Factors Affecting Respiration Lab



Factors Affecting Respiration Lab

Objective: To investigate factors affecting respiration in an organism.

Background: Living things depend on various nonliving components of their environments to survive and grow. These abiotic factors include sunlight, oxygen, carbon dioxide, availability of water, and temperature. In this experiment, we will be dealing with several abiotic factors: temperature, pH, and availability of food (sugar). Organisms need cellular respiration to get energy their cells can use from their food. This chemical reaction (cellular respiration) requires sugar and (if aerobic respiration) oxygen. Cellular respiration is also controlled by enzymes, which can be affected by the environment. Cellular respiration produces ATP, and two waste products (carbon dioxide and water). We will measure the carbon dioxide production to determine the effect of different factors on cellular respiration.

Pre-lab Questions:

1. What is the purpose of cellular respiration?

2. What form of energy, produced by cellular respiration, can cells easily use?

3. What does aerobic respiration need to occur?

4. What waste products are produced by cellular respiration?

Procedure:

Your group will be assigned ONE factor. ONLY do the procedure for THAT factor!

Hypothesis

Write a hypothesis predicting the effect of the factor your group was assigned on the rate of cellular respiration:

If _________________________________, then______________________________.

Data

Effect of Various Factors on Yeast Respiration

|Factor Affecting Respiration |Measurement of Respiration |

| |Before |After |

|None – Control Group | | |

|High (Hot) Temperature | | |

|Low (Cold) Temperature | | |

|Acidic (Low) pH | | |

|Basic (High) pH | | |

|Different Food Source (Starch not Sugar) | | |

|No Food Source | | |

Analysis:

1. True/False – Cellular respiration can be affected by many factors.

2. Write the equation for cellular respiration. Circle the reactants and draw a square around the products:

_______________________________________________________________

3. If you add yeast, warm water, and sugar to a Zip-loc bag, the bag expands. What waste product of cellular respiration caused the bag to become larger?

_________________________

4. Compare the factors the class completed to the control group. For each factor, write whether respiration decreased, increased, or showed no difference:

a. High Temperature _______________________

b. Low Temperature _______________________

c. Acidic pH _______________________

d. Basic pH _______________________

e. Different Food Source _______________________

f. No Sugar _______________________

5. Cellular respiration is a chemical reaction that requires enzymes. Using what you know about enzymes, why would high temperatures, low temperatures, acidic and basic pH levels change the rate of respiration?

__________________________________________________________________________________________________________________________________

6. Using what you know about starch (a complex carbohydrate made of many simple sugars) and sugar (a simple carbohydrate), why might having starch instead of sugar slow down respiration? __________________________________________________________________________________________________________________________________

7. Why would having no sugar prevent respiration from occurring?

__________________________________________________________________________________________________________________________________

8. What were the optimum temperature and pH conditions for yeast’s cellular respiration, based on the data from this lab? How do you know?

__________________________________________________________________________________________________________________________________

Conclusion

a. Write a conclusion that summarizes the lab, accepts or rejects your original hypothesis, and answers the purpose question of the lab. Discuss any experimental error that may have occurred.

b. Consider each of the factors that were shown to affect the rate of cellular respiration. Which of these factors do you think will have the GREATEST effect? Develop an argument outlining at least 3 points to support your answer.

Factor: Control Group (No Factor)

1. Place 4 teaspoons of sugar and 1 package of yeast in a Ziploc bag.

2. Use the small beaker to measure 200ml of warm water from the front of the room and add to the Ziploc bag. Before sealing the bag, squeeze out as much air as possible.

3. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

4. Set the bag aside for 30 minutes.

5. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Factor: Hot Temperature

1. Prepare the water: Heat water in a large beaker (1000ml) on a hot plate until it reaches 80°C. As the water heats, go on to Step 2. Do not allow the temperature to become too high or the yeast will be killed and no reaction will occur!

2. Place 4 teaspoons of sugar and 1 package of yeast in a Ziploc bag.

3. When water reaches correct temperature, use the small beaker to measure 200ml of warm water and add to the Ziploc bag. Before sealing the bag, squeeze out as much air as possible. Mix the contents.

4. Put the bag in the beaker on the hot plate, making sure it stays submerged for 20 minutes and the temperature remains at 80°C.

5. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

6. Remove and dry the bag off after 30 minutes.

7. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Factor: Cold Temperature

1. Prepare the water: Cool water in a large beaker (1000ml) until it reaches 4°C. As the water cools, go on to Step 2.

2. Place 4 teaspoons of sugar and 1 package of yeast in a Ziploc bag.

3. When water reaches correct temperature, use the small beaker to measure 200ml of cool water and add to the Ziploc bag. Before sealing the bag, squeeze out as much air as possible. Mix the contents.

4. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

5. Put the bag in the beaker of cool water, making sure it stays submerged for 30 minutes and the temperature remains at 4°C.

