Dialysis Tubing Selective Permeability

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This record below will help in grasp the permeability of dialysis tubing by using a range of solutions. Moreover, it will also show how a variety of solutions diffuse through the selective permeable membrane. Therefore, this experiments are necessary since diffusion is a useful method in the human cells. On the other hand, osmosis is also essential since it is the process that lets in substances in and out of body cells.
Experiment 1: Osmosis
Scientifically, osmosis is described as the diffusion or motion of water molecules through a selective permeable membrane. Notably, water is an important molecule for mobile function and can exist in various concentrations in and out a cell. In this experiment, we will touch on the effect of concentration on the rate of osmosis. Different dialysis tubing is then filled with sucrose solution of different molarities then placed into a cup full of distilled water. In this case, the movement of water through the semipermeable membrane will be shown by the concentration of the solution in the dialysis tubing (Banerjee and Pranab 17). Thereafter, the initial and final masses of these solutions will be noted before and after placed into water. Their percentage change will be computed to show the relationship between the movement of water in and out of the tubing and solute concentration.

Materials and Methods

A solution of sucrose (0.2 – 1.0 molarity)

Dialysis tubing


Distilled Water

Small plastic beakers



Graduated cylinders

Unknown molarity solution

A Cup


Take a strip of dialysis tubing and open it

Pour 10 ml of the designated solution into the tube

Tie both ends of the tube while leaving some space (for expansion of the contents in the bag).

The tubes were dried and weighed and their masses were recorded.

Put the tubes into the flask of distilled water.

Leave them for about 30 minutes.

After that, remove the tubes and dry them again.

Record their new masses.


The table below shows the percentage changes, initial, and final masses of all the solutions of sucrose.


Initial Mass (in g)

Final Mass (in g)

% Change

0.0 M sucrose




0.2 M sucrose




0.4 M sucrose




0.6 M sucrose




0.8 M sucrose




1.0 M sucrose




? M sucrose





The data was plotted on a graph as shown below.

From the graph above, it is evident that as the molarity of the sucrose mixture is directly proportional to the percentage change in the mass. This is so since the water had a tendency to diffuse through the semipermeable membrane (dialysis tubing) into the sucrose solution. The contents of the dialysis tubing became gradually more hypertonic hence allowing more water to diffuse into the bags.

A small space was left in the dialysis bag to allow water to move in and out hence preventing the tube from bursting. Therefore, on applying the corresponding equation and trend line in conjunction with the percentage change of the unknown solution, we can calculate the molarity of the unknown solution as shown below.

Y = 0.251x + 0.003

y = percent change

x = solution molarity


09756 = .251x + .003

x = .3767 M

The table below describes the changes that would have occurred if all the dialysis bags had been put inside in a 4 M solution instead of distilled water.

Treatment in Tube


0.0 M sucrose

Tube is hypotonic, water moves out

0.2 M sucrose

Tube is hypotonic, water moves out

0.4 M sucrose

Tube is isotonic, no net movement

0.6 M sucrose

Tube is hypertonic, water moves in

0.8 M sucrose

Tube is hypertonic, water moves in

1.0 M sucrose

Tube is hypertonic, water moves in


Diffusion is the random movement of molecules which makes them to spread out. This process is extremely important for the function of a cell. Notably, only certain molecules can diffuse across a membrane without any help from proteins. In this experiment, we will concentrate on the elements that promote or inhibit diffusion using dialysis bags, Iodine solution, glucose and starch solution to identify which particles or molecules will diffuse through the permeable membrane which is the dialysis bag in this case (Nix, Staci and Staci 165).


The glucose will diffuse through the dialysis tubing while the starch won’t due to its large complex three D shape.

Materials and Methods

Iodine solution

Distilled water

Dialysis tubing


Solution of soluble starch and 15% glucose

Small beaker

Glucose test tape stripes

Graduated cylinders


Benedicts solution.


Take a strip of dialysis tubing and cut a piece of about 6 inches off.

Dip the tubing in water to make it easier to open.

Tie one end of the tubing then fill it with 30 ml of soluble starch and glucose solution.

Tie the other end of the tubing with a string.

Before pouring the glucose solution into the dialysis tube, a glucose test tape strip was used to confirm that there was glucose in the solution by putting the strip into the solution and waiting a few minutes.

The strip turned a dark shade of brown to indicate the presence of glucose.

In a cup filled with water, and then 20 ml of iodine solution was added to the water which turned the water a gold color.



To begin, after the dialysis tubing was put in water for a few minutes, I saw the solution inside the tubing turned blue in color. This showed that the iodine solution had moved through the permeable membrane into the extracellular fluid hence an indicator that the tubing was permeable to iodine. Moreover, the water remained a gold color. This indicated that the starch present in the solution did not move out of the dialysis tubing. In other words, this showed that the pores in the membrane were not large enough to allow diffusion of starch.

I then used another different glucose strip to determine if any glucose had moved into the water. In this case, the glucose strip turned brown for the second time hence showing that the membrane pores were big enough to allow movement of glucose molecules and that the glucose did diffuse into the water. Based on the above results, I would rank the following items in order from tiniest to the largest as shown:




Membrane pores


Besides, if the experiment was repeated with another substance like sucrose, the outcome would most likely not change. Notably, sucrose is a disaccharide which is composed of monosaccharide glucose and fructose. Despite the result, some possible sources of error include the string tied to the tubing being too loose and allowing molecules to flow through the open tube instead of the membrane. Moreover, the tubing might not have been submerged in the water long enough for the diffusion to reach equilibrium.

Works Cited

Helms, Carl W. Biology in the Laborary: Osmosis and Diffusion. Place of publication not identified: W H Freeman, 1997. Print.

Banerjee, Pranab K. Introduction to Biophysics. Place of publication not identified: S Chand & Co Ltd, 2010. Print.

Nix, Staci, and Staci Nix. Williams’ Basic Nutrition and Diet Therapy. St. Louis, Mo: Elsevier, 2013. Print.

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