Respiration Lab BIO 101

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Northern Virginia Community College *

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101

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Biology

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Dec 6, 2023

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BIO 101 Lab: Measuring Cellular Respiration Objective:____________________________________________________________ ● To determine and compare the rate of aerobic cellular respiration in several organisms by measuring CO 2 production. Background:___________________________________________________________ All living cells must spend energy in the form of ATP to carry out their life functions. All cells (both autotrophs and heterotrophs) make this ATP by a process called cellular respiration, which releases energy stored in the chemical bonds of carbohydrates (and other biochemicals) as they are broken down and oxidized. Cellular respiration is a controlled, stepwise, enzyme-catalyzed metabolic process. While some cells can respire in the absence of O 2 (anaerobic respiration), most cells of plants and animals perform only aerobic respiration, which is summarized by the following equation: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + ATP In other words, the above equation shows that when glucose is broken down and oxidized in the presence of oxygen gas to carbon dioxide gas and water, energy is released in the forms of both ATP and heat. By measuring the production of carbon dioxide, one can demonstrate that aerobic cellular respiration is occurring. In this experiment you will measure the production of CO 2 in three aquatic organisms that are ectothermic (obtain heat from their surroundings). The amount of CO 2 produced per unit time is a measure of the rate of cellular respiration. When cellular respiration is termed a controlled process, this means that its rate varies according to the need for energy (ATP and/or heat). Different organisms have different energy requirements (e.g., because they have different activity levels or need to generate different amounts of heat). Even in one organism (e.g., the human being), more energy must be released during periods of great activity than during relaxation or sleep. Materials:___________________________________________________________ • 4 small beakers (250mL) • leeches, fish and Elodea • phenolphthalein • NaOH • pH strips • balances • aerated water • graduated cylinders • 4 small flasks (125 mL) Procedure:___________________________________________________________ 1. Label four beakers 1 through 4. Using a graduated cylinder, add 100 mL of aerated distilled water to each of the four beakers. beaker organism 1 fish 1

2 leech 3 plant 4 none 2. Weigh each beaker with its water to the nearest 0.001 g and record the weights in the Weight of Organisms Data Table, Column (A). This is your tare weight. 3. Put one organism into each beaker as indicated below. Be sure to use at least 8 cm of Elodea. Weigh each beaker again and record their weights with the organisms in the Weight of Organisms Data Table, Column (B). 4. Subtract the tare weight from the total weight to determine the organism's weight in grams. Record your results in the Weight of Organisms Data Table, Column (C). 5. Watch the leech. If it tries to exit the water, push it back under the water using a gloved finger. Note the time (0 time). 6. Label four 125-mL flasks with numbers l through 4. 7. After one hour, return all the organisms to their respective tank or container – be careful to transfer as little water as possible when returning the organisms. Use a graduated cylinder to measure 25 mL of the water from beaker 4 into flask 4. 8. Rinse the cylinder and Repeat step 7 for beakers 3, 2, and 1. DO NOT DISCARD the remaining water in the beakers until after you have collected all of your data as directed below. During the hour, each organism releases CO 2 into the water, which makes the water more acidic. When CO 2 dissolves in water, it lowers the pH as shown by the following equation: CO 2 + H 2 O H 2 CO 3 H + + HCO 3 – Follow steps 9 –11 below to neutralize the water in each flask by adding a base, sodium hydroxide (NaOH). (The OH – of NaOH combines with the H + to form water. Removal of the H + from solution raises the pH to 7.) The addition of a pH indicator (phenolphthalein) allows you to see the point at which the solution reaches the neutral pH. The more CO 2 in a solution, the more NaOH will be required to get to the end point (become basic). 9. Take the flask containing 25 mL of water from beaker 4 and place it on a white background. 10. Add 4 drops of phenolphthalein and swirl the flask to mix thoroughly. 11. Slowly add NaOH, drop by drop, to the water in the flask. COUNT the number of drops as they are added, swirling after each drop, until the solution turns and remains a faint pink color. Wait 10 seconds. If there is still a faint, but definite pink color, you have reached the end point. If the color disappears, you are very near the end point and should cautiously continue to add drops of NaOH. Record the total number of NaOH drops added in the Rate of CO 2 Production Data Table, Column A. 2

12. Using 25 mL of water from beakers 3, 2 and 1, repeat the procedures outlined in steps 9–11. 13. Multiply the number of drops of NaOH by 4 to determine the number of drops you would have had to add to your total volume of 100 ml. Convert the number of drops to ml by dividing by 20 (1 mL = 20 drops). Record your results in the Rate of CO 2 Production Data Table, Column C. 14. Use the following equation to calculate the rate of CO 2 production for each organism in µ moles/hr/g. Enter your calculated results in the Rate of CO 2 Production Data Table. [mL NaOH (expt.) – mL NaOH (control)] × 2.5 µ moles NaOH/mL* 1.0 hour × weight of organism (g) *µ moles/mL is the concentration unit of the NaOH you added (you need not understand this). 15. Make a graph of the rate of respiration versus organism. Table: Weight of Organism Table: Rate of CO 2 Production Organism A Drops NaOH/25mL B = 4 x A Drops NaOH/100mL C = B ÷ 20 mL Weight of organism Rate of respiration (µmol CO 2 /hr/g) fish 52 208 NaOH/mL 10.4mL 10.15 g 0.79 leech 54 216 NaOH/mL 10.8mL 1.83 g 4.92 plant 40 160 NaOH/mL 8mL 2.31 g 0.87 none 36 144 NaOH/mL 7.2mL 0 g 0 3 Organism A Tare weight: beaker + water (g) B Weight with organism (g) C (B-A) Weight of organism (g) 1. fish 215.68 g 225.84 g 10.15 g 2. leech 230.98 g 234.91 g 1.83 g 3. plant 227.84 g 230.15 g 2.31 g 4. none 222.58 g 222.58 g 0 g

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Answer the following questions: 1. Relate the amount of CO 2 produced to cellular respiration. The fish did the least, and then the plant, and finally, the snail did the most 2. Why was the amount of CO 2 divided by the weight of the organism? Dividing by weight helps compare fairly because bigger organisms produce more CO2 just because they're larger 3. Do your results support the hypothesis that organisms respire at the same rate? no 4. Discuss and compare the rates of cellular respiration of the organisms and explain any differences in the rates you saw. The observed organisms had different respiration rates. The plant's rate was pretty low because it combines respiration with photosynthesis. the fish was massive compared to other fishes, and the snail had the highest rate due to their animal metabolism. These differences result from their distinct biological characteristics and metabolic needs. 5. What factors with these specific organisms might make comparisons difficult? Comparisons between these specific organisms may be complicated by differences in their metabolic processes, size, sensitivity to environmental conditions, unique physiological traits, and sources of glucose. 6. How might your rate of cellular respiration compare? Explain. My rate of cellular respiration would be intermediate compared to plants and highly active animals like fish. It varies based on factors such as physical activity, metabolic rate, age, health, diet, and environmental conditions. 7. How would an increase in physical activity affect the amount of CO 2 produced? When you do more exercise or physical activity, your body needs more energy. To make this energy, your body breathes in more oxygen and breathes out more CO2. So, increasing physical activity means you produce more CO2 because your body is working harder to give you the energy you need. 8. Predict the effects of a temperature increase on the amount of CO 2 produced by the organisms. An increase in temperature generally leads to more CO2 production in organisms. This is because higher temperatures usually boost metabolic rates, enzyme activity, and oxygen demand, all of which contribute to increased respiration and, consequently, more CO2 being released. 9. Why did you use aerated water in the beakers? 4

Aerated water contains oxygen. It's used to make sure there's enough oxygen for organisms that need it to breathe. 10. What was the function of the control? (think about its role in the equation) The control serves as a standard for comparison. It shows what happens without any changes or treatments. 11. Write the equation which shows how the addition of CO 2 makes the water acidic. CO2 + H20 -> H2C03 -> H+ +HCO3 12. Summarize what you showed in this experiment. In this experiment, we observed the respiration rates of different organisms (a plant, a fish, and a snail) and analyzed how they were influenced by factors such as metabolic activity, size, and metabolic diversity. 13. What was the source of glucose for each of the organisms? Plant: Photosynthesis, using sunlight, carbon dioxide, and water. Fish: Obtained from their diet, usually by consuming other organisms. Snail: Also acquired from their diet, primarily by eating plant material. 5

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