Cellular respiration is a catabolic reaction that refers to the process of converting chemical energy of organic molecules into a simplify form so it can be used immediately by organism. Glucose may be oxidized completely if sufficient oxygen is available, by the following equation: C6H12O6 + 36 ADP + 36Pi + 6O2(g) 6 H2O + 6 CO2(g) + 38 ATP + heat All organisms, including plants and animals, oxidize glucose for energy. Often, this energy is used to convert ADP and phosphate into ATP. The process of complete oxidation involves glycolysis, Krebs cycle and electron transport chain.
Besides ATP, pyruvate molecules, NADH and FADH2 will be generated to aid the process in aerobic respiration. These chains of reactions happen in cytoplasm. It enters into mitochondrial matrix and releases its final product in the form of energy, water and carbon dioxide. In balancing the process, oxygen is being consumed (Campbell, 2008). In this experiment, Mung bean seeds (Vigna Radiata) were used to measure the rate of cellular respiration. The consumption of oxygen by Mung bean seeds will be measured as weight specific respiration by measuring volume of oxygen consumed, incubation time and weight of Mung bean seeds (ml h-1 kg-1).
A respirator will be used to regulate the external and internal air pressure. Carbon dioxide will be produced as oxygen is consumed therefore to eliminate pressure from effecting the measurement, a chemical will be added that will selectively remove CO2. In order to regulate the external pressure that might force changes in the respirator, a closed system was implemented. Potassium hydroxide, KOH, will chemically react with CO2 by the following equation: (Frankel, 2005) 2 KOH + CO2 K2CO3???H2O There were a few objectives in this experiment.
The first objective is to determine whether the germinating Mung bean seeds go through cellular respiration. Second objective is to find out if different temperature, affect respiration rate and what are the reasons for the differences. It is hypothesize that, the Mung bean seeds incubated at 200C temperature will require more oxygen consumption due to more activity mediated by enzymes. The weight specific respiration of the Mung bean seeds will be greater in the 200 C treatment. By the end of this experiment, we would be able to see the influences of temperature on cellular respiration.
Understands how oxygen demand in relationship to the amount of organic materials available and finally, how KOH absorbs CO2. Methods: To study the effects of temperature, we measured the amount of oxygen being consumed by Mung bean seeds and observed the differences with 100 C and 200 C water bath. There were certain steps that were followed in order to conduct this experiment. In preparation for this experiment, a respirometer was the primary device used. Two respirometers were prepared for two treatments. In one respirometer, two test tubes were needed.
One as the primary experiment and one served as a control. This piece of equipment, consist of a tube with a rubber stopper to seal off the top. The rubber stopper was equipped with a 1ml pipet and a syringe that helped regulate air pressure without allowing air into or out of the tube, as in a closed system (Danyk, 2012). Before the experiment could begin, several steps were taken. In the respirometer, the pipet space was sealed with a drop of 10% KOH, using a dropper. The syringe was used to manipulate and regulate the KOH so that the bottom of the drop, should sit at zero.
Mung bean seeds were added to one test tube and left off 3cm gap from the top rim. Another test tube was filled with absorbent cotton. A few drops of water were dropped to moisten the cotton. Both test tubes were closed with the stopper. Both tubes were incubated into the water bath of 100 C. The same preparation was repeated with a 200 C treatment. When the tubes were placed in the water bath, they were allowed to temperature-equilibrate for 10 minutes. For the 40 minutes subsequently, the reading on the respirometers were recorded every 5-minute interval, for both tubes.
The data taken from the lower end of the KOH column were recorded in a table. When the KOH in the control, shifted away from zero, the differences were recorded and adjusted in the data table. For accuracy purposes, the measure in the control tube, that had deviated from zero, was added and deducted, from the data of the Mung bean seeds. The syringe was then adjusted so that KOH was seated at zero, at all times (Daynk, 2012). When the final readings were recorded, the stoppers were removed. The Mung beans seeds were carefully removed as well and weighed on the scale.
All data from the 5-minute interval at 40 minutes total, were recorded. This included both treatments. The means of the data were taken down and plotted into a line graph. The slope of the lines were calculated and presented in figure 1. Results: Figure 1 shows 2 linear lines of best fit, with line y = . 56 being treated with 200 c. Where as, line y = 0. 29 was treated with 100 c. It shows a positive correlation between incubation time and the volume of oxygen consumption. The weight specific respiration for the germinating Mung bean seeds on the 200 c treatment was 116. 8 ml h-1 kg -1. . Where as, with the 100 c treatment, the weight specific respiration was 60. 98 ml h -1 kg -1. Line y = 0. 56 has a steeper slope than line y = 0. 29. A higher temperature treatment of 200 c has higher consumption of oxygen by the Mung bean seeds, as shown in Figure 1. The independent variable in this experiment was the incubation time in minutes. The dependent variable was the volume of oxygen consumed in milliliters. In both treatments, the trend shows that, as incubation time increase, oxygen consumption increase as well.
The temperature treatment of 10 0 c was plotted with symbol-x while the treatment of 20 0 c was plotted with the symbol – Discussions: The experiment has a positive linear graph, on cellular respiration. As incubation time increased, the volume of oxygen consumption increased. The Mung bean seeds that were exposed to higher temperature of 200 c consumed more oxygen, compared to the 100 c. treatment. A higher temperature produces more energy to generate ATP for cellular respiration. Thus created more molecules collision to mediate the enzymes activity in the Mung bean seeds.
This result implied that the hypotheses were true. In order for cellular respiration to happen, oxygen is needed to metabolize the Mung bean seeds, to form ATP. The Mung bean seeds went through Glycolysis, Krebs cycle and electron transport chain to produced ATP. This was proven by the oxygen consumption, carbon dioxide released and the differences in weight for Mung bean seeds, when exposed to two different temperatures. The carbon dioxide was being absorbed by KOH. It was released during cellular respiration as oxygen was being consumed.
The respirometer balanced out the system by the used of KOH and being in a closed system. However, there were some errors that may have caused the results to falsify the hypotheses, especially in the pressure regulation. If the Chinook developed during the experiment, the result of the oxygen consumption will increase, as the surrounding pressure decreases the need of energy increases thus will affect the result. In this case, the control tube used in the experiment helped to regulate the pressure change, like a homeostasis regulation.
If the experiment had half as many seeds, the slope of the line would be less steep and closer to zero. This is due to the demand of energy as being lesser. Therefore, not a lot of oxygen will be needed to complete the cellular respiration. Sometimes the timing of 5-minute interval during the experiment is not so accurate. A stopwatch could be used to eliminate this possible human error. Perhaps a comparison of the experiment with a higher temperature treatment of 300 c and 100 c would give a more significant difference in cellular respiration.
1) Campbell A. Neil, Reece B, Jane, Urry A. Lisa, Cain L. Michael, Wasserman A. Steven, Minorsky V. Peter and Jackson B. Robert. 2008. Biology, 8th ed. Pearson Benjamin Cummings Publishing. San Francisco, California. Pp. 163-177
2) Danyk, Helena. 2012. The Cellular Basis of Life Laboratory Manual. Department of Biological Science. University of Lethbridge, 2012. Pp. 54-56.
3) Frankel, J., et al. Principles of Biology I Laboratory Manual Fifth Edition. Pearson Custom Publishing, Boston. 2005. pp.37-42