Digestion

Drinks contain different substances.

A drinks company claims that a drink contains sugar, protein and fat.

Glucose and fructose are different sugars.

Fructose has a much sweeter taste than glucose.

Suggest two reasons why the drinks company uses fructose in the drink rather than using glucose.

Do not refer to sweetness in your answer.

Describe how a student could test the drink for sugar.

Give the colour of a positive result.

Colour of positive result

Describe how a student could test the drink for protein.

Give the colour of a positive result.

Colour of positive result

The human digestive system breaks down protein and fat in the drink.

Describe how protein and fat are digested.

You should include:

• the enzymes involved

• where the enzymes are produced.

Drinks contain different substances.

A drinks company claims that a drink contains sugar, protein and fat.

Glucose and fructose are different sugars.

Fructose has a much sweeter taste than glucose.

Suggest two reasons why the drinks company uses fructose in the drink rather than using glucose.

Do not refer to sweetness in your answer.

Describe how a student could test the drink for sugar.

Give the colour of a positive result.

Colour of positive result

Describe how a student could test the drink for protein.

Give the colour of a positive result.

Colour of positive result

The human digestive system breaks down protein and fat in the drink.

Describe how protein and fat are digested.

You should include:

• the enzymes involved

• where the enzymes are produced.

Enzymes break down food in the digestive system.

Figure 2 shows the human digestive system.

The enzyme amylase digests starch.

Which part of the digestive system produces amylase?

Tick (✓) one box.

What molecules are produced when starch is digested?

Tick (✓) one box.

Where is digested food absorbed into the blood?

Tick (✓) one box.

Question 2 continues on page 9

A student investigated the effect of pH on the digestion of starch by amylase.

This is the method used.

1. Put 1 drop of iodine solution into each well of a spotting tile.

2. Prepare amylase solution at pH 5

3. Mix the amylase solution with starch solution in a test tube.

4. Every 30 seconds remove a drop of the amylase–starch mixture. Add each drop to iodine solution in a different well of the spotting tile.

5. Record the colour of the iodine solution after the amylase–starch mixture has been added.

6. Repeat steps 2 to 5 using amylase solutions at different pH values.

What is the independent variable in this investigation?

Tick (✓) one box.

Figure 3 shows the results on the spotting tile.

What colours do the symbols in the key represent?

Choose answers from the box.

Look at the results for pH 6 in Figure 3.

How many minutes did it take for all the starch to be digested at pH 6?

What was the optimum pH for the amylase to work?

Use Figure 3.

Tick (✓) one box.

Amylase is an enzyme that digests starch in the digestive system.

Explain why starch has to be digested.

A student used a colorimeter to investigate the rate of starch digestion.

A colorimeter measures the percentage of light passing through a liquid.

The darker the colour of the liquid, the less light passes through.

The student:

• mixed 1 cm³ of starch suspension with 10 cm³ of iodine solution

• measured the percentage of light passing through the mixture

• repeated with different concentrations of starch suspension.

Figure 7 shows the results.

Suggest what liquid was used for the test with 0 g/dm³ starch concentration.

Explain the change in the percentage of light passing through the different concentrations of starch suspension in iodine solution.

Use Figure 7.

Question 6 continues on page 21

The student then investigated the rate of starch digestion using amylase.

This is the method used.

1. Put 10 cm³ of starch suspension into a test tube.

2. Put 5 cm³ of amylase solution into a separate test tube.

3. Put both test tubes into a water bath at 37 °C for 10 minutes.

4. Mix the contents of both test tubes together in a beaker.

5. Put the beaker into the water bath.

6. Remove 1 cm³ of the mixture and add it to 10 cm³ of iodine solution.

7. Measure the percentage of light passing through the liquid.

8. Repeat steps 6 and 7 every minute for 5 minutes.

The starch suspension and the amylase solution were kept in the water bath for 10 minutes before being mixed together.

Give the reason why.

Figure 8 shows the results.

The concentration of starch at 3 minutes was 0.3 g/dm³.

Calculate the mean rate of starch digestion for the first 3 minutes.

Use Figure 7 on page 18 and Figure 8 on page 22.

The investigation was carried out at pH 7

Explain how the results would be different if the investigation was carried out at pH 1

Use Figure 8.

Foods are digested before they are absorbed into the blood.

Figure 1 shows organs in the human digestive system.

Which organ is the stomach?

Tick (✓) one box.

What type of enzyme is produced in the stomach?

Tick (✓) one box.

Which term describes the pH in the stomach?

Give one reason why the stomach is this pH.

Tick (✓) one box.

Which organ produces bile?

Tick (✓) one box.

How does bile help in the digestion of foods?

Tick (✓) one box.

A student tested different foods for the presence of protein, starch and sugar.

Draw one line from each food molecule to the reagent used to test for the food molecule.

Food molecule
Reagent

Give one safety precaution a student should take when using Benedict’s solution.

Table 1 shows the results for one food sample.

Which of the tests show positive results?

Tick (✓) one box.

Starch molecules are not absorbed into the blood from the digestive system.

Give one reason why.

Amylase is an enzyme that digests starch.

Which organs in the human digestive system produce amylase? Tick (✓) one box.

A student investigated the effect of pH on the activity of amylase. This is the method used.

1. Prepare amylase solution at pH 5

2. Mix the amylase solution with starch in a boiling tube.

3. Remove a drop of the amylase-starch mixture every 30 seconds and test it for the presence of starch.

4. Record the time when all the starch has been digested.

5. Repeat steps 1 to 4 using amylase solution prepared at pH 6, then at pH 7 and

then at pH 8

What was the independent variable in this investigation?

Describe how the student would know when all the starch had been digested.

Figure 6 shows the student’s results.

What was the optimum pH for the amylase? Use Figure 6.

A scientist did a different investigation. This is the method used.

1. Prepare amylase solution at the optimum pH.

2. Mix the amylase solution with starch in a boiling tube.

3. Measure the concentration of sugar every 10 seconds for 2 minutes.

Figure 7 shows the scientist’s results.

How much time did it take for the amylase to digest all the starch? Use Figure 7.

Determine the rate of sugar production per minute at 40 seconds.

Explain how the structure of enzyme molecules is related to the effect of pH on the activity of amylase.

Describe how to test a sample of food for protein, starch and sugar.

Give the colours that would be seen if the food sample contained protein, starch and sugar.

Describe how to test a sample of food for protein, starch and sugar. Give the colours that would be seen if the food sample contained protein, starch and sugar.

Starch is digested to form sugar molecules in the digestive system.

What is the name of the enzyme that digests starch?

Where are most food molecules absorbed? Tick (✓) one box.

Figure 6 shows two villi. Figure 6 also shows one cell on the surface of a villus as seen using an electron microscope.

Give one advantage of using an electron microscope compared with using a light microscope.

What type of blood vessel is labelled X ? Tick (✓) one box.

The real length of one villus is 0.8 mm Calculate the image length if the villus is viewed at a magnification of ×20 Use the equation:

Figure 7 shows two cells from the surface of a villus. There are sugar molecules inside and next to each cell.

Name the process by which sugar moves into cell A.

Name the process by which sugar moves into cell B.

Give one use of sugar in the body.

Figure 6 is repeated below.

Explain how villi are adapted for efficient absorption of sugar molecules.

Starch is digested to form sugar molecules in the digestive system.

What is the name of the enzyme that digests starch?

Where are most food molecules absorbed? Tick (✓) one box.

Figure 2 shows two villi. Figure 2 also shows one cell on the surface of a villus as seen using an electron microscope.

Give one advantage of using an electron microscope compared with using a light microscope.

What type of blood vessel is labelled X ? Tick (✓) one box.

The real length of one villus is 0.8 mm Calculate the image length if the villus is viewed at a magnification of ×20 Use the equation:

Figure 3 shows two cells from the surface of a villus. There are sugar molecules inside and next to each cell.

Name the process by which sugar moves into cell A.

Name the process by which sugar moves into cell B.

Give one use of sugar in the body.

Figure 2 is repeated below.

Explain how villi are adapted for efficient absorption of sugar molecules.

This question is about digestion.

Name the enzyme that digests starch in the human digestive system.

A student set up a model to represent the digestion and absorption of food molecules in the digestive system.

Figure 11 shows the student’s model.

This is the method used.

1. Fill a test tube with water at 37 °C

2. Test the water for starch and for sugar.

3. Mix together starch and enzyme solution and immediately test it for starch and for sugar.

4. Fill some partially permeable tubing with the starch and enzyme mixture.

5. Seal the tubing and place it in the test tube of water.

6. Place the test tube in a water bath at 37 °C

7. After 30 minutes, test the mixture inside the partially permeable tubing and test the water in the test tube for starch and for sugar.

Suggest which parts of the body the partially permeable tubing and the water in the test tube represent.

Partially permeable tubing

Water in the test tube

Table 3 shows the results.

✗ = Not present

Name the reagents used to test for starch and for sugar.

Why was there no sugar present in test 1 ?

Explain the results for test 3.

Explain the results for test 4.

This question is about digestion.

Name the enzyme that digests starch in the human digestive system.

A student set up a model to represent the digestion and absorption of food molecules in the digestive system. Figure 2 shows the student’s model.

This is the method used.

1. Fill a test tube with water at 37 °C

2. Test the water for starch and for sugar.

3. Mix together starch and enzyme solution and immediately test it for starch and for sugar.

4. Fill some partially permeable tubing with the starch and enzyme mixture.

5. Seal the tubing and place it in the test tube of water.

6. Place the test tube in a water bath at 37 °C

7. After 30 minutes, test the mixture inside the partially permeable tubing and test the water in the test tube for starch and for sugar.

Suggest which parts of the body the partially permeable tubing and the water in the test tube represent.

Partially permeable tubing Water in the test tube

Table 2 shows the results.

= Not present

Name the reagents used to test for starch and for sugar.

Why was there no sugar present in test 1 ?

Explain the results for test 3.

Explain the results for test 4.