Lab #5: Cellular RespirationAnanya, Bonnie, Jiaqi,

Neha, and Susie

Purpose of this Lab The purpose of this lab was to determine the rate of cellular respiration in germinating peas by measuring the consumption of oxygen at various temperatures.

How can the rate of cellular respiration be measured?

- By measuring the amount of glucose consumed- By measuring the amount of oxygen consumed- By measuring the amount of carbon dioxide produced

How did you measure rate of cellular respiration in this lab?

- The rate of cellular respiration of germinating peas was found by measuring the oxygen that was consumed over time

Relevance of the Lab to Class Content● Cellular Respiration

○ C₆H₁₂O₆ + 6O₂ ⟶ 6CO₂ + 6H₂O + Energy (ATP + energy)

● Plants use cell respiration when there is a lack of light to perform cell work

● The rate of cellular respiration accelerates as enzymes begin using the stored food supply to generate ATP.

Other concepts within the Lab - Gas Law: PV = nRT- Respirometer works in accordance to the gas law:

Experimental Design DiagramIV: Type of peas (germinating and dry)

DV: Pressure of gas

Levels of IV: 1

# of trials: 6

Control: Beads Constant: Temperature, volume of peas, cotton balls

Hypothesis - Null Hypothesis: The rate of cellular respiration will be the same in the

germinating peas and the non-germinating peas and beads and the rate of cellular respiration will be the same at 10 degrees C and 25 degrees C

- Our hypothesis: The rate of cellular respiration will be greater in germinating peas than in non-germinating peas, and greater at 25 degrees C.

1. Measure 25 germinating peas2. Measure 10 dry peas + enough

glass beads for the same volume

3. Measure glass beads with a volume = volume of the germinating peas

4. Place 10 drops of KOH on absorbent cotton, then put rope

cotton over

***Optional Step: place food dye on tip of respirometer to see bubble

better

5. Equilibrium step 6. Check water temperature (10C or 25C) 7. Place respirometers in water, measure every 5 min

Procedure

Presentation of Data - Personal Data

Time (minutes)

10℃ Germinating Peas (mL O2)

10℃ Dry Peas (mL O2)

0 minutes 0 mL 0 mL

5 minutes N/A N/A

10 minutes -0.24 mL 0.11 mL

15 minutes -0.32 mL 0.14 mL

20 minutes -0.42 mL 0.18 mL

Personal Data (Corrected Difference)

Time (minutes)

10℃ Germinating Peas (mL O2)

10℃ Dry Peas (mL O2)

0 minutes 0 mL 0 mL

5 minutes N/A N/A

10 minutes 0.73 mL 0.39 mL

15 minutes 0.74 mL 0.27 mL

20 minutes 0.74 mL 0.25 mL

Personal Data (Raw Data)

Presentation of Data - Class Data

Time (minutes) 10℃ Germinating Peas (mL O2)

10℃ Dry Peas (mL O2)

25℃ Germinating Peas (mL O2)

25℃ Dry Peas (mL O2)

0 minutes 0 mL 0 mL 0 mL 0 mL

5 minutes -0.27 mL 0.14 mL 0.78 mL 0.14 0.62 mL -0.06

10 minutes -0.33 mL 0.20 mL 1.19 mL 0.64 mL -0.07

15 minutes -0.47 mL -0.20 0.11 mL 1.49 mL 0.69 mL -0.05

20 minutes -0.52 mL 0.15 mL 1.76 mL 0.67 mL -0.08

Class Data of Corrected Differences (Averages)

***Without Outliers’ Number in GREEN

Group Graph of Germinating Peas

Group Graph of Dry Peas

Error Analysis● Not being able to see the bubble and therefore missing data points● Proper procedure is to read the bottom of the meniscus and groups that

read the top of meniscus have inaccurate data● Moving the vials after the experiment started could have lead to

inaccurate results● Not having the same amount of cotton in each vial● Reading errors● Reading before or after exact time● 0.73 (correct) vs. 7.3 (incorrect), leads to outliers● Unable to maintain temperature in water bath

Conclusion- Germinating peas consumed more oxygen at a faster rate than the non-

germinating peas- Non-germinating peas don’t require as much oxygen therefore having a

lower rate of respiration- Respiration rates increase as the temperature increases- Temperature and respiration rates are directly proportional to each other

Class Discussion

1. Using the ideal gas law and the experience from this lab, give the variables that had to be

controlled for your data.

PV = nRT

P = Pressure changes (DV)V = Volume remains constant

n = moles remains the same as there is the same volume of substance

R = gas constant stays constantT = Temperature was the changed factor (IV)

2. Describe and explain the relationship between the amount of O2 consumed and time based on the

data.

Actual: No trend in data

Supposed to be: As time goes on, the amount of oxygen consumed increases

3. Why was it necessary to correct the readings from the peas with the readings from the beads?

-Numerical comparison of the peas to the beads (control)

-Changes in the environment such as changes in atmospheric pressure affected the rate of respiration, so the readings were corrected so that the results could be

the most accurate

-For a more accurate comparison between the two types of seeds

4. What was the purpose of theKOH in the experiment?

CO₂ + 2KOH ---> K₂CO₃ + H₂O

The purpose of the KOH was to react with the CO₂ and form a precipitate so that it doesn’t mess with the gas

pressure of O₂ entering the device when CO₂ tries to be released.

5. Explain why water moved into the respirometers.

The water moved into the respirometers because O₂ entered the device and due to

lower pressure, the water entered the device

6. If you used the same experimental design to compare the rates of respiration of a 25 g reptile

and a 25 g mammal at 10°C, what resultswould you expect? Explain

Mammals have a higher rate of respiration

Reptiles are cold blooded and can survive in lower temperatures

Mammals will respire more to keep their higher temperature in 10 degrees (produce

more ATP to keep warm)

7. If respiration in a small mammal was studied at both room temperature (25°C) and 10°C, what

results would you predict? Explain

Higher at 10 degrees because they have to respirate more to create more ATP to maintain

the high body temperature

Not as much respiration needed at 25 degrees because it is warmer and not as much temp

regulation needed

8. What results would you expect if you designed an experiment to examine the rates of cellular

respiration with peas that have been germinating different lengths of times: 0, 24, 48, & 72 hours?

Explain.

The peas that were germinating for 0 hours will have the lowest rate of cellular respiration.

As time goes on, rate of cellular respiration increases. The peas that were germinating for 72 hours will have the greatest rate of cellular

respiration.