The purpose of this experiment was to study the effects of ethanol on the cellular respiration of mealworms. Cellular respiration is the process by which cells harvest the energy stored in food. It is the intake of oxygen and energy in the form of glucose, and the cells ability to break it down into carbon dioxide, water, and energy required for the body to function. More scientifically, it is a three-step pathway that produces ATP (adenosine triphosphate.) The three stages of cellular respiration are: glycolysis, the citric acid cycle, and electron transport.
Ethanol is a volatile, colorless liquid and is considered a psychoactive drug. Ethanol is generally known to have depressant effects on the central nervous system. If you subject mealworms to a 95% ethanol solution, then the rate of cellular respiration will decrease.
Materials and Methods
The materials used in this experiment were: 12 beetle larvae (mealworms), 1 – 250 ml Erlenmeyer flask, a ring stand and clasp, a Data logger, an AC power adapter for the data logger, forceps, filter paper, 95% ethanol solution and a dropper. The experiment began by adding 12 live mealworms to the flask. The data logger was then calibrated and used to take an initial CO2 output reading. Readings were again taken every minute for a total of 15 minutes. These readings were recorded and used as the control. Next, the dropper was used to add 7 drops of the 95% ethanol solution to the filter paper. The filter paper was inserted into the flask with the mealworms. The data logger was again used to take CO2 output readings at one-minute intervals for 15 minutes.
Results
This experiment showed the effects of ethanol on the cellular respiration of mealworms. Respiration rates were recorded in both the control group (no ethanol) and the experimental group (ethanol.) The initial readings in the two groups were very different, with the control group starting out with a much higher rate than the experimental group. Both groups showed progressively increased rates as time elapsed.
Overall, the CO2 output in the control group, with no ethanol, increased by 690 ppm over the 15 minutes, producing an 81.18% change. The experimental group, with the 95% ethanol solution, increased by 857 ppm, producing a 125.11% change.
RATE OF CELLULAR RESPIRATION IN BEETLE LARVAE WITH/WITHOUT ETHANOL | Time Intervals Minutes | Control Treatment No Ethanol | Experimental Treatment 95% Ethanol | | | | 0 | 850 | 685 | 1 | 915 | 760 | 2 | 971 | 844 | 3 | 1031 | 920 | 4 | 1083 | 982 | 5 | 1128 | 1046 | 6 | 1177 | 1108 | 7 | 1222 | 1169 | 8 | 1266 | 1212 | 9 | 1307 | 1267 | 10 | 1349 | 1311 | 11 | 1397 | 1367 | 12 | 1436 | 1414 | 13 | 1475 | 1462 | 14 | 1513 | 1503 | 15 | 1540 | 1542 | Change in CO2 (ppm) | 690 ppm | 857 ppm | Percent Change in CO2 (%) | 81.18% | 125.11% |
Discussion
Our hypothesis stated that, if we subjected the mealworms to the ethanol, then the rate of cellular respiration would decrease. Our experiment did not support our hypothesis. In fact, the opposite was documented. The control group, with no ethanol, produced an 81.18% increase in CO2 production over the elapsed 15 minute time period. However, the experimental group, with the 95% ethanol, produced an increase of 125.11% CO2 production over the same elapsed time. Why would ethanol, a depressant, produce an increase in cellular respiration?
One possible explanation is that our initial readings in each group were not consistent with each other. The control group initial reading was 850 ppm; whereas, the experimental ethanol group started out much lower at 685 ppm. These initial readings do support our hypothesis that cellular respiration was decreased in the mealworms subjected to the ethanol solution. It is only with the elapsed time that the ethanol treated mealworms had increased respiration rates. It was also interesting to note that after 15 elapsed minutes, both groups ended up with nearly identical total CO2 output. The control group ended with 1540 ppm and the ethanol treated group with 1542 ppm.
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