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Aerobic Metabolism: Evolution of a New Energy-Producing Pathway

Digital Lab Report #9

By: Hadi Makkawi, Ziad Toqan, and Aziz Al-Harbi

Purpose…

  Three Key Purposes of the Lab:   1. To be able to list the parts of the mitochondrion and describe

its activities in aerobic respiration

  2. Discuss the mitochondrion as a product of endosymbiosis.

  3. Summarize the products and by-products of aerobic metabolism.

Procedure A: Oxygen Consumption

  1. First we filled a test tube with 10 germinating peas and placed a loosely-packed cotton plug above the peas with some air space in between. On top of the cotton plug we inserted 10 pellets of potassium hydroxide (KOH).

  2. Then, we inserted a respirometer with a drop of indicator fluid in place. We then waited approximately 5 minutes before taking any readings to make sure all was accurate.

  3. Third, we placed 10 dry peas in another test tube and inserted the respirometer the same way as before.

  4. We recorded the position of the fluid droplet in both respirometers every three minutes for half an hour.

Procedure B: Carbon Dioxide Production

  1. For the second part of the procedure we repeated the steps in procedure one except this time we left out the KOH.

  2. We then noted the position of the fluid droplet in both respirometers every three minutes for half an hour.

Table Measuring: Oxygen Consumption and Carbon Dioxide Production in Aerobic

Respiration

Time Tube 1. Germinating peas

Tube 2. Dry Peas

Tube 3 Tube 4

0 12.7 10.0 7.7 0

3 12.4 9.4 7.4 0.2

6 12.1 9.0 7.3 0.3

9 12.0 9.0 7.2 0.5

12 11.7 8.9 7.1 0.6

15 11.5 8.8 7.0 0.6

18 11.5 8.8 6.9 0.6

21 11.5 8.8 6.9 0.6

24 11.3 8.8 11.5 0.6

27 11.1 8.9 12.2 0.6

30 11.0 8.9 12.5 0.6

Part A: Oxygen Consumption Part B: Co2 Production

Analysis of Recorded Data…

  Analysis of recorded data:   As we can observe from the data recorded, KOH does indeed absorb

carbon dioxide. Through this experiment, we were able to see that when KOH was added to the test tube filled with germinating peas the level of oxygen consumption decreased before reaching a stabilizing. In the case of dry peas, when the KOH was present the oxygen consumption of the peas also saw a decline until reaching a stable level.

  For part B, the test tube with germinating peas excluding KOH saw an increase in carbon dioxide production until the middle until it slightly dipped. This however was a mistake on our part as we tampered with the respirometer. The intended outcome should have showed continued increase in CO2 production. As for the tube filed with the dry peas excluding the presence of KOH, CO2 production increased slightly until finally reaching a stable level of 0.6.

Graphed Data from Table Observations

General Analysis

  The table and graph presented inthe earlier slides display the oxygen consumption and carbon dioxide production in two different situations. The first is of KOH in the presence of germinating peas and dry peas, and the second without any addition of KOH to tubes of germinating peas and dry peas. The experiment more or less shows that the carbon dioxide production was somewhat approximately equal to that of the oxygen consumption in aerobic respiration. Since KOH is highly basic, it forms strong alkali solutions in water and other polar solvents. This information presented through the data comes to verify the initial hypothesis that KOH absorbs carbon dioxide, and that is why when the KOH was removed from the setup, we saw carbon dioxide production levels increase. And when KOH was present in the germinating peas solution, we saw a decrease in the oxygen consumption levels.

Conclusion...

  This lab contributes to one of the key goals of the course as it informs its lab conductors of the very idea that the evolution of metabolic pathways such as aerobic respiration, and their merging into major lineages of organisms, may have permitted life as we know it to survive through evolutionary time. This can be seen as significant as the evolution of aerobic metabolism, which is considered a metabolic pathway that allows large amounts of ATP to be produced with the presence of oxygen, as a crucial event in the history of evolution. It is what was needed in order for multi-cellular organisms to evolve and develop, which need higher amounts of energy than unicellular anaerobic bacteria.