To find out and compare the cellular respiration rate at different temperature by using germinating and non-germinating pea seeds.
If the germinating peas are in the cold or the room temperature water, then the rate of cellular respiration will be higher than the rate for the beads or the non-germinating peas. The colder the temperature of the water is, the slower the process of cellular respiration in the peas is.
Independent: Temperature, time
Dependent: Rate of oxygen consumption
* Pencil and paper
* A water bath
* Germinating Peas
* Non-germinating Peas
* Food colouring
* Paper towels
* Potassium hydroxide, KOH pellets
* one-hole test-tube stoppers
* Millimetre rulers
* Non-absorbent cottons
* Laboratory scoop
* 2 Test Tubes
* 2 Pipettes
* Medicine dropper
Temperature: 10 and 25 degree Celsius
Volume of water: 10 mL
30 KOH pellets
3-5 drops of food colouring
Time: 3 minutes for equilibration and 10 minutes (5 times) for the long-term)
1. KOH is strongly alkaline and caustic which might cause blindness. Skin contact was avoided and safety goggles were worn.
2. Pea seeds were placed in water for 24 hours before processing the lab. Some of the peas were kept dry and the wet seeds were kept in damp paper towels until they were germinated. They were checked daily to prevent the seeds from getting mouldy
3. The bath was filled with room temperature water to be prepared for the lab. On the other one, to make it 10 degree Celsius, ice cubes were put into the bath and the temperature was measured with the thermometer.
4. A wad of absorbent cotton was placed in the bottom of each of the vial and 30 KOH pellets were dropped into the cotton for the saturation. 10 seeds were placed in the test tubes and a layer of non-absorbent cotton was placed on top of the KOH solution cotton.
5. For equal volume, beads were added to each of the test tubes with the dormant seeds since dry peas take up less space than the same quantity of germinating peas. The test tubes were capped with the stopper fitted with a pipette, tip pointing outwards.
6. The pipette was put into the water to find out the consumption of the oxygen. The food colouring was dropped into the water by using the medicine dropper.
7. After three minutes, the initial position of the water in the pipette was recorded to the nearest 0.01 ml. Record was checked every 2 minutes for 10 minutes in total.
My hypothesis was that the germinating seeds that are in the cold or room temperature water will have higher rate of oxygen consumption than the non-germinating seeds. I also predicted that as the temperature of the water decreases, the rate of oxygen consumption will be slower as well.
According to the results, the rate of the oxygen consumption of germinating seeds in room temperature (21C1C) was 0.1003 ml/min. On the other hand, the rate of oxygen consumption of germinating seeds in ice water (5C1C) was 0.0039 ml/min. According to the graph, the slope of the rate of oxygen consumption of germinating seeds in room temperature is steeper than the one in ice water. From this, it can be concluded that in room temperature, germinating seeds consume more oxygen than the one in ice water. This means my second part of the hypothesis was correct because the rate of the oxygen consumption of the germinating seeds in room temperature was faster than the one in ice water. So, it means that as the temperature of the water decreases, the rate of oxygen consumption will decrease as well.
My first part of the hypothesis was that germinating seeds will have higher rate of oxygen consumption than the non-germinating seeds. This was supported by the results I have obtained. According to the result, the rate of oxygen consumption for germinating seeds in room temperature (21C1C) was 0.1003 ml/min and the one in ice water (5C1C) was 0.0039 ml/min. Contrarily, the rate of oxygen consumption for non-germinating seeds in room temperature (21C1C) was 0.00061 ml/min and one in ice water (5C1C) was 0 ml/min According to the graph, the slope of the oxygen consumption and the rate of oxygen consumption of germinating seeds in both room temperature and the iced water are steeper than the ones for non-germinating seeds. This means that germinating seeds consumer more oxygen than the non-germinating seeds in both room temperature and ice water.
The reason why germinating seeds consumes more oxygen is that they process faster cellular respiration. The faster cellular respiration occurs, the more oxygen it consumes.
Germinating seeds process faster cellular respiration than non-germinating seeds because germinating seeds contain embryos that grow and process mitosis quickly. Although non-germinating seeds also have alive embryos, they are dormant. Since embryos of the non-germinating seeds are dormant, they do not require lots of energy to process mitosis. So, non-germinating seeds carry out slower cellular respiration thus, consuming less oxygen than the germinating seeds.
