visking tube experiment starch and amylase

Practical Biology

A collection of experiments that demonstrate biological concepts and processes.

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Published experiments

Investigating the effect of amylase on a starchy foodstuff, class practical or demonstration.

Place rice in a Visking tubing bag to model food in the gut . Investigate amylase action by adding water, amylase, or boiled amylase to the rice. Leave for 10-15 minutes in a water bath at around 37 °C then test for the presence of a reducing sugar in the water surrounding the Visking tubing bag.

Lesson organisation

This experiment could be done as a demonstration or in groups. Each group needs to set up three Visking tubing bags, so a group of 3 students is ideal.

Apparatus and Chemicals

For each group of students:.

3 x 15 cm lengths of Visking tubing

Syringe barrels, sawn off, 3

Boiling tube, 3

Test tubes, 6

Test tube racks to accommodate 6 test tubes and 3 boiling tubes per group

Teat pipettes, 6

White dimple (spotting) tile

Beaker, 250 cm 3

Kettle for boiling water for Benedict’s test

Eye protection for each student

For the class – set up by technician/ teacher:

Length of Visking tubing, knotted at one end, 15 cm, 3 per group ( Note 1 )

Syringe barrel, sawn off, 3 per group ( Note 2 )

Elastic bands, 3 per group

Electric water baths set at 35-40 °C, with thermometer to show temperature accurately

Cooked rice

Iodine solution ( Note 3 )

Benedict’s reagent ( Note 4 )

Amylase solution, 5 cm 3 per group ( Notes 5 and 6 )

Boiled amylase, 5 cm 3 per group

Clinistix (as an alternative to Benedict’s reagent) ( Note 7 )

Health & Safety and Technical notes

Students should wear eye protection when handling chemicals. Electrical apparatus should be maintained and checked according to your employer’s instructions. Ensure students know how to deal with breakages of glass or thermometers

Read our standard health & safety guidance

1 Soak the Visking tubing in warm water beforehand so it is ready to use.

2 The end of an old syringe makes a convenient support for the Visking tubing, and makes it easier to take samples of the contents with a teat pipette.

3 Iodine solution (See CLEAPSS Hazcard and Recipe card): a 0.01 M solution is suitable for starch testing. Make this by 10-fold dilution of 0.1 M solution. Once made, the solution is a low hazard but may stain skin or clothing if spilled.

4 Benedict’s (qualitative) reagent. (See CLEAPSS Recipe card) No hazard warning is required on the bottle, as the concentrations of each of the constituents are low. Take care making up the reagent; sodium carbonate is an irritant to the eyes and copper(II) sulfate(VI) is harmful if swallowed. See CLEAPSS Hazcards.

5 Amylase solution: Check your amylase supply as many contain starch or reducing sugars, which would interfere with the results of this test. Alpha amylase is bacterial amylase with high activity, and does not give a positive reducing sugar test or starch test. You can use lower concentrations of this enzyme. Some bacterial amylases may survive boiling!

Using saliva: the CLEAPSS Laboratory Handbook provides guidance on precautions, including hygiene precautions, for safe use of saliva as a source of amylase. This has the advantage of being cheaper and technicians do not need to make up fresh solutions each lesson. It is directly interesting to students, and salivary amylase is reliable. It also provides an opportunity to teach good hygiene precautions, including ensuring that students use only their own saliva samples.  Provide small beakers to spit into. Students must be responsible for rinsing their own equipment. All contaminated glassware is placed in a bowl or bucket of sodium chlorate(I) for technicians wash up.

6 Working with enzymes: It is wise to test, well in advance, the activity of stored enzymes at their usual working concentrations to check that substrates are broken down at an appropriate rate. Enzymes may degrade in storage, and this allows time to adjust concentrations or to obtain fresh stocks.

7 Clinistix are quick and easy to use. Each stick can be cut into two or three pieces.

Ethical issues

There are no ethical issues associated with this protocol.

Preparation

a Prepare boiled rice, enzyme solution, boiled enzyme solution, iodine solution, and Benedict’s reagent.

b Set up a water bath at 37 °C.

c Soak Visking tubing, cut 15 cm lengths (3 per group) and set up model guts with syringe barrels, or leave for students to assemble.

