1.3 Movement of Substances Into & Out of Cells

A group of scientists investigated the rates of absorption of different sugars using two pieces of the intestine.

One piece of the intestine was poisoned with cyanide which stops cellular respiration.

The results are shown in the table below.

Which of the sugars in the table are absorbed by active transport?

Explain why you chose these sugars, using evidence from the table in part (a).

One of the scientists states ‘All four of the sugars we investigated can be absorbed by diffusion.

Is this statement correct or incorrect? Justify your answer.

One of the sugars absorbed by active transport is glucose.

Xylose is a sugar that is the same size as glucose, but it is not absorbed by active transport.

Suggest a reason why.

A student wanted to investigate the transport of water across a partially permeable membrane. The diagram shows how the student prepared the beaker at the start of the investigation.

Complete the diagram to show what the student would observe after 15 minutes.

Explain your answer to part (a).

The student carried out a further investigation into the effect of osmosis on plant tissue. 

They cut a potato into cubes and recorded the change in mass over a 30 minute period.

The graph shows the results the student obtained from one cube of potato.

Describe and explain the trend shown on the graph.

The potato cube from the graph in part (c) had an initial mass of 2.3g.

Calculate the percentage increase that the potato cube had shown after 10 minutes.

The student repeated the investigation but with the beaker placed in a water bath at 30°C.

Draw a second line on the graph to show the trend expected from these results.

Explain your line drawn for part (e)

Monoglycerides are molecules made up of glycerol and one fatty acid tail. They are absorbed into the epithelial cells of the small intestine by diffusion across the cell membrane.

Some people suffer from coeliac disease that affects the lining of their small intestine.

The diagram compares the lining of the small intestine of a healthy person and a person suffering from coeliac disease.

Based on the information provided, explain the effect that coeliac disease would have on the absorption of monoglycerides.

The graph shows the rate of uptake of monoglycerides in the small intestine.

Describe and explain what the graph shows.

Human body temperature is approximately 37 °C, which provides the optimum temperature for the activity of protein molecules such as enzymes. 

Suggest why a temperature of 37 °C helps to maximise the rate of transport of substances across the cell membrane.

A student investigated the effect of different concentration of sugar solution on osmosis in potato tissue.

This is the method they used:

1. Add 20 cm³ of distilled water to a boiling tube. 
2. Repeat step 1 with equal volumes of 0.2, 0.4, 0.6 and 0.8 mol dm⁻³ sugar solutions.
3. Cut five cylinders of potato of equal size using a cork borer, cutting off the ends to remove the skin.
4. Weigh each potato cylinder and place one in each tube.
5. Remove the potato cylinders from the solutions after 12 hours.
6. Dry each potato cylinder with a paper towel.
7. Reweigh the potato cylinders.

The table below shows the results:

(2)

(1)

The student analysed the data from the experiment.

In the space below, plot a graph of the results from this experiment.

(5)

Use your graph to estimate the concentration of the solution inside the potato cells. 

Give your answer in mol dm^-3.

(1)

Design an investigation to compare the sugar content of sweet potato to the sugar content of normal potato.

Your answer should include experimental details and be written in full sentences.

Figure 1 shows two solutions separated by a partially permeable membrane.

Figure 1

Identify the direction of the net movement of water molecules. Describe your answer using the labels A and B on Figure 1.

(1)

Explain why there is movement of water molecules in this particular direction

(2)

If the membrane shown in Figure 1 was fully permeable explain what would happen to the sucrose molecules.

(2)

During a science lesson a student writes down the following statement about osmosis.

Using your knowledge of osmosis, suggest what is wrong with this statement.

Figure 2 shows two human red blood cells. The cell labelled B had been placed in concentrated salt solution.

Figure 2

Describe the changes to the cell labelled B.

(1)

(ii)

Explain why the cell labelled B has changed shape.

(2)

(iii)

A student placed a sample of red blood cells into pure water for 30 minutes. When they checked the blood/water solution under a microscope they could not identify any intact cells.

Explain what is likely to have happened to the red blood cells after being in water.

(3)

Sugar molecules are moved from the gut to the blood by active transport.

Describe what is involved in active transport?

The bean plant in Figure 1 has a higher concentration of mineral ions in the cells of its roots compared to the concentration of mineral ions in the soil.

Figure 1

Which two statements correctly describe the absorption of mineral ions by the plant's roots.

(2)

The plant will absorb water molecules from the soil into the roots.

Explain why the water moves in this direction.

(2)

Figure 2 shows a molecule (X) that is about to be transported across a cell membrane via active transport. 

Figure 2 

Describe what evidence is shown in Figure 2 that suggests that the process taking place is active transport.

Explain how cells that carry out a lot of active transport may be adapted to their function. 

(1)

Use words from the box to complete the following statements.

Particles in gases and liquids spread by diffusion moving from areas of ________ concentration to areas of ________ concentration. In diffusion, particles move ________ a concentration gradient.

________ is the ________ diffusion of water molecules from a ________ solution to a ________ solution through a partially permeable membrane.

Cells can transport molecules ________ a concentration gradient using ________. This is an ________ process so requires energy.

Figure 1 shows how the uptake of nitrate ions (A) and chloride ions (B) by the roots of a plant varies with oxygen concentration.

Figure 1

Compare the effect of oxygen concentration on the rate of ion uptake for both nitrate ions and chloride ions. 

(4)

With reference to cell transport processes, explain why there is a difference between the rate of uptake of nitrate and chloride ions at different oxygen concentrations.

(5)

Figure 1 lists four features about how particles move across cell membranes.

Figure 1

Complete the empty boxes in Figure 1 with a tick (✓) or a cross (×) depending on whether the feature applies to diffusion, osmosis or active transport. 

A chicken egg is a single cell, surrounded by a cell membrane and protected by an outer shell.

The shell can be removed by dissolving in dilute acid as shown in Figure 2.

Figure 2

A student decided to investigate the effect of different salt solutions on the mass of chicken eggs that were only protected by the cell membrane. They used the following method:

1. Five eggs were placed in acid for 24 hours to dissolve the eggshell as shown in Figure 2

2. The mass of each egg was measured and recorded

3. Eggs were placed in one of five different solutions

4. The solutions ranged in salt concentration from 0 mol dm^-3 to 0.8 mol dm^-3

5. After 60 minutes the eggs were removed, dried and the mass recorded

The results are shown in Figure 3

Figure 3

Explain why in some of the solutions the mass of the eggs decreased.

Explain what the student would need to do to determine an estimate of the concentration of the solution inside an egg.

Figure 1 shows two potato chips.

Figure 1

Figure 2 shows some information about each potato chip.

Figure 2

(2)

total surface area = ....................................... cm²

Figure 1 shows alveoli from a lung.

Figure 1

(3)

Figure 2 shows the movement of molecules across a membrane.

Figure 2

Describe how Figure 2 illustrates movement of molecules across a membrane.

Explain, using Fick’s law, the factors that affect the diffusion rate of molecules into and out of cells.

A student wanted to investigate the movement of water into and out of cells in potatoes.

The student had the equipment shown in Figure 1.

The test tubes in the rack contain different concentrations of sodium chloride solution.

The solutions were 0.1 M, 0.2 M, 0.3 M, 0.4 M and 0.5 M sodium chloride solution.

The test tube in the beaker contains distilled water.

There are three potato chips in each of the six test tubes.

(1)

(2)

(3)

Figure 1 shows some carrot sticks.

Figure 1

A student chose three carrot sticks and weighed each one.

The carrot sticks were placed in 50 cm³ of distilled water.

After two hours the student weighed each carrot stick again.

Figure 2 shows the results for these carrot sticks P, Q and R.

Figure 2

Use the equation

Give your answer to 2 significant figures.

percentage change = .................................................... %