Home ยป Biology Lab: Cellular Respiration Notes

Biology Lab: Cellular Respiration Notes

Cellular Respiration Introduction

Lab Objective: In this lab, we are testing how the process of cellular respiration is affected by temperature, and also how it is different between germinating and non-germinating peas. Cellular respiration is a catabolic process (breaks down organic material into usable cell energy) that produces ATP. The electron receivers are inorganic. Cellular respiration releases energy from organic material through chemical oxidation within the mitochondria of cells.

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Cellular respiration usually refers to the metabolizing of glucose, however carbohydrates, proteins and fats can also be metabolized. C6H12O6 + 6O2 > 6CO2 + 6H2O + 686 Kcal of energy/mole of glucose oxidized Cellular respiration can be measured by looking at the consumption of O2, the production of CO2, and the release of energy. PV=nRT is known as the inert gas law where: P is the pressure of the gas, V is the volume of the gas, n is the number of molecules of gas, R is the gas constant, and T is the temperature of the gas in degrees Kelvins.

This law is very important and we can infer many things when given some parts of the equation, for example: “if the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume”, that is just one of the direct proportions. Also in this lab, potassium hydroxide (KOH) can be used to remove the CO2 produced during cellular respiration, therefore the change in volume in gas we see in our respirometer will be directly related to the amount of oxygen consumed by the peas. The reaction is: CO2 + 2KOH > K2CO3 + H2O Materials: 0 germinating peas, 20 dry peas, 225 glass beads (approx. ), 6 mL 15% potassium hydroxide, 2 water baths, 6 respirometers, 6 absorbent cotton balls, 6 nonabsorbent cotton balls, 50-100 mL graduated cylinder, thermometer, pipet, stopwatch, ice, food coloring, paper towels Methods: The first thing we did for this lab was set up 2 water bath/trays, one with water at room temperature and the other we kept at a constant 10 degrees Celsius by adding ice into the tray. We were also provided with 6 vials with steel washers, in which we labeled them 1-6.

We then filled a graduated cylinder to 13 mL water ( we kept it constant throughout the lab . ) First we added 10 germinating peas into the graduated cylinder and then took a reading of the displaced water. We recorded this data, decanted the water, and placed the peas to dry on a paper towel. We repeated this process, but instead we added 10 non-germinating peas also with glass beads until the water level was the same as the germinating peas, and then placed them to dry on a paper towel. Next we repeated the process, but we added only glass beads until the water level was same as the germinating peas.

We repeated the same steps respectively and set the second set of peas and beads aside for use in vials 4-6. For the next part of the lab we placed an absorbent cotton ball into each of the 6 vials and pushed each to the bottom of the vials. We then carefully added 1 mL of provided 15% potassium hydroxide (using pipets) to each of the cotton balls, after that we placed a piece of non-absorbent rayon on top of the KOH soaked cotton. With the first set of germinating peas, non-germinating peas, and glass beads we added them into vials 1-3 respectively.

We added the second set of peas and glass beads into vials 4-6. We had graduated pipets with stoppers at the end provided. We then placed each stopper into each of the vials, creating a seal; and we then placed a washer over the pipet on top of the stopper (so that the vials are weighed down in the water baths later. ) After that we placed vials 1-3 into the room temperature water bath, with the pipet ends resting on the edge of the water tray, and placed vials 4-6 into the chilled water bath and allowed the vials (respirometers) to equilibrate for 10 minutes.

After that we put one drop of food coloring into the exposed tip of each respirometer and waited 1 minute, and proceeded to turn each respirometer so that the graduation marks face up and fully submerge each respirometer into their baths and waited another 5 minutes. Now we began to read the respirometers (how much the dye moved) to the nearest 0. 01 mL and took the temperatures of each water bath. We took additional readings every 5 minutes for 30 minutes and recorded the readings and temperature in the data table provided.

