities in a slice of bread? The yeast oxidizes the sugar in the dough and forms bubbles of carbon dioxide causing the dough to rise and air bubbles in the bread. h. What “toxic” substance is produced when vertebrates undergo fermentation? Lactic acid is produced when vertebrates, such as animals undergo fermentation.
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Cellular Respiration and Carbon Dioxide Production a. Record the results of your experiments in the table below. Carbon dioxide production in humans and germinating pea seeds Color of bromthymol blue after experiment Experiment #1 : Human Expiration Tube #1: Exhaled air Yellow Tube #2: Atmospheric air Blue Experiment #2: Germinating Beans Tube #1: Germinating Beans Yellow Tube #2: Atmospheric air Blue
CO2 Concentration (circle appropriate) Increased Increased
No Change No Change
Increased Increased
No Change No Change
b. What is the purpose of tube #2 in experiment 1 and 2? Tube #2 is the control in both experiments. c. What conclusion can you draw from the results of experiment 1? Exhaled breath contains a greater concentration of carbon dioxide then is present in the atmosphere. What conclusion can you draw from the results of experiment 2? Germinating seeds produce a greater concentration of carbon dioxide then is present in the air.