6. Remove and dry the bag off after 30 minutes.

7. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Factor: Acidic pH

1. Place 4 teaspoons of sugar and 1 package of yeast in a Ziploc bag.

2. Add 100ml of acid to the bag.

3. Use the small beaker to measure 100ml of warm water from the front of the room and add to the Ziploc bag. Mix.

4. Measure the pH of the contents of the bag.

5. Before sealing the bag, squeeze out as much air as possible. Seal the bag.

6. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

7. Set the bag aside for 30 minutes.

8. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Factor: Basic pH

1. Place 4 teaspoons of sugar and 1 package of yeast in a Ziploc bag.

2. Add 100ml of base to the bag.

3. Use the small beaker to measure 100ml of warm water from the front of the room and add to the Ziploc bag. Mix.

4. (Optional) Measure the pH of the contents of the bag.

5. Before sealing the bag, squeeze out as much air as possible. Seal the bag.

6. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

7. Set the bag aside for 30 minutes.

8. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Factor: Different Food Source (Starch)

1. Place 4 teaspoons of corn starch and 1 package of yeast in a Ziploc bag.

2. Use the small beaker to measure 200ml of warm water from the front of the room and add to the Ziploc bag.

3. Before sealing the bag, squeeze out as much air as possible. Seal the bag. Mix the contents.

4. Set the bag aside for 30 minutes.

5. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

6. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Factor: No Sugar Available

1. Place 1 package of yeast in a Ziploc bag.

2. Use the small beaker to measure 200ml of warm water from the front of the room and add to the Ziploc bag.

3. Before sealing the bag, squeeze out as much air as possible. Seal the bag. Mix the contents.

4. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

5. Set the bag aside for 30 minutes.

6. Place the bag on a flat surface and place an index card on top of the bag. Measure the height from the edge of the index card to the table top. Record.

Hypothesis

Write a hypothesis predicting the effect of the factor your group was assigned on the rate of cellular respiration:

If _________________________________, then______________________________.

Data

Effect of Various Factors on Yeast Respiration

|Factor Affecting Respiration |Measurement of Respiration |

| |Before |After |

|None – Control Group | | |

|High (Hot) Temperature | | |

|Low (Cold) Temperature | | |

|Acidic (Low) pH | | |

|Basic (High) pH | | |

|Different Food Source (Starch not Sugar) | | |

|No Food Source | | |

Analysis:

9. True/False – Cellular respiration can be affected by many factors.

10. Write the equation for cellular respiration. Circle the reactants and draw a square around the products:

_______________________________________________________________

11. If you add yeast, warm water, and sugar to a Zip-loc bag, the bag expands. What waste product of cellular respiration caused the bag to become larger?

_________________________

12. Compare the factors the class completed to the control group. For each factor, write whether respiration decreased, increased, or showed no difference:

a. High Temperature _______________________

b. Low Temperature _______________________

c. Acidic pH _______________________

d. Basic pH _______________________

e. Different Food Source _______________________

f. No Sugar _______________________

13. Cellular respiration is a chemical reaction that requires enzymes. Using what you know about enzymes, why would high temperatures, low temperatures, acidic and basic pH levels change the rate of respiration?

__________________________________________________________________________________________________________________________________

14. Using what you know about starch (a complex carbohydrate made of many simple sugars) and sugar (a simple carbohydrate), why might having starch instead of sugar slow down respiration? __________________________________________________________________________________________________________________________________

15. Why would having no sugar prevent respiration from occurring?

__________________________________________________________________________________________________________________________________

16. What were the optimum temperature and pH conditions for yeast’s cellular respiration, based on the data from this lab? How do you know?

__________________________________________________________________________________________________________________________________

Conclusion

c. Write a conclusion that summarizes the lab, accepts or rejects your original hypothesis, and answers the purpose question of the lab. Discuss any experimental error that may have occurred.

d. Consider each of the factors that were shown to affect the rate of cellular respiration. Which of these factors do you think will have the GREATEST effect? Develop an argument outlining at least 3 points to support your answer.

Teacher Notes:

1. Rather than photocopying the entire procedure for all groups, simply make one copy, cut each procedure out, and distribute the assigned procedure to each group.

2. Have a large beaker of warm (50-55°C) water at front for all groups to use (except hot water group.)

3. Leaving the bags in longer than 30 minutes may give better results (if possible)

4. Students may more clearly see the results if presented in bar graph format (on board.)

5.

Materials/Group:

Laboratory Guide Following Dependent on Assigned Factor:

Ziploc Sandwich Bag Hot temperature: Hot water bath, thermometer

Sugar (4 tsp) Cold temperature: Cold water bath, thermometer

Activated dry yeast (1 pkg) Acidic pH: Acid, pH paper (opt)

Stirring Rod Basic pH: Base, pH paper (opt)

Small beaker (250ml) No sugar: Corn starch

Plastic spoon

Index Card

Ruler

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