Variables:
The independent variables being tested are temperature and germinating versus dry pea seeds. The dependent variable is the amount of oxygen consumed. The control is the respirometer that contains only glass beads.
Data and Observations
Pea Volume: 55 mL
Corrected Difference in the amount of Oxygen Consumed (mL)
Observations: It was noted that germinating peas showed the greatest change in water volume at twenty five degrees Celsius. At ten degrees Celsius, the change in water volume was less. In contrast, dry peas showed very little change at both temperatures.
Variables:
The independent variables being tested are temperature and germinating versus dry pea seeds. The dependent variable is the amount of oxygen consumed. The control is the respirometer that contains only glass beads.
Data and Observations
Pea Volume: 55 mL
Corrected Difference in the amount of Oxygen Consumed (mL)
Observations: It was noted that germinating peas showed the greatest change in water volume at twenty five degrees Celsius. At ten degrees Celsius, the change in water volume was less. In contrast, dry peas showed very little change at both temperatures.
- Graph 5.1
The independent variable is time (x-axis).
The dependent variable is the amount of oxygen consumed (y-axis).
5. Table 5.2
8. Graph 5.2
Analysis of Results
1. The first hypothesis being tested is the effect of germinated versus non-germinated pea seeds on respiration rate. It was predicted that germinated seeds would show higher rates of respiration. This is because germinated seeds are not dormant and probably require huge amounts of oxygen in order to grow and develop. The second hypothesis being tested is the effect of warm versus cold temperatures. It was predicted that warmer temperatures would have higher rates of respiration. At colder temperatures, chemical reactions (i.e. cellular respiration) go at smaller rates. As the temperature increases, the rate of the chemical reaction increases.
2. Conditions that remained constant were water volume, water temperature, and pea volume. It is important for water volume and temperature to remain constant in order to prove that the decrease in volume only occurred by the loss of oxygen in the respirometer. According to the gas law, a change in temperature could change the volume of oxygen gas. The volume of the peas needed to remain constant so that the volume of oxygen in each respirometer was equal at the start of the experiment.
3. Graph 5.1
4. As time increased, the amount of oxygen consumed increased. As time went on, the germinating pea seeds consumed more oxygen gas. This is because the germinating pea seeds needed more oxygen at time increased.
5. Table 5.2
6. The readings from the peas could be altered by changes in temperature, pressure, or the formation of potassium carbonate in the respirometers. The readings from the peas are not affected by such problems and thus form the control group of the experiment. By subtracting the control group from the germinating and dry pea readings, the readings take into account temperature and pressure changes. Thus, the data becomes more accurate with the corrected differences.
7. Germinated peas are more active on the cellular level than non-germinated pea seeds. This is because non-germinated pea seeds are dormant and do not require great amounts of energy in order to function. Thus, germinated peas have higher rates of respiration in order to take in more energy.
8. Graph 5.2. The graph is correct for the data because as temperature increases, the amount of consumed oxygen increases. It is predicted that the graph of the data would be linear.
9. The purpose of the potassium hydroxide is to react with the carbon dioxide produced by the cellular respiration in the pea seeds. When carbon dioxide reacts with potassium hydroxide, gas is removed from the respirometer and water then begins to move into the pipette. If carbon dioxide did not react with the potassium hydroxide, then volume of gas in the respirometer would be equal before and after cellular respiration. The removal of carbon dioxide shows the amount of oxygen that was consumed by the reaction.
10. The vial had to be completely sealed to insure that water did not enter the respirometer and that oxygen gas did not leave. If the vial was not sealed, the two substances would enter and exit the respirometer and ruin the results. Also, using the stopper separates the external and internal pressure forces acting on the fluids. By doing this, water travels from the high pressure area outside into the low pressure area inside.
11. It would be expected that rates of respiration would be lower for the reptile at ten degrees Celsius. Reptiles are dependent on outside temperatures in order to survive. In contrast, mammals are able to maintain homeostasis despite temperature changes. Thus, because reptiles are dependent on environmental temperatures, reptiles would have lower respiration rates at ten degrees Celsius.
12. The higher rate of respiration in the mammal would occur at twenty-one degrees Celsius. As temperature increases, the rate of the reaction increases. Therefore, at higher temperatures, the rate of respiration would be greater. At ten degrees Celsius, it would be predicted that the rate of respiration would be very low.
13. The water moved into the pipette because of the pressure differences. When the pressure changes in the respirometer (because of the removal of carbon dioxide), an area of lower pressure is created inside the respirometer. The pressure is higher outside and thus, the water moves into the pipette in order to reestablish equilibrium.
14. The experiment would have four respirometers with equal volumes of peas that have been germinating for 0, 24, 48, and 72 hours. The control group would have a respirometer with beads only. It would be predicted that the seeds that have been germinating for longer hours would have higher rates of respiration. This is because with longer germinating periods, pea seeds are more fully developed and chemically active. Thus, the pea seeds with 72 hours of germination would have a higher rate of cellular respiration than the other seeds. The seed with 48 hours of germination would have the second largest respiration rate. It can be seen that as length of germination increases, the rate of cellular respiration increases.
Discussion
According to the data, germinating peas at 25 degrees C had the highest rate of respiration. This is due to many causes. First, germinating peas consume more oxygen than non-germinating peas. Non-germinating peas are dormant and do not require a lot of oxygen in order to survive. This was evidenced in the experimental data were the dry peas had low rates of respiration despite changes in temperature. This proves that dry peas are dormant and do not require much energy in order to survive. In contrast, germinating peas are chemically active. They need more oxygen in order to develop.
Second, at higher temperatures the rate of cellular respiration increases. At lower temperatures, molecules have less kinetic energy and thus do not move around often. Without a lot of movement, the molecules are not able to react at increased amounts. In the experiment, the pea seeds at room temperature had higher rates of respiration. This is mainly because chemical reactions take place at greater rates with an increase in temperature. The hypothesis was thus correct.
One possible source of error includes leaks in the respirometers. Without a full seal, water could leak into the respirometer and change the volume present inside. This could drastically alter the results. Other possible sources of error include changes in temperature and water pressure. However, by using the corrected difference from the bead respirometers, such changes were taken into account. By utilizing the corrected difference, changes in water temperature and pressure seemed to be mitigated.
By using the experimental data, rate of cellular respiration was able to be calculated. The results show that at 25 degrees C, germinating seeds consume .012 mL O2/minute. As more oxygen was consumed, the more carbon dioxide was produced. The carbon dioxide reacted with the potassium hydroxide and led to a decrease in volume. The decrease in volume brought more water into the pipette, which became the method used to measure the amount of oxygen consumed. Overall, this experiment was important in demonstrating the effects germination and temperature have on cellular respiration rates.
Bibliography:
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Campbell, Neil A. and Jane B. Reece. Biology: 6th Edition. San Francisco: Benjamin Cummings, 2002.
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Information from Lab Two: Enzyme Catalysis
- Lecture / Class Notes