Membrane Function Lab Planning – Hour 1, Group 5

Consider the following questions to help you get started:

  • What variable will you be testing (independent variable)?
  • What variable(s) will you be measuring (dependent variable)?
  • What variables will you hold constant (constant variable)?
  • What evidence would confirm that the stain has crossed the membrane?
  • How will you be confident in the validity of your results?
  • What will you use as a standard of comparison (control group)?

Use the comment form below to discuss the plan for your experiment.

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5 Responses to Membrane Function Lab Planning – Hour 1, Group 5

  1. Josh S says:

    Hi guys I have an activity to do the rest of the night, so i am going to do my ideas now. I thought the independent variable would whether the yeast was alive or not. Then the dependent variable would be the color changes based on the dye. I thought some of the constants could be the microscope, sunlight,and amount of Congo red. I did not have a great idea about the control. One idea is to just do both of them twice. For the living ones we could put the Congo red back in the yeast after they turned white again. This would show that the cells were indeed still living. We could prove that the stain did cross the membrane by seeing the red in the inside of the cell, and not just on the outside. If you guys have something you want to change we can talk about it at school, but I have to go.

  2. Lauryn V says:

    First, we can conduct an experiment using the boiled yeast cells to observe what passive transport looks like. We know that the dead cells can’t push out Congo red, so the dye should stay in the cells and turn them red. After about a minute of allowing passive transport to take place, we can record our final results and move on to the second experiment. For the second experiment, we can do the same procedure with living yeast cells instead of dead yeast cells. After about a minute of allowing the Congo red molecules to be transported, we can view the molecules. If we get the same results in the dead and living yeast cells, active transport did not take place because the Congo red did not leave the cell. If we get different results and the living yeast cells appear somewhat clear, active transport did take place and allowed the cell to push out the Congo red.

  3. Carter Smith says:

    Lauryn that’s a good idea. For the control we can make sure to use the same amount of die in each experiment. It is a good idea though to do each experiment twice to prove that it is valid. If the die gets pumped out of the active cells twice and stays in the dead cells twice than we know that the experiment is successful.

  4. Lauryn V and Carter S says:

    Summary:
    First, we gathered our supplies and put the living and dead yeast cells on separate slides. Then, we added the Congo red to the slides and removed the access dye. After letting the solution sit for two minutes, we used the microscopes to observe the cells. We noticed that all of the dead yeast cells were bright red. At first, some of the living yeast cells were red, but after time, the all turned a clear, “normal” color. This proved that the living cells active transported all of the Congo Red out of the yeast cell. Therefore our hypothesis was correct. Passive transport moved the Congo red into the cells and active transport moved it out.

  5. Josh S says:

    Conclusion
    The Congo red moved into both the living and boiled yeast cells through passive transport (diffusion) and exited the living yeast cells through active transport. The boiled cell remained red because they did not have the energy to accomplish active transport. The evidence of this is that both the living and dead cells had the Congo red diffused into them when we inserted the Congo red into their cells. The inside and outside of the majority of the cells had turned red. This can be proved to be passive transport because the boiled or unhealthy cells could do this because diffusion does not require any energy from the cell. Then, after several minutes of waiting, the living cells and actively transported the Congo red out of their cells. The majority of the cells had turned back to the same color they were before we had inserted the Congo red. Several of the cells remained red because perhaps a few of them were not actually living. The dead cells still had the majority of them being red. A few of them could have changed because they might have been living, or they had never absorbed any Congo red in the first place. This proved that the Congo red had exited through active transport, because only the living cells were able to have the energy to do this. If they had left through passive transport, it would have exited though both types of cells, but it required energy to leave, so only the living cells did this. Some possible sources of error are the amount of Congo red, the Congo red did not stain all of the cells, the amount of water, amount of cells, and the fact that some of the living cells could have been dead or the dead cells were alive.

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