Investigation

d Label 3 boiling tubes 1, 2, 3.

e Label 3 test tubes 1, 2, 3.

f Set up 3 model guts: take a wet piece of Visking tubing, tie a knot in one end, place the sawn off syringe barrel in the other end and secure with an elastic band. These may have been set up for you (see diagram).

g Use the spatula to add rice to each of the model guts until they are half full.

h Rinse the outside of each piece of Visking tubing under a running tap.

i Place the rice-filled model gut in a labelled boiling tube. Add warm water to boiling tube outside the Visking tubing until it reaches about 2 cm higher than the level of the liquid inside the Visking tubing (see diagram).

j Immediately withdraw one drop of the water you have added and test it with iodine on a dimple tile.

k Add 5 cm 3 of water to model gut 1.

l Add 5 cm 3 of amylase to model gut 2.

m Add 5 cm 3 of boiled amylase to model gut 3.

n Place all the boiling tubes containing the model guts in the water bath at approximately 37 °C.

o Leave for at least 15 minutes.

p While you are waiting:

• Place a grain of rice in a well on the white tile and add a drop of iodine.
• Put some rice in a test tube. Add 2 cm 3 of water and 2 cm 3 of Benedict’s reagent, and place into a large beaker of boiling water. Check the colour after 2-3 minutes.
• Record your results in a suitable table.

q After 15 minutes, use a teat pipette to remove 2-3 cm 3 of the water surrounding the model gut in boiling tube 1.

r Place one drop of this water in a well on the white tile and add a drop of iodine. Record the result.

s Place the rest (around 2 cm 3 ) of the water from boiling tube 1 into test tube 1. Add an equal volume of Benedict’s reagent and place test tube 1 into a large beaker of boiling water. Check the colour after 2-3 minutes. Record the result.

t Repeat steps q , r , s with water from boiling tubes 2 and 3. Record the results.

Teaching notes

The sawn off syringe barrel acts as a model mouth to the gut. It is a good idea to use cooked rice, as this is real food and can be seen in the (model) gut.

Many students will need help to understand this activity. When interpreting the results, students have to think in terms of two types of model: the model gut with Visking tubing representing the selectively permeable membranes lining the gut wall, and a simplified chemical model of large and small molecules. A further complication is that the movement of chemicals is unseen and only inferred from the results of chemical tests. An additional model could be used, with chicken wire or mesh, fruit or satsuma bags to represent the membrane, and poppet beads in chains to represent starch and singly to represent glucose.

Health and safety checked, September 2008

Related experiments

Evaluating Visking tubing as a model for a gut

Investigating the effect of pH on amylase activity

Digestion of starch by microbes

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Visking Tubing

This resource describes a visual way of demonstrating diffusion through a semi-permeable membrane. It can be used as a model for the human gut or for investigating the effect of amylase on starch. Two standard tests are used. The first uses iodine to test for starch and the second test uses Benedict’s reagent to test for the presence of reducing sugars, such as glucose.

This resource was produced following National Science & Engineering Week 2013, during which teachers and technicians nominated their favourite demonstrations to be turned into video resources with accompanying written guides.

This resource was funded by the Gatsby Charitable Foundation.

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Please be aware that resources have been published on the website in the form that they were originally supplied. This means that procedures reflect general practice and standards applicable at the time resources were produced and cannot be assumed to be acceptable today. Website users are fully responsible for ensuring that any activity, including practical work, which they carry out is in accordance with current regulations related to health and safety and that an appropriate risk assessment has been carried out.

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ScienceDemo.org

Modelling digestion using visking tubing

This is the second Biology film we’ve made as part of the “ Get, Set, Demonstrate ” project. One of the films we were asked to look at was “Making Poo: The Digestive System” but we felt that this was not what we would strictly call a “demonstration” of digestion (since no actual digestion takes place), but rather an illustration of the process. Instead, we chose to make a film about using Visking tubing to model digestion and use it to explore the reasons why you might choose to carry out a demonstration of an activity which can be (and often is) done as a class practical.

3 thoughts on “Modelling digestion using visking tubing”

Visking tubing is an excellent model for a partially permeable membrane. Great for osmosis demonstrations too, measuring the mass of the tube before and after placing it in concentrations of salt water.

Rather than a solution of starch and glucose, I use a sample of saliva (just chew a disinfected elastic band) to add to the starch to show how it is broken down by the enzyme to produce smaller sugars. Maltose is small enough to get through the visking tubing and is a reducing sugar so reacts with the Benedict’s test.

What are the advantages and disadvantages of doing the Visking Tubing experiment?

what does the water represent

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Theatre, props and explanations, oh my!

3.3.5 Visking Tubing Practical: Biology AQA A level Revision

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Visking tubing gut model is doing my head in..

• Thread starter Wervelwind
• Start date Jun 8, 2022
• Jun 8, 2022

Hi guys. For the visking tubing practical with amylase and starch, how long do you leave it in the water before doing the Benedict's test on the water? Not getting any glucose positives at all...  

