Membrane Function Lab Planning – Hour 4, Group 8

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 4, Group 8

  1. Denise G. says:

    Hi! Hopefully I’m in the right place…
    So I think we’re testing for maybe how long the Congo Red dye stays in the yeast cells? Since active transport is needed, the dead/unhealthy cells should keep the color for much longer than the live yeast cells. The dependent can be how long the colors last, although I’m still thinking about independent. Maybe it can be the dead cells or something.

  2. Logan B. says:

    I think that would work for the dependent variable. We could repeat the test to ensure the results. We could also change the amount of yeast or Congo Red we use. I’m not sure if that would change anything though. The independent variable is definitely hard though. I would probably say the amount of Congo Red used.

  3. Jay L. says:

    I think our control group, or standard of comparison, could be a different yeast cell not used in the experiment. This way we can see if the dye looks like it really left the yeast cell. For the dependent variable, the dead yeast cells should not lose their red color at all, so we can just say if the cell loses the red color or not. That change in color could be evidence to confirm it has crossed the membrane. I’m not quite sure about the independent variable, but since all dye should leave the alive cell eventually, I don’t think we should change that. I think that could be a constant, with the microscope and type of dye. Could it be whether the cell was alive or not?

  4. Jay L and Logan B says:

    Our hypothesis was that the yeast cells would actively transport the Congo Red out of the cell, after it was passively transported in. We tested this by comparing alive yeast cells with Congo Red to dead yeast cells with Congo Red. Through this we saw that 90% of the alive east cells became clear, and 90% of dead yeast cells stayed red. This supports our conclusion, as only alive cells can actively transport, so they removed the dye. Both alive and dead cells can passively transport, so both turned red first. Since dead cells cannot actively transport, they stayed red. This shows it is active transport that removed the dye. Some sources of error could be the amount of dye, our observations, and the cleanliness of the slides and microscope.

  5. Denise G. says:

    First, we made 2 slides of live, healthy, unboiled yeast cells, one dyed and the other undyed. The not-dyed one serves asa control group, to make sure change really does happen. We observed them both for a little while, keeping an eye on changes happening on the dyed slide. Next up, we threw away the undyed, healthy yeast slide and replaced it with a dyed unhealthy yeast slide. Keep the 1st dyed and healthy slide. Observe the dead-dyed cell slide, keeping an eye for changes. Jot down your observations and Voila! You’re done.

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