How Do Materials Enter Cells???

There are many exercises provided for this lab, far too many to complete during our two hour lab period. Therefore, for this lab, please note the following changes to the lab protocols presented in the lab manual:

Simultaneous Osmosis and Diffusion

• Complete this exercise as presented in the text

Brownian Movement

• We will NOT be performing this experiment

Osmosis

• This will be a classroom demo presented by your TA

Diffusion in Gels

• We will be performing a diffusion in gels exercise, but NOT the one in the text. Please see the revised protocols located at the bottom of this handout.

Diffusion in Gasses

• We will NOT be performing this experiment

Osmosis in Living Cells

• We will be performing this experiment as presented in the lab manual

Osmoregulation in Paramecium

• We will NOT be performing this experiment

Modified Protocol for the Diffusion in Gels Exercise

Diffusion in highly viscous solutions can be demonstrated using agar as a gelling agent. Obtain two petri plates containing 1% agar poured to a depth of 5 mm. Use a drinking straw to make three wells equally spaced in both plates (note: you must remove the agar plug leaving the 5 mm hole in the agar). To one well in each plate, fill the well with methyl blue dye. To a second well in both plates, fill the well with methyl green. Finally to the last well in both plates, fill the well with congo red. CAUTION: THESE DYES PRODUCE PERMANENT STAINS IN CLOTHES! Place one of the plates on your lab bench and carefully place the other plate on ice. Let the agar sit for at least an hour.

After an hour, measure how far each dye has moved in each agar plate. Record these data. You may then dispose of the agar plates in the garbage.

The following data may be of use to answer the questions on the diffusion in gels exercise in the homework:

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