From experience, this experiment can be iffy. Have you trialed first that the amylase is breaking down the starch? I have known teachers to doctor the results with a sleight of hand dropping pipette full of glucose solution in the past. Shhhh....  

Snailo said: From experience, this experiment can be iffy. Have you trialed first that the amylase is breaking down the starch? I have known teachers to doctor the results with a sleight of hand dropping pipette full of glucose solution in the past. Shhhh.... Click to expand...

Wervelwind said: Yeah the amylase works fine and the inside of the tubing is a strong positive for sugar. The water itself turns the smallest bit bluegreen but this takes like 30 minutes. A very, very slight change. I was thinking that using less water, or more starch would help Click to expand...

Thanks for all the responses. I think leaving it overnight may be the best thing  

Wervelwind said: Thanks for all the responses. I think leaving it overnight may be the best thing Click to expand...

Paul said: and add some glucose to the outside water when no one is looking Click to expand...

It's real Science not Rocket Science

We've never got it to work so went for fudging it - apparently the gel that the stuff is made with blocks the pores and has to be washed for several hours in hot running water (not feasible). Try to get some that has a high Dalton number (a measurement of the size of molecule that will pass through the pores)  

Finally got a positive result (it turned greenish but I'm content with it). However, it took 90 minutes and a long stuffed visking tube jammed inside a boiling tube filled with just enough water to cover it. I'm calling it a day as my ego is pleased  

Lesley Newcombe

St Caths Crew

• Jun 9, 2022

St Caths Crew said: I am shocked by the number of people who are doctoring their results We always add a bit to ensure results, can take ages to work otherwise. Click to expand...

I always thought you doctored the starch with glucose, rather than the water, but both work!  

CgPD said: I always thought you doctored the starch with glucose, rather than the water, but both work! Click to expand...

• Jun 10, 2022

Lesley Newcombe said: The pupils may want to test the starch for glucose too, I have had lessons where they have decided to do that! Click to expand...

Evaluating Visking tubing as a model for a gut

labsleuth said: We did it this way recently and it worked well. Obviously this method doesn't have the amylase present, but you could add some anyway so the results look like they've come from the break down of the starch instead of just the glucose passing through. Then test inside and outside for starch and outside for sugar? Evaluating Visking tubing as a model for a gut Practical Biology practicalbiology.org Click to expand...

Wervelwind said: Did the water turn red for you after 15 minutes? Click to expand...

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Digestion & Absorption ( AQA A Level Biology )

Topic questions.

Define the biological term, ‘absorption’.

How did you do?

The liver and stomach are both major organs of the digestive system. State why the stomach is classified as part of the alimentary canal whereas the liver is not. 

Use your knowledge of digestion to complete the boxes labelled K , L and M in Table 1 . The first row has been completed for you as an example. 

The salivary glands and the pancreas both act as glands in the process of digestion. State what is meant by the term, ‘gland’ in the context of digestion. 

Did this page help you?

Outline two physical changes that occur to food in the mouth as food is being prepared for swallowing and further digestion. 

Name three conditions of the gastric (stomach) environment that enable chemical and physical digestion. 

Figure 1 shows the primary structure of a protein ingested as part of a mammalian diet. 

Indicate, on Figure 1 , using a cross ( ╳ ) a position that would be cut by an exopeptidase enzyme.

State the two main roles of bile in digestion.

In an experiment examining the rate of reaction of an amylase-catalysed reaction, state and explain the final colour that would be observed from the iodine test in a test tube containing denatured amylase. 

In a different experiment to measure the effect of temperature on the rate of a lipase-catalysed reaction, lipids in the test sample are broken down to fatty acids and glycerol by the action of lipase. Explain why pH is a suitable dependent variable for this experiment and choose one suitable control variable.

The catalytic activity of lipase takes place solely in the ___________. Name this organ of the digestive system. 

Bile emulsifies fats. Explain what ‘emulsifies’ means. 

Name the substance that is also transported when glucose is absorbed. This substance is necessary for effective glucose absorption. 

Identify the structures which are small projections, 0.5 to 1.0 mm long, of the epithelial lining of the small intestine. State their purpose. 

Figure 1 shows a villus. 

Identify structures X and Y and state the organ system to which each structure belongs.

Name the process by which food is pushed along the oesophagus and small intestine.

Describe and explain one property of visking tubing (sometimes called dialysis tubing) that makes it a good choice for experiments that model the action of enzymes in the gut. 

A ‘Model Gut’ experiment was set up as shown in Figure 1 and maintained at 37°C for 30 minutes. 

Predict and explain the result of a starch (iodine) test on the solution outside the visking tubing (in the beaker) after 30 minutes. 

