Cellular Respiration Virtual Lab

Cellular Respiration Virtual Lab Background: All organisms are dependent on a healthy carbon dioxide-oxygen balance. Photosynthesis and cellular respiration are key processes in maintaining this balance. Plants, through the process of photosynthesis, use energy absorbed from sunlight, water, and carbon dioxide to produce sugars and oxygen. Animals and plants, through the process of cellular respiration, use oxygen and sugars to produce carbon dioxide, water, and the energy needed to maintain life. Cellular respiration is the release of energy from carbohydrates and other molecules. Energy from these reactions is used to synthesize ATP molecules which are used to energize a large variety of cellular reactions. Aerobic cellular respiration for the production of ATP occurs in most cells, and requires oxygen for effective completion. The process is therefore said to be aerobic (overall), even though its first stage (glycolysis) is anaerobic (occurs without oxygen). When oxygen is insufficient or unavailable, organisms that are able to must shunt to an anaerobic pathway and perform an alternative process of ATP production. One such anaerobic alternative is known as fermentation. Figure 1. Aerobic Cellular Respiration Glycolysis Glycolysis is the starting point of cellular respiration and occurs in the cytosol of the cell. It is the breakdown of glucose to two pyruvate (pyruvic acid) molecules with the net production of two ATP molecules. Glycolysis is universally found in all organisms and likely evolved before the mitochondrial citric acid cycle and the oxygen-requiring electron transport system used by cells in aerobic cellular respiration. Glycolysis is anaerobic; it does not require oxygen. The Process of Fermentation Fermentation is the anaerobic release of food energy. It occurs when there is no or insufficient oxygen available to support aerobic cellular respiration. Human muscle cells can make ATP with and without oxygen. They have enough ATP to support intense activities, such as quick sprinting, for about 3 seconds. A secondary supply of energy (creatine phosphate) can keep muscle cells energized for about another 10 seconds. To keep functioning beyond that, muscles must then generate ATP by the anaerobic process of fermentation. Glycolysis is the metabolic pathway that provides ATP during fermentation. Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going. In human muscle cells, lactic acid (C3H6O3) is a principal product of fermentation. Fermentation in Microorganisms Various types of microorganisms perform fermentation. Many bacteria carry out lactic acid fermentation. Yeasts are tiny, unicellular fungi that live wherever sugars are plentiful. Yeasts process sugar via aerobic cell respiration, which requires oxygen. If their environment becomes anaerobic, they have an alternative system for sugar processing that does not require oxygen – alcoholic fermentation. Alcoholic fermentation by yeasts is the basis for the production of some foods, such as beer and leavened bread. In an anaerobic environment, yeasts will produce carbon dioxide and ethyl alcohol by alcoholic fermentation. Objectives: These virtual investigations are will allow you to compare the processes of aerobic and anaerobic respiration in order to better understand the similarities and differences between these two processes. What you are to do: 1. Complete Part 1: Open the Snails and Elodea 2. Follow the instructions to complete the virtual lab. 3. Answer the questions on the Lab Worksheet. 4. Complete Part 2: Open the Yeast Fermentation Lab 5. Follow the instructions to complete the virtual lab. 6. Write down a description of the procedures. 7. Answer the questions on the Lab Worksheet. Part 1: Carbon Transfer Through Snails and Elodea Procedures: Follow the steps to the lab given on the screen until you complete all seven (7) steps. You will need to fill in the lab notebook as you go, but you will only be graded on what you put on this assignment sheet. 1. Read through the problem tab. Create your own question for what you are investigating in this experiment. (in question form): What purpose does Elodea play in keeping a snail habitat healthy? 2. Explore the lab to learn what is available to you in your investigation. You must click on each item in the checklist. Describe the materials you will be using in this lab. a. What is Bromthymol Blue? Why is the BTB in the beaker green? It is a chemical indicator that detects the presence of carbon dioxide. The beaker is green because there is already a small amount of CO2 in the solution. b. If snails use lungs to breathe, you can conclude that they release which gas into their environment as a result of respiration? They release carbon dioxide as a result of cellular respiration. c. If Elodea is an aquatic plant, you can conclude that it releases which gas into its environment as a result of photosynthesis? It releases oxygen as a result of photosynthesis. d. What is the purpose of the growth light? It stimulates light conditions if constant light source is needed. e. What is the purpose of the test tube rack cover? Its purpose is for stimulation in dark conditions. f. If no carbon dioxide is present in your test tube it will be a _____Blue_______ color. If a medium amount of CO2 is present, your test tube will be a _____Green__________ color. If a large amount of CO2 is present, your test tube will be _______Yellow___________. 3. Hypothesis: Explain how carbon dioxide (CO2) cycles in aquarium water through snails and Elodea. If I add a snail and elodea to a test tube with bromthymol blue then____the test tube will change in color ___________________________________________________________________ ___________________________________________________________________________ because___there will be a presence of carbon dioxide. _________________________________________________________________ ___________________________________________________________________________ 4. The independent variable in an experiment is the variable which will be altered by you, the scientist. In the case of this experiment, the independent variable will be the number of snails and/or number of elodea plants in each test tube. a. Identify the dependent variable(what you, the scientist, will measure) in this experiment: The amount of carbon dioxide present. You will be using 8 test tubes for this experiment. Fill your test tubes and perform the experiment according to the data chart found below. Data Table 1: First Test Tube Rack – Placed under the growth light: Test Tube with BTB Independent Variables Beginning Color Color Prediction Color Result Tube # 1 (control) No snails, No Elodea Green Green Green Tube #2 2 snails Green Yellow Yellow Tube #3 2 Elodea Green Green Blue Tube #4 2 snails, 2 Elodea Green Green Green Data Table 2: Second Test Tube Rack – Placed under the test tube cover: Test Tube with BTB Independent Variables Beginning Color Color Prediction Color Result Tube # 1 (control) No snails, No Elodea Green Green Green Tube #2 2 snails Green Yellow Yellow Tube #3 2 Elodea Green Green Green Tube #4 2 snails, 2 Elodea Green Green Yellow Conclusions: Complete the following sentences. b. In the test tubes which contained only snails…. The test tube changed to a yellow color, meaning there is a high presence of carbon dioxide being released from the snails. c. In the test tubes which contained only Elodea under the light…. The test tube turned blue. The reaction of photosynthesis in the light caused the plant to intake the carbon dioxide present and release oxygen instead. d. In the test tubes which contained only Elodea in the dark….. The test tube remained the same because there was no light, so photosynthesis could no occur for the elodea plant. e. In the test tubes which contained both snails and Elodea under the light…. The test tube remained green because the two reactions balanced each other out. The snails kept releasing carbon dioxide while the elodea plant kept absorbing the carbon dioxide released by the snail, and then produced oxygen with it. Then the snail absorbed the oxygen and the cycle repeats. Questions: 1) What is the relationship between snails and Elodea? It is a balanced relationship under the right conditions. Where there is oxygen, snails will intake the oxygen and release CO2. The elodea then takes up the carbon dioxide when sunlight is present for photosynthesis to occur, and then the elodea plant releases oxygen. 2) Why did the color of the Bromthymol Blue (BTB) solution change in certain test tubes? It changed to yellow when the snails produced carbon dioxide. It stayed green when there was no reaction, or the elodea plant used up the carbon dioxide and released oxygen for the snail to use and produce carbon dioxide (a balanced cycle). It turned blue when the elodea plant produced oxygen by taking up all the CO2 from the tube, leaving none behind. 3) What was the importance of a control in your experiment? What would you conclude if the color of the solution in the control changed? The purpose of the control experiment was to see that without plants or animals, the carbon dioxide and oxygen levels do not change. If the color changed then that would mean that there is another cause of what makes CO2 and oxygen levels change, excluding snails and plants. 4) When you began the experiment, was there CO 2 in the water? In the test tubes that contained Elodea, where did the CO2 go? Yes, CO2 was first present in the water. In the test tubes that contained elodea, in the ones that had a light source, the CO2 was used up in the plant for energy, and then oxygen was released in replace of CO2. 5) Which gas did the snails release? What observation supports this inference? Carbon dioxide was released. The test tubes with just snails changed to the color yellow, meaning high amount of carbon dioxide. 6) Based on the results of your experiment, explain why you need to add the Elodea to your snail aquarium. You would need to add elodea to the snail aquarium to have a balanced habitat. Without the plants, the snails would not have a reliant source of oxygen to produce energy for itself, and the plants provide that oxygen. Part 2: Yeast Fermentation Lab Procedures: (Check syllabus for format) 1. Obtained all necessary materials 2. Prepared flask 1 with water and yeast 3. Prepared flask 2 with water, yeast and glucose 4. Prepared flask 3 with water, yeast and glucose, and then boiled on heater for 3 minutes 5. Prepared flask 4 with water and glucose 6. Prepared flask 5 with water, yeast and flour 7. Left vials for 24 hours to allow fermentation 8. Recorded and observed gas given off by the flasks. Flask contents Yeast and Water Yeast, Glucose and water Yeast, Glucose, Boiling Water Glucose and Water Yeast, Flour and water Hypothesis: Gas Production? No No Yes No Yes Result: Gas Production? No Yes No No Yes Conclusions: In flask A, respiration did/did not occur Evidence: Respiration did not occur because the balloon did not inflate at all. Reason: There was no glucose for the yeast to intake and cause the reaction. In flask B, respiration did/did not occur Evidence: Respiration did occur because the balloon was full of gas. Reason: Yeast utilized the glucose given and produced CO2 during fermentation. In flask C, respiration did/did not occur Evidence: Respiration did not occur because there was no gas in the balloon. Reason: The water boiled the yeast, causing it to fail to ferment. In flask D, respiration did/did not occur Evidence: Respiration did not occur because the balloon did not inflate at all. Reason: There was no yeast for fermentation to take place, there for causing no reaction. In flask E, respiration did/did not occur Evidence: Respiration did occur because the balloon has some gas in it. Reason: The yeast broke down the flour into glucose and then fermentation occurred, producing CO2. Questions 1. What enzyme is being utilized by the yeast in this process? Zymase. 2. What type of cellular respiration is being conducted by the yeast? What evidence did you use? Aerobic respiration. It takes glucose and oxygen and turns it into carbon dioxide and ATP. Glucose and oxygen were present in the flasks that released gas, and the gas being released was carbon dioxide. 3. What was the purpose of flasks A and E that lacked glucose? To show that cellular respiration of yeast does not occur without glucose. Glucose is an important factor in cellular respiration.