Cellular respiration lab PDF

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Cellular Respiration PRE-LAB QUESTIONS 1. Why is cellular respiration necessary for living organisms?

Cellular respiration creates ATP. Almost all the processes which happens in the body requires ATP to grow, divide, fight against attacks from foreign particles. Without cellular respiration the cells will die.

2. Why is fermentation less effective than respiration?

For each molecule of glucose fermentation produces only 2 ATP molecules.

3. What is the purpose of glycolysis?

Glycolysis breaks down glucose into two pyruvate molecule and this can be used in either aerobic respiration or anaerobic respiration depending on the need of the cell of the organism.

4. How many ATP molecules are produced in aerobic respiration? How many ATP molecules are produced during fermentation and glycolysis?

Aerobic respiration produces up to 38 ATP molecules from one glucose molecule. Fermentation produces about 2 ATP molecules from one glucose molecule and glycolysis also produces 2 ATP molecules.

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Cellular Respiration EXPERIMENT 1: FERMENTATION BY YEAST Data Tables Table 1: Yeast Fermentation Data Initial Gas Height (mm)

Tube

Final Gas Height (mm)

Net Change

1

7

8.5

1.5

2

7

9

2

3

5

5

0

4

4

4

0

5

5

6

1

Post-Lab Questions 1. Include your hypothesis from Step 1 here. Be sure to include at least one piece of scientific reasoning in your hypothesis to support your predictions. Fermentation results in the production of carbon dioxide this causes an increase in the final gas height. The reason for this is that the natural sugars present causes fermentation leading to the production of carbon dioxide. 2. Did you notice a difference in the rate of respiration between the various sugars? Did the artificial sugar provide a good starting material for fermentation? There is a difference in fermentation rate between different sugars. The artificial sugars did not provide a good starting material for fermentation because there was no change in height off the gas. 3. Was anaerobic fermentation occurring? How do you know (use scientific reasoning)? There was aerobic fermentation occurring because there is an increase of height in the

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Cellular Respiration gas column. This shows that aerobic fermentation is occurring because of the production of carbon dioxide. 4. If you observed respiration, identify the gas that was produced. Suggest two methods you could use for positively identifying this gas. The gas that was produced was carbon dioxide. You can identify the gas by looking for the bubble formation and the change of height in the gas column. 5. Hypothesize why some of the sugar or sweetener solutions were not metabolized, while others were. Research the chemical formula of Equal® and Splenda® and explain how it would affect yeast respiration. The enzyme theobromine stopped some of the sugars from being metabolized. Equal is not made of sugar, sot his will affect yeast respiration. Equal is unable to be metabolized. 6. How do the results of this experiment relate to the role yeast plays in baking? Fermentation in yeast produces ethanol and CO2. The CO2 allows the bread to rise. 7. What would you expect to see if the yeast cell metabolism slowed down? How could this be done? Cooling is down. Heat speeds up metabolism while cold decreases it. 8. Indicate sources of error and suggest improvements (for example, what types of controls could be added?). The temperature of the surroundings may not have been the same on the two days, or even on one single day they may have fluctuated.

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Cellular Respiration EXPERIMENT 2: AEROBIC RESPIRATION IN BEANS Data Tables Table 2: Bromothymol Blue Color Change Over Time for Pinto Beans Time

Pre-Soaked Pinto Beans

Dry Pinto Beans

0 min

Blue

Blue

Blue

30 min

Blue-green

Blue

Blue

60 min

Green

Blue

Blue

90 min

Bright green

Blue

Blue

120 min

Bright green

Blue

Blue

150 min

Light green

Blue

Blue

180 min

Yellow green

Blue

Blue

Yellow

Blue

Blue

24 hours

No Pinto Beans

Table 3: Bromothymol Blue Color Change Over Time for Kidney Time

Pre-Soaked Kidney Beans

Dry Kidney Beans

No Kidney Beans

Blue

Blue

Blue

30 min

Blue green

Blue

Blue

60 min

Green

Blue

Blue

90 min

Bright green

Blue

Blue

120 min

Bright green

Blue

Blue

150 min

Light green

Blue

Blue

180 min

Yellow green

Blue

Blue

Yellow

Blue

Blue

0 min

24 hours

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Cellular Respiration Post-Lab Questions 1. How did the color of the bromothymol blue solution in each beaker change over time in each condition?

The color changes from blue to green and green to yellow in the beaker with germinating beans, in the beakers with no beans and unsoaked beans it remains blue.

2. What is the mechanism driving the bromothymol blue solution color change?

In the case of soaked beans, the carbon dioxide is releasing into the water which turns it into a weak acid, so this creates a color change in the bromothymol, but in dry beans, there is no respiration, so there is no color change.

3. What can be inferred from the color change of the bromothymol blue solution?

We can infer that there is acid present in the beaker containing soaked beans, this is due to the release of co2 during cellular respiration.

4. What evidence do you have to support that cellular respiration occurred in the beans? Explain your answer.

Co2 was released during respiration in the water containing soaked beans. This created a reaction forming carbonic acid. Bromothymol blue reacted with this acid to change its color from blue to green and green to yellow according to increasing time. This is how we know that cellular respiration occurred in the beans.

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Cellular Respiration 5. What are the controls in this experiment, and what variables do they eliminate? Why is it important to have a control for this experiment?

In this experiment dry kidney beans and no kidney beans in beaker act as the control. It is important to have a control because we can differentiate between the change in the reaction due to the release of CO2 in this experiment, because there is no respiration in the control.

6. If this experiment were conducted at 0 °C, what difference would you see in the rate of respiration? Why?

If the experiment was conducted at 0 degrees Celsius the rate of respiration would be slow. This is because cold or low temperatures inhibit respiration. The color change as well as carbon dioxide release would be slow as compared to at room temperature.

7. Would you expect to find CO2 in your breath? Why?

Yes, the carbon dioxide we breathe out is a product of cellular respiration from the foods that we eat. The carbs, fat, and proteins we eat are transformed into glucose to give energy to our cells.

8. What else could you incorporate into this experiment to verify that the gas is responsible for the color change? Design an experiment that shows the steps required.

A change in temperature could be incorporated into this experiment to verify that the gas is responsible for the color change.

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Cellular Respiration

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