Cell Membranes
Activity #1

What Determines Whether or not a Chemical Compound Can Move Through an Artificial Membrane?

Procedure for Activity #1

1. Prepare two dialysis tubes (made from a colloid) 15 cm long. Twist tightly one end of the tube, fold it over, and tie tightly with string. Prepare both tubes the same way.

2. Take a fresh egg and crack open, allowing the egg white to “flow” into a beaker thereby separating the yellow yolk from the clear egg “white.”

3. Add the egg white to one of the dialysis tubes until it is about 3/4ths full. Twist the open end shut, fold over, and tie tightly with a piece of string.

4. RINSE the outside of the bag and DRY it with a paper towel or equivalent.

5. Prepare a 20% sucrose (table sugar) solution by combining 20 grams sucrose with 80 grams (80 cm³ of distilled water since the density of water is 1.0 g/cm³). Stir to completely dissolve the sugar, then add to the SECOND tube, filling to 3/4ths full. Twist shut the open end, fold over, and tie tightly with a piece of string.

6. Rinse the outside of the bag and dry it with a paper towel or equivalent.

7. Measure the mass of each bag to the nearest 0.1 or 0.01 g, depending on the precision of the balance that you are using.

8. Place each bag in a SEPARATE 250 cm³ beaker with just enough distilled water to completely cover the bag.

9. After 10 minutes, remove each bag, dry with absorbent paper or equivalent and MASS each bag again. Record your data.