We then calculated the differences and corrected differences using the following formulas. We were only able to get 3 readings at a total of 10 minutes. Difference = (initial reading at time 0) – (reading at time X) Corrected difference = (initial pea reading at time – pea sea reading at time X) – (initial bead reading at time 0 – bead reading at time X) Results: |Germinating Peas |Dry Peas & Beads |Beads only | Vials 1-3 TEMP (Celsius) |Time (Min) |Reading |Diff. |Corr. Diff. |Reading |Diff. |Corr.

Diff |Reading |Diff. | |18 |0 |. 80 |- |- |1. 10 |- |- |. 65 |0 | |18 |5 |1. 45 |-. 65 |-. 65 |1. 10 |0 |. 05 |. 70 |-. 05 | |18 |10 |1. 75 |-. 95 |-. 90 |1. 10 |0 |. 05 |. 70 |-. 05 | | |15 | | | | | | | | | | |20 | | | | | | | | | | |25 | | | | | | | | | | |30 | | | | | | | | | |Vials 4-6 8 |0 |1. 65 |- |- |1. 05 |- |- |. 90 |- | |9 |5 |1. 65 |0 |. 1 |. 8 |. 25 |. 35 |1 |-. 10 | |9 |10 |1. 25 |. 4 |. 4 |. 5 |. 55 |. 55 |. 90 |0 | | |15 | | | | | | | | | | |20 | | | | | | | | | | |25 | | | | | | | | | | |30 | | | | | | | | | | | | | | | | | | | | |[pic] Data analysis:

In this lab the vials with beads only serve as a control, because the beads do not go through cellular respiration. With the data from vials 1-3 we can see that the dye travelled the most in the respirometer with germinating peas, this is because in cellular respiration germinating peas require the most oxygen to survive and grow. The dye is travelling because as the oxygen is being consumed by the peas, the oxygen is being taken out and the pressure within the respirometer decreases; pulling the dye towards the respirometer.

While non-germinating peas are also alive, they currently require much less oxygen to survive. In vials 4-6 from what I see looking at the non-germinating peas, the readings are smaller, meaning in a cold temperature setting cellular respiration is less efficient. The data from the germinating peas in the chilled water bath do not show this, however I think an error was made. Conclusion: From this lab I am concluding that a higher temperature means higher efficiency for cellular respiration.

We can also see the differences in cellular respiration between germinating and non-germinating peas. In our lab the main error made was that I accidentally bumped the chilled water tray, moving the respirometers equilibrating inside the tray, therefore resulting in botched results. CELLULAR RESPIRATION ASSESSMENT QUESTIONS 1. The rate of oxygen consumed by germinating peas increases over time (at least in 1 of out data sets), meaning that they require a lot of oxygen to survive. . Three controls used in this lab are the temperatures of the water baths, the amount of KOH added to the vials, and the time intervals in which we recorded rates of oxygen consumption. 3. The water initially moved into the respirometer because we had to fully submerge the respirometer. I don’t think we could have avoided some water getting inside the graduated pipet. 4. The role of KOH is to prevent the release of CO2, but K2CO3 we see at the bottom of the respirometers.

Without CO2, we can accurately measure how much oxygen is being used without the release of CO2 effecting those readings. 5. The KOH absorbs the CO2, therefore affecting the volumes within the respirometer. 6. Germinating peas consume more oxygen than non-germinating because they have a higher metabolic rate and need more oxygen in order to survive and grow. 7. The lower the temperature, the less efficient respiration was. 8. In aerobic respiration, the carbon atoms go into the CO2, the oxygen and hydrogen go into the H2O and the energy is turned into ATP. 9.

Fermentation is a catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and produces an end-product like ethyl alcohol or lactic acid. The two types of fermentation are alcoholic and lactic acid fermentation. Plants use alcoholic while animals use lactic acid. 10. 11. The breakdown of glucose involves glycosis, the Krebs cycle, and electron transport system. Glycosis occurs in the cytoplasm while the Krebs cycle and electron transport system occur in the mitochondria. 12. 1. b 2. c 3. a 4. c 5. c 6. c 7. a 8. b 13.


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