Isra Romani
Lab Report 2: Diffusion and osmosis through non-living membranes
Introduction
Cells contain membranes that are selectively permeable which allow certain things to pass into
and leave out of the cell. The process in which molecules of a substance move from an area of
high concentration to areas of low concentration is called diffusion. Whereas Osmosis is the
process in which water crosses membranes from regions of high water concentration to areas
with low water concentration. While molecules in diffusion move down a concentration
gradient, molecules during osmosis both move down a concentration. During the osmosis both
move down a concentration as well as a cross it. Diffusion and osmosis are type of passive
transport
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PURPOSE
To provide information on the movement of water and solutes through selectively
permable membranes called dialysis sacs.
Materials
4 dialysis sacs ( have pores on a particular size)
Small funnel
25-ml graduated cylinder
Wax marking pencil
Fine twine or dialysis tubing clamps
4-250ml beakers
Laboratory balance
Glucose solution
Nacl solution
Congo red dye in 40%sucrose solution
Paper towel
Procedure
1. Number the beakers 1 to 4 with the wax marking pencil, and half fill all of them with the
distilled water except beaker 2, to which you should add 125ml of 40%glucose solution.
2. Prepare the dialysis sacs one at a time by using the funnel, half fill each with 20ml of the
specified liquid.
3. Press out the air, fold over the open end of sac, and tie it securely with fine twine or
clamp it before proceeding to the next sac. Rinse it under the tap, and quickly and
carefully blot the sac dry by rolling it on a paper towel.
4. Weigh with a laboratory balance. Record the weight and drop the sac into the
corresponding beaker. Make sure the sac is covered by beaker solution.
Contents of sacs
Sac 1: 40% glucose