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Cellular Respiration Experiment

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This experiment tested the hypothesis that there is no difference between before exercise and after exercise in terms of cellular respiration rates. The purpose of this experiment is to compare the rates of cellular respiration before and after vigorous exercise. During cellular respiration, glucose is broken down into CO2 (carbon dioxide). As CO2 (carbon dioxide) is bubbled through water, H2CO3 (carbonic acid) is formed. Because H2CO3 (carbonic acid) is a weak acid and dissociates in water, it forms HCO3- and H+ ions. As a basic solution is partially neutralized by an acid, phenolphthalein turns clear. Measuring the relative rates of the production of carbon dioxide before and after exercise can help us compare the rates of cellular respiration. We can estimate the rates of cellular respiration by measuring how much time it takes for the phenolphthalein to change color because the carbon dioxide we exhale would react with the water in the solution to form carbonic acid. Then the carbonic acid would neutralize the NaOH in the solution and would turn colorless when enough acid …show more content…

The “before” and “after” samples were produced with the same concentrations at the same time. First, 220 ml of H2O is measured in a graduated cylinder and poured into an Erlenmeyer flask. Then, 5 drops of 10% sodium hydroxide and 3 drops of phenolphthalein is added and swirled gently together. Next, the solution is aliquoted into two 250 ml Erlenmeyer flasks with 100 ml in each flask. The subject inserted a straw into the solution of one flask and blown gently through the straw. The observer watched carefully and recorded the number of seconds it took for the solution to change from pink to clear. The resting time is recorded and the subject exercised vigorously for five minutes. The subject repeated the blowing process through the straw using the second flask and the observer recorded the time it took for the solution to turn

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