The germinating seeds in room temperature consumed more oxygen than the ones in iced water due to the rate of cellular respiration. As the temperature increases, the kinetic energy increases, meaning that the molecules move faster. This causes the cellular respiration to process faster due to faster moving molecules. As the temperature decreases, the kinetic energy decreases, meaning that the molecules to move slower. This causes cellular respiration to process slower due to slower moving molecules. During the lab experiment, the room temperature (21C1C) had higher rate of cellular respiration than the iced water (5C1C). Since the chemical reaction processes in higher rate with a higher temperature, the germinating seeds in room temperature consumed more oxygen than the one in ice water.
Limitations and Suggestion:
Through this experiment, there were some limitations that we faced while performing the lab. First of all, when displacing the seeds and the beads and when reading the water level at the pipette, the measurements might not in accurate due to parallax. This means that the amount of oxygen consumption could have either increase or decreased.
Secondly, the three vials used in the experiment were not fully submerged during equilibration. The purpose of the equilibration or stabilizing was to equilibrate the pressure inside and outside of the vial. So, since vials were not fully submerged into the water in the water bath, the pressure inside the vial and the outside might not be constant, which could alter the amount of oxygen consumption.
KOH, Potassium hydroxide solution might have had contact with the seeds. Since KOH is caustic and corrosive, the solution will damage seeds after contact. If there is a contact, the seeds would not process respiration, which will lead to failure in oxygen consumption. Additionally, some KOH solution might have oversaturated or not saturated the cotton balls enough. This would affect the contact with the seeds, which would affect greatly to the amount of oxygen consumption. If it was oversaturation of KOH solution, it will cause leakage onto the seeds. To improve this situation, specific amount of KOH solution should saturated the cotton balls so that oversaturation does not occur. To prevent the KOH solution from having a contact with the seeds, the inside of the test tube/ vial should be coated with materials that could absorb the KOH solution. If the amount of KOH was too small, it would alter the data drastically. Since the KOH act s removal of CO2 produced after the cellular respiration, if there is too small amount, it would not remove CO2 completely. Therefore, if not enough KOH is added to the cotton ball, not enough CO2 might have been removed, which could affect less oxygen to enter the vial.
There was also not enough Vaseline to cover the stopper. Vaseline was used to seal the vial so that there will not be any leakage of water into the repirometer. However, it it’s not sealed properly with Vaseline, water will enter into vial and oxygen and carbon dioxide will be left in the vial, changing the rate of oxygen consumption
Factors of Errors:
Inconsistent temperature and pressure might have led to imprecise result for the lab. Moving vials, touching vials in anyways might also have led to imprecise result. Cottons having a contact with KOH solution, too much amount of red dye and the different amount of cotton might have also caused error or inaccurate results.
i) Explain how the respirometer works
The purpose of using the respirometer is to measure the oxygen consumption. A basic concept of the gas law, PV=nRt, meaning that the volume of gas is directly proportional to the number of gas molecules, can be applied to uses of respiromter. When there is constant volume and the temperature, pressure changes in the respiromter are directly relative to the change in the amount of gas in the respiromter. That’s why the vials are set to equilibrium in all respirometers for accurate measurement of oxygen consumption without the disturbance of different pressure.
j) Why does the test tube have to be completely sealed around the stopper?
The test tubes have to be completely sealed around the stopper especially when the volume of the air is decreased inside the test tube. This would lead to water suction into the pipette so that evident water change can be measured. By sealing around the stopper, the water will not go into the respirometer and prevent the oxygen from leaking out. The sealing of the test tubes segregate the internal and external pressure forces on fluids, letting water travel from high pressure (outside of the test tube) to low pressure (inside of the test tube). If the test tubes were not completely sealed around the stopper, the oxygen and the water will move in and out freely, preventing the measurement of oxygen consumption.
k) Explain why water moves into the bent tube of the respirometer.
The water moves into the bent tube of the respirometer because of the changes in pressure. The pressure that is inside the respiromter changed due to the removal of CO2. The internal part of the respiromter has lower pressure than the external part because the amount of gas inside the respirometer decreased due to removal of CO2. According to diffusion, the water moves from higher pressure to lower pressure. Since the pressure is higher outside of the test tube, the water moves into the pipette, where it has a lower pressure, and establishes equilibrium for constant pressure.
l) Why does food colouring move in opposite directions? Explain why allowing the respirometer to stabilize before closing the pinch clamp would avoid this problem?
In cold water, the food colouring moved toward the respirometer because the pressure in the vial was lower than the outside pressure. However, in warmer water, the food colouring moved away from the respirometer because the pressure inside the vial was higher than the pressure outside one. To avoid this problem, respirometer should stabilize so that the pressure inside and outside of the vial can stabilize. So during the experiment, the food colouring would move one way toward the respirometer, instead of moving both direction
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