Dictyostelium and diffusion

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Pre-Lab:

1. Define hypotonic, isotonic, and hypertonic.

2. Predict what will happens to cells when placed in each of the three environments.

Exercise 1: Osmotic Environments on Cell structure

In this experiment you will be testing three different osmotic environments on cell structure and life using the cellular model Dictyostelium discoideum: hypertonic, hypotonic, isotonic.

Place 300 uL of cell culture onto a clean coverslip and allow 10 minutes for cells to adhere.
Gently tilt the slide at an angle and remove the excess media
Add 300 uL of either hypotonic (sterile H2O), isotonic (HL5 media), or hypertonic (0.1M sucrose water)
Allow coverslip to sit for an additional 10 minutes.
Gently tilt the slide at an angle and remove excess fluid
Place the coverslip upside down onto a clean slide for viewing.
View cells under microscope at 40x and record observations for time 10 minutes in the table below. Photograph representative cells for each time point. If cells differ in appearance, record the number with each appearance.
Repeat observations and imaging after 5 and 10 minutes. Record in the table.
Repeat with other two osmotic environments.

Record Observations in this table:

hypotonic

isotonic

hypertonic

10 minutes

15 minutes

20 minutes

Post-Lab Report

1. Create a figure showing the change in cells (if any) in the three conditions.

2. Write a paragraph describing the results of your experiment, including control results. Include answers to the following questions:

Were the changes you observed consistent with your predictions? Why or why not?
Did the timing of any changes differ among the samples (did some treatments cause faster or slower response)? Was this expected, why or why not?