The experiment shown in Figure 1 can be used to measure the effect of pH on amylase activity by setting up tests at various set pH values. Buffer solutions are used in these investigations. Define ‘buffer solutions’ and state their usefulness in such an investigation. 

In the experiment shown in Figure 1 , name a suitable biochemical test to demonstrate the presence of the products of starch digestion in the water surrounding the visking tubing after 30 minutes. 

Washing powders often contain many different types of enzymes that hydrolyse substances in stains. An investigation was carried out on washing powder with and without added enzymes to determine how well it was able to remove stains. Figure 1 shows their results.

The substances that cause the food stains are usually large insoluble proteins. Explain how a biological washing powder removes these stains.

A journalist was investigating the claims by washing powder manufacturers that stated their product removes all tough stains. Figure 1 shows their results. Use the information in Figure 1 to evaluate the manufacturers claim.

The manufacturer of biological washing powder wanted to develop a washing powder that was effective across a range of different temperatures. They investigated the effect of temperature on the rates of reaction catalysed by two enzymes, A and B. Figure 2 shows their results. 

The manufacturer concluded that enzyme B would be the best enzyme to use. Use the results from Figure 2 to evaluate this conclusion. 

Suggest and explain one other factor the manufacturers should consider when deciding on the best enzyme to include in the biological washing powder.

Figure 1 shows a cell commonly found in the small intestine.

Identify organelle C and suggest why there are large numbers of organelle C in these cells.

The structures labelled A can be damaged when people suffer from coeliac disease which is a disease of the human digestive system. They tend to have lower concentrations of amino acids in their blood. 

Explain why they have low concentrations of amino acids in their blood.

Figure 2 shows one of the ways in which amino acids are absorbed from the small intestine into the blood.

Cyanide is an inhibitor of mitochondria. In the presence of cyanide, the concentration of  sodium ions in the cell rises and amino acid absorption stops. 

Explain why sodium ions and amino acids will not be absorbed from the lumen of the small intestine in the presence of cyanide. 

What is the mechanism of movement represented by Q ? Explain your answer.

Scientists investigated if there was a difference in lactase activity in adult mice who were fed different types of carbohydrate diets as newborn mice. The mice were divided into four groups all of which were fed a standard diet only differing in the carbohydrate content. Table 1 shows their results. 

The data is presented with standard deviations for each group. Suggest why the standard deviations differ. 

A group of scientists concluded that increasing glycogen in the diet in adults was the most effective way to increase lactase activity. Evaluate this conclusion.

Lactose is often found in milk with many adults unable to digest lactose and suffering from intestinal problems if they drink milk. Figure 1 shows an industrial reactor used to produce lactose-reduced milk.

Suggest one benefit of immobilising lactase in this reactor. 

Using Figure 1, explain three reasons why the milk must be passed through the reactor several times.

Figure 1 shows some of the events that occur when lipids are digested and absorbed in the small intestine. 

Use Figure 1 to describe how the large lipid droplet is absorbed into the blood stream. 

A group of scientists wanted to investigate the effect of lipase and a 11% bile salts solution on the digestion of triglycerides. Figure 2 shows their results.

Describe and explain the results shown in Figure 2.

The investigation was repeated at a temperature that was 10 C° lower. Sketch on Figure 3 below the graph you would expect to see at this lower temperature for lipase solution with 11% bile salts.

When chylomicrons leave the epithelial cell, they enter small lymphatic capillaries called lacteals. Suggest how chylomicrons leave the epithelial cell and explain your answer. 

Bacteria are often used in industries when scientists need large amounts of enzymes.Describe how bacteria divide and suggest why they are used in industry to provide enzymes.  

Some bacteria are able to secrete proteases outside of their cells. Suggest and explain an advantage of this. 

Mammals can produce extracellular proteases as well as membrane-bound enzymes such as dipeptidases. Explain why dipeptidases are important in protein digestion. 

Endopeptidases are enzymes that hydrolyse the internal peptide bonds found in long polypeptide chains whereas exopeptidases hydrolyze terminal peptide bonds. Soybean and other legumes contain chemicals that inhibit endopeptidases such as trypsin. Explain the effects of these chemicals on protein digestion and absorption.  

Figure 1 below shows part of the human digestive system. The different organs are labelled H - M .

Give the letter of the organ that temporarily stores faeces before egestion.

Name organ L in Figure 1 and the digestive enzyme that it produces.

The glucose concentration in blood rises after eating a meal that contains carbohydrates.

