Osmosis

A student investigated osmosis in pieces of potato.

This is the method used.

1. Cut a piece of potato into a cube.

2. Record the mass of the cube.

3. Place the cube into a beaker containing 0.4 mol/dm³ salt solution.

4. After some time, remove the cube and record the mass.

5. Calculate the change in the mass of the cube.

6. Repeat steps 1 to 5 using two more different concentrations of salt solution.

Evaluate the student’s method.

You should include how the student could improve the validity of their results.

Why would a potato cube placed into distilled water increase in mass?

Tick () one box.

Active transport is another process used by potato cells.

Give one way active transport is different from osmosis.

A student investigated osmosis in pieces of potato.

This is the method used.

1. Cut a piece of potato into a cube.

2. Record the mass of the cube.

3. Place the cube into a beaker containing 0.4 mol/dm³ salt solution.

4. After some time, remove the cube and record the mass.

5. Calculate the change in the mass of the cube.

6. Repeat steps 1 to 5 using two more different concentrations of salt solution.

Evaluate the student’s method.

You should include how the student could improve the validity of their results.

Why would a potato cube placed into distilled water increase in mass?

Tick () one box.

Active transport is another process used by potato cells.

Give one way active transport is different from osmosis.

A student investigated the effect of different concentrations of salt solution on the mass of uncooked pieces of potato.

This is the method used.

1. Cut four pieces of a potato to the same size.

2. Record the mass of each piece of potato.

3. Put one of the pieces of potato into a beaker containing 100 cm³ of 0.1 mol/dm³ salt solution.

4. Repeat step 3 using the other pieces of potato, each in a different concentration of salt solution.

5. After 20 minutes, remove the pieces of potato from the solutions.

6. Record the mass of each piece of potato.

Give two control variables the student used in the investigation.

The student needed to be sure the measurements were as accurate as possible.

What should be done to each piece of potato after removing from the solution and before measuring the mass?

Name the piece of apparatus the student could use to measure the mass of the pieces of potato.

Table 4 shows the results.

What was the resolution of the apparatus used for measuring mass?

Use Table 4.

Tick () one box.

Which piece of potato had the greatest change in mass in the investigation?

Tick () one box.

Calculate value X in Table 4.

Use the equation:

Give your answer to 1 decimal place.

What is the best way to present the data in Table 4 ?

Tick () one box.

Complete the sentences.

Some of the pieces of potato decreased in mass because the potato cells

The structure surrounding each cell in a piece of potato is

Table 4 is repeated below.

Estimate the concentration of salt solution that would not cause a change in mass of these pieces of potato.

A student investigated the effect of concentration of salt solution on the mass of uncooked potato pieces.

Figure 4 shows the results.

Plan a method that could be used to obtain the results in Figure 4.

Explain the result for the potato pieces in the 0.6 mol/dm³ salt concentration.

Explain why the result for the potato pieces at 1.0 mol/dm³ was different from the

Plants are made of cells, tissues and organs.

Which part of a plant is the largest?

Tick (✓) one box.

Students investigated the effect of concentration of salt solution on the mass of pieces of potato.

This is the method used.

1. Cut two pieces of potato to the same size.

2. Record the mass of each piece of potato.

3. Place one piece of potato into a beaker containing a dilute salt solution.

4. Place the other piece of potato into a beaker containing a concentrated salt solution.

5. After 20 minutes, remove each piece of potato from its solution.

6. Record the change in mass of each piece of potato.

7. Repeat steps 1 to 6 two more times.

Table 1 shows the results.

Calculate mean value X in Table 1.

There is an anomalous result for the concentrated salt solution in Table 1.

Draw a ring around the anomalous result in Table 1.

What did the students do with the anomalous result when calculating the mean in Table 1 ?

What name is given to a variable that is kept the same during an investigation?

Tick (✓) one box.

One variable the students kept the same during the investigation was the size of the pieces of potato.

Which other variable did the students keep the same?

Tick (✓) one box.

The pieces of potato in the concentrated salt solution decreased in mass.

Complete the sentence.

Choose the answer from the box.

The potato cells have a partially permeable membrane.

Which particles can pass through a partially permeable membrane?

Tick (✓) one box.

How could the students improve their investigation?

Tick (✓) one box.

Salmonella bacteria cause outbreaks of food poisoning in humans. To prevent food poisoning in humans, farmers vaccinate their animals against Salmonella bacteria.

How do Salmonella bacteria in food cause the symptoms of vomiting and diarrhoea?

During a food poisoning outbreak, scientists identified the farm where the food came from. The farmer had not vaccinated the farm animals against Salmonella bacteria.

The food poisoning outbreak could have been prevented if the farm animals had been vaccinated. Explain how:

• the immune systems of animals respond to a vaccination

• the immune response in farm animals prevents an outbreak of food poisoning in humans.

Most cases of food poisoning do not need to be treated with antibiotics. However, some patients may need to take antibiotics to recover. Scientists investigated the effectiveness of five different antibiotics on the Salmonella bacteria in the outbreak. Antibiotics A, B, C, D and E were used in the investigation. Figure 4 shows the results.

Describe two aseptic techniques the scientists should have used in the investigation.

The scientists incubated the bacteria at 37 °C. Students in school laboratories incubate bacteria at 25 °C. Explain why scientists use 37 °C but students must use 25 °C to incubate bacteria.

What is the purpose of the paper disc with no antibiotic in Figure 4 ?

The scientists concluded that either antibiotic A or antibiotic B should be prescribed to patients with food poisoning. Why should antibiotic A or antibiotic B be prescribed?

The scientists wanted to be more certain about which antibiotic should be prescribed. Describe how the results in Figure 4 could be used to obtain a quantitative comparison of antibiotics A and B.

One year later, there was another outbreak at the farm involving Salmonella bacteria. Antibiotic B did not have an effect. Suggest why antibiotic B no longer had an effect.

Antibiotics treat food poisoning because they kill Salmonella bacteria inside the human body. Some antibiotics work because they damage the bacterial cell wall. The bacteria die because the cells burst. Explain why the cells burst.

This question is about cells and transport.

Complete Table 5.

Cells in potatoes are plant cells.

Cells in potatoes do not contain chloroplasts.

What is the function of chloroplasts?

Name one type of cell in a potato plant that does not contain chloroplasts.

A student investigated the effect of salt concentration on pieces of potato.

This is the method used.

1. Cut three pieces of potato of the same size.

2. Record the mass of each potato piece.

3. Add 150 cm³ of 0.4 mol/dm³ salt solution to a beaker.

4. Place each potato piece into the beaker.

5. After 30 minutes, remove each potato piece and dry the surface with a paper towel.

6. Record the mass of each potato piece.

7. Repeat steps 1 to 6 using different concentrations of salt solution.

What is the independent variable in the investigation?

Tick (✓) one box.

Why did the student dry the surface of each potato piece with a paper towel in step 5 ?

The student calculated the percentage change in mass of each potato piece.

For one potato piece:

• the starting mass was 2.5 g

• the end mass was 2.7 g.

Calculate the percentage increase in mass of the potato piece.

Use the equation:

The student used the results from each potato piece to calculate the mean percentage change in mass at each concentration.

Table 6 shows the results.

Complete Figure 9.

You should:

• label the x-axis

• use a suitable scale for the x-axis

• plot the data from Table 6

• draw a line of best fit.

What concentration of salt solution was equal to the concentration of the solution inside the potato pieces?

Use Figure 9.

Explain why the potato pieces in the 0.4 mol/dm³ salt solution decreased in mass.

This question is about cells and transport.

Complete Table 1.

Cells in potatoes are plant cells. Cells in potatoes do not contain chloroplasts.

What is the function of chloroplasts?

Name one type of cell in a potato plant that does not contain chloroplasts.

A student investigated the effect of salt concentration on pieces of potato. This is the method used.

1. Cut three pieces of potato of the same size.

2. Record the mass of each potato piece.

3. Add 150 cm³ of 0.4 mol/dm³ salt solution to a beaker.

4. Place each potato piece into the beaker.

5. After 30 minutes, remove each potato piece and dry the surface with a paper towel.

6. Record the mass of each potato piece.

7. Repeat steps 1 to 6 using different concentrations of salt solution.

What is the independent variable in the investigation? Tick (✓) one box.

Why did the student dry the surface of each potato piece with a paper towel in step 5 ?

The student calculated the percentage change in mass of each potato piece.

For one potato piece:

• the starting mass was 2.5 g

• the end mass was 2.7 g.

Calculate the percentage increase in mass of the potato piece. Use the equation:

The student used the results from each potato piece to calculate the mean percentage

change in mass at each concentration. Table 2 shows the results.

Complete Figure 1. You should:

• label the x-axis

• use a suitable scale for the x-axis

• plot the data from Table 2

• draw a line of best fit.

What concentration of salt solution was equal to the concentration of the solution inside the potato pieces? Use Figure 1.

Explain why the potato pieces in the 0.4 mol/dm³ salt solution decreased in mass.

A student prepared some animal cells to view using a microscope. Figure 14 shows the student preparing the cells.

Name two pieces of laboratory equipment the student could have used to prepare cells to view using a microscope.

Figure 15 shows the student’s light microscope.

Name part A.

What is the function of part B ?

The student tried to look at the cells using the microscope. Suggest one reason why the student could not see any cells when looking through part A.

Red blood cells are specialised animal cells. Compare the structure of a red blood cell with the structure of a plant cell.

When placed into a beaker of water:

• a red blood cell bursts

• a plant cell does not burst.

Explain why the red blood cell bursts but the plant cell does not burst.

A student prepared some animal cells to view using a microscope.

Figure 1 shows the student preparing the cells.

Name two pieces of laboratory equipment the student could have used to prepare cells to view using a microscope.

Figure 2 shows the student’s light microscope.

Name part A.

What is the function of part B ?

The student tried to look at the cells using the microscope.

Suggest one reason why the student could not see any cells when looking through part A.

Red blood cells are specialised animal cells.

Compare the structure of a red blood cell with the structure of a plant cell.

When placed into a beaker of water:

• a red blood cell bursts

• a plant cell does not burst.

Explain why the red blood cell bursts but the plant cell does not burst.

Diffusion is an important process in animals and plants.

What is meant by the term diffusion?

Figure 2 shows part of a leaf.

Molecules of carbon dioxide diffuse from the air into the mesophyll cells. Which two changes will increase the rate at which carbon dioxide diffuses into the mesophyll cells? Tick (✓) two boxes.

Diffusion also happens in the human lungs. Figure 3 shows the human breathing system.

Explain how the human lungs are adapted for efficient exchange of gases by diffusion.

Figure 4 shows a root hair cell.

Name the process by which water molecules enter the root hair cell.

Nitrate ions need a different method of transport into the root hair cell. Explain how the nitrate ions in Figure 4 are transported into the root hair cell. Use information from Figure 4 in your answer.

Many foods contain carbohydrates.

Figure 1 shows information about four different foods.

Which food contains the highest percentage of carbohydrate?

Tick (✓) one box.

Estimate the percentage of water found in beans.

Look at Figure 1.

Why would eating only beans provide a more balanced diet than eating only chicken?

Sugars are produced when enzymes break down starch.

What is the name of the enzyme which breaks down starch to produce sugars?

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Which chemical could be used to test for glucose?

Tick (✓) one box.

What colour change would be seen in a positive test for glucose?

From blue to.

People with diabetes have difficulty controlling the concentration of glucose in their blood.

The blood of four people was tested.

Table 1 shows the results.

Table 2 shows the information used to help decide if a person has diabetes.

Which person has severe diabetes?

Tick (✓) one box.

Figure 2 shows part of the human digestive system.

Glucose is absorbed into the bloodstream in part X.

Name part X.

Complete the sentences.

Choose answers from the box.

Some glucose is absorbed into the bloodstream against the concentration gradient by

the process of.

Water moves out of part Y and into the bloodstream by

the process of.

People with diabetes have difficulty controlling their blood glucose concentration.

Which part of the blood transports glucose?

Tick (✓) one box.

Glucose is often found in the urine of people with diabetes.

Name a chemical used to test for glucose.

Describe a test that could be used to show that a person’s urine contains glucose.

The body cells of a person with untreated diabetes lose more water than the body cells of a person who does not have diabetes.

Explain how diabetes can cause the body cells to lose more water.

Glucose is absorbed into the blood in the small intestine by both diffusion and active transport.

Describe how the small intestine is adapted for efficient absorption.

A student carried out an investigation using chicken eggs.

This is the method used.

1. Place 5 eggs in acid for 24 hours to dissolve the egg shell.

2. Measure and record the mass of each egg.

3. Place each egg into a separate beaker containing 200 cm³ of distilled water.

4. After 20 minutes, remove the eggs from the beakers and dry them gently with a paper towel.

5. Measure and record the mass of each egg.

Table 4 shows the results.

Another student suggested that the result for egg 4 was anomalous.

Do you agree with the student?

Give a reason for your answer.

Calculate the percentage change in mass of egg 3.

Explain why the masses of the eggs increased.

Explain how the student could modify the investigation to determine the concentration of the solution inside each egg.

Chicken egg shells contain calcium. Calcium ions are moved from the shell into the cytoplasm of the egg.

Table 5 shows information about the concentration of calcium ions.

Explain how calcium ions are moved from the shell into the cytoplasm of the egg.