Modelling the digestive system

This is a common experiment used to model the digestive system and will help you understand how to work scientifically.

To use Visking tubing to model the digestive system and show what substances can pass through its lining.

1. Set up two sets of the apparatus as in the diagram.

2. Put 1cm³ of amylase enzyme into tube 1 but not tube 2.

3. Leave at room temperature for five minutes.

4. Test for starch (using iodine) and glucose (using Benedict’s reagent) inside and outside both tubes.

• Independent variable: the presence or absence of amylase.

• Dependent variable: the presence or absence of glucose inside and outside the tubing.

• Controlled variables: the quantities of the solutions used, the time taken before testing and the temperature of the water.

Find out more about variables

1. There is no starch outside the Visking tubing. It is too large to pass through the tubing.

2. Glucose is present in the solution containing amylase (tube 1), but not in the solution that doesn't contain amylase (tube 2). Amylase breaks down starch into glucose.

3. There is glucose outside the Visking tubing in tube 1 as glucose is small enough to pass through the tubing.

At the end of an investigation, it is important to evaluate the results and the method. After this is done, a judgement is made about how reliable the conclusion is.

Find out more about evaluating results

Use Benedict's reagent in another experiment in Atomic Labs. Go to the Biology lab and try the Testing for sugar experiment.