The increase in glucose concentration occurs at a slower rate if the carbohydrate ingested is starch, rather than sucrose. Explain why this is

Glycaemic load (GL) is a measure of how much digestible carbohydrate a person diet contains. A higher GL diet will raise the blood glucose concentration more rapidly after a meal. A high GL diet can also cause the concentration of harmful lipids in the blood to increase.

Lab technicians decided to investigate the relationship between different glycaemic load diets and the risk of developing coronary heart disease (CHD), specifically in women.

The glycaemic loads of the diets of a large number of women were determined by technicians. The women were then divided into 5 groups. Group 1 had the lowest GL diets and group 5 had the highest GL diets. The technicians then determined the risk of developing CHD in each group of women.

Use the information from the question and Figure 2 to describe and explain how the glycaemic load of a diet affects the risk of developing CHD.

Figure 1 below outlines the mechanism of lipid digestion and absorption.

What type of cell is cell A ?

Figure 1 shows the formation of lipid droplet and micelles. Explain the advantages of these structures.

Triglycerides are hydrolyzed by the enzyme lipase.

A student wanted to investigate the breakdown of triglycerides in cow milk by human lipase at 20 °C.

They recorded the pH of a sample of cow’s milk before and after adding human lipase.  They used a pH meter to measure the pH. Their results are shown in figure 2 .

Describe and explain the changes in pH after human lipase is added.

The student carried out his experiment at a controlled temperature of 20 °C. They repeated the experiment at 25 °C.

Draw a line on the graph ( Figure 2 ) to show the results you would expect at 25 °C.

Figure 1 below shows the digestion pathway of proteins. 

Name the missing molecule X and missing enzyme Y .

Describe the different actions of endopeptidases and exopeptidases.

Pancreatitis is a medical condition that can lead to the pancreatic duct becoming blocked. It can also cause protein-digesting enzymes to be released into the bloodstream. Suggest one reason why this might be harmful.

Figure 2 below illustrates the co-transport mechanism for the absorption of amino acids into the blood by a cell lining in the small intestine.

Use Figure 2 and your knowledge of the co-transport mechanism, to explain why epithelial cells in the small intestine contain a large number of mitochondria.

Describe the role that enzymes play in the digestion and complete breakdown of starch.

A lab technician set up the experiment shown in Figure 1 below.

After 20 minutes, the samples were taken from the liquid in the beaker, and from the liquid inside the Visking tubing. Biochemical tests were carried out on these samples. Complete Table 1 by placing an X in each box that you predict will have shown a positive result.

Justify your answers for part (b).

Describe the colour change that takes place for a positive result with Benedict’s solution.

State where bile is produced and stored in the human body.

Bile salts bind to fat droplets and break them down into smaller fat droplets. Explain how this process makes lipid digestion more efficient.

The products of protein and carbohydrate digestion require a co-transporter system for absorption into the epithelial cells of the small intestine. The products of lipid digestion can enter by simple diffusion. 

Explain why this is possible.

Lactose intolerance is a common occurrence in the adult population. An individual who is lactose intolerant no longer produces the enzyme lactase in their ileum. Two students were tested for lactose intolerance. They both fasted for 12 hours before drinking a liquid containing 60 g of lactose. The glucose concentration in their blood was measured for the next 125 mins. The results are shown in Figure 1 below.

Suggest which individual is lactose intolerant. Justify your answer.

• High School

A student carried out an experiment to model the digestion of starch by the enzyme amylase in the small intestine. Visking tubing is a selectively permeable membrane that has small holes in it to allow small molecules to pass through. At regular intervals, the student tested the liquid inside and outside the Visking tube. How could the student test for the presence of starch inside the Visking tubing?

Expert-verified answer.

• 10.9K answers
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Final answer:

The student can test for the presence of starch in the Visking tubing by using iodine solution. If the solution turns blue-black, it indicates the presence of starch. This is part of understanding the role of amylase in digestion.

Explanation:

The student can test for the presence of starch inside the Visking tubing by using an iodine solution. Iodine interacts with starch to produce a blue-black color. The procedure would be to collect a sample from inside the Visking tubing and then add a few drops of iodine solution . If the solution turns from its original yellow-brown color to a blue-black color, it would indicate the presence of starch. However, if the color of the solution stays the same or changes to a different color, it would mean that no starch is present. This experiment helps to understand the digestion process in the human body, specifically the role of amylase in breaking down starch into smaller molecules .

Learn more about Starch detection test here:

brainly.com/question/32559517

• 910 people helped

Put one drop on the dimple tile, and the rest in a test tube. Then put the teat pipette back in the water outside the Visking tubing. Test the drops of liquid in the dimple tile by adding one drop of iodine solution from the dropper bottle. If they turn blue-black, the liquid contains starch.

Explanation: i hope this helped :)

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