Osmosis

Figure 17 shows a beaker containing a potato cylinder in distilled water.

Explain why the mass of this potato cylinder will change when it is placed in distilled water.

A scientist investigated the rate of diffusion using three agar cubes of different sizes.

Each cube contained a pH indicator that changed from pink to colourless when placed in acid.

The cubes were placed in a beaker containing an acid.

Figure 18 shows some information about each cube.

Calculate the volume of cube C.

Explain the difference in the times taken for cubes A and B to become colourless.

* (c) Liquid agar was poured into a Petri dish and allowed to set.

A well was cut in the centre of the set agar.

Kiwi fruit juice was poured into the well.

Kiwi fruit juice contains an enzyme that causes set agar to break down into a liquid.

Figure 19 shows the results after 30 minutes.

Devise a plan to investigate the effect of different concentrations of kiwi fruit juice on the breakdown of set agar, using the equipment shown in Figure 19.

Your plan should include:

• measurements that need to be taken

• variables that need to be controlled.

Figure 3 shows a beaker containing a potato cylinder in distilled water.

Explain why the mass of this potato cylinder will change when it is placed in distilled water.

A scientist investigated the rate of diffusion using three agar cubes of different sizes.

Each cube contained a pH indicator that changed from pink to colourless when placed in acid.

The cubes were placed in a beaker containing an acid.

Figure 4 shows some information about each cube.

Calculate the volume of cube C.

Explain the difference in the times taken for cubes A and B to become colourless.

In 2018, all the plants were removed from the soil in a 1000 m² area.

A wall was built around this area to keep people out.

In 2019, three species of plants were recorded growing in this area.

Two of these species were indigenous.

State what is meant by the term ’indigenous’.

Name one piece of equipment that could be used to sample the number of indigenous plants in this area.

The area was surveyed every year and the number of plants of each species (A to H) was estimated.

Figure 6 shows the results.

State the trend shown by the data in Figure 6 for plant species C from 2019 to 2023.

A scientist suggested that the decrease in the number of plants of species B in 2021 was caused by competition from one of the other species of plant.

Which species is most likely to have out-competed species B in 2021?

Explain one way that this species could have out‑competed species B.

Give one way that species H could have moved into the area.

Plants also need water to grow.

Explain how water is absorbed into the plant.

Figure 13 shows a root hair cell from a plant.

Name the part labelled X.

State one way that the structure of the root hair cell increases the volume of substances it absorbs.

Explain why root hair cells do not contain chloroplasts.

*(c) The arrows in Figure 15 show the direction of water movement through a tree.

Explain how water is moved from the soil, through the plant and into the air.

3 (a) Figure 2 shows a root hair cell from a plant.

(i) Name the part labelled X.

(ii) State one way that the structure of the root hair cell increases the volume of substances it absorbs.

(iii) Explain why root hair cells do not contain chloroplasts.

from the Elodea cells in tap water.

(ii) Explain why placing the Elodea cells in the 10% salt solution causes the changes seen in Figure 3.

A student investigated the movement of water in potatoes.

The student used three identical cubes of potato.

The size of a cube is shown in Figure 12.

Calculate the volume of this cube.

Include the units in your answer.

One cube was placed in water and each of the other two cubes were placed in solutions with different concentrations of salt.

The cubes were left for 20 minutes.

Figure 13 shows the student’s results.

Give one way the student could ensure the measurement of the mass of the cubes is accurate.

Explain the mass change in the cube in the concentrated salt solution.

The student wanted to find the concentration of salt solution where the potato cube did not change mass.

Describe how the student could modify this investigation to find this concentration.

Explain why potato cells do not burst when placed in water.

8 People with diabetes cannot always control the concentration of glucose in their blood.

(a) Two people eat identical meals. One person has diabetes, the other person does not have diabetes. Figure 15 shows the concentration of glucose in the blood of these two people after eating the meals.

time after eating the meal in hours

Figure 15

(i) Describe two differences in the concentration of glucose in the blood of the two people shown in Figure 15.

(ii) Calculate the maximum increase in the concentration of glucose in the blood of the person with diabetes.

(iii) Water moved out of the red blood cells of the person with diabetes when the concentration of glucose in the blood was above 15 mmol per dm³. Explain why water moved out of the red blood cells of the person with diabetes.

(b) The pancreas produces a hormone that causes the concentration of glucose in the blood to decrease.

(i) Name this hormone.

(ii) State how this hormone is transported from the pancreas to its target organs.

(iii) Which is the target organ for the hormone that controls the concentration of glucose in the blood?

(c) Explain how type 2 diabetes can be controlled.

People with diabetes cannot always control the concentration of glucose in their blood.

Two people eat identical meals.

One person has diabetes, the other person does not have diabetes.

Figure 4 shows the concentration of glucose in the blood of these two people after eating the meals.

Figure 4

Calculate the maximum increase in the concentration of glucose in the blood of the person with diabetes.

Water moved out of the red blood cells of the person with diabetes when the concentration of glucose in the blood was above 15 mmol per dm³.

Explain why water moved out of the red blood cells of the person with diabetes.

The pancreas produces a hormone that causes the concentration of glucose in the blood to decrease.

Name this hormone.

State how this hormone is transported from the pancreas to its target organs.

Which is the target organ for the hormone that controls the concentration of glucose in the blood?

Explain how type 2 diabetes can be controlled.

4 (a) Figure 5 shows some onion cells that have been soaked in a concentrated salt solution.

(Source: © Rattiya Thongdumhyu/Shutterstock)

Figure 5

(i) The cells in Figure 5 have been stained. Give one reason why the cells have been stained.

(ii) Which is the name of the structure labelled V?

(iii) The salt solution outside the cell has a higher concentration than the solution inside the cell. Explain why the cytoplasm shrinks away from the sides of the cell when the cells are in salt solution.

(b) Figure 6 shows the equipment used to prepare a microscope slide of onion cells.

Describe how this equipment could be used to prepare a slide of onion cells to view under a microscope.

(c) A student investigated the percentage change in mass of potato cylinders placed in sucrose solutions of different concentrations. Figure 7 shows the results of the student’s investigation.

concentration of sucrose solution in mol/dm³

Figure 7

State two conclusions that can be made from these results.

5 (a) Carrots have different physical characteristics such as colour. Which genetic term describes the physical characteristics of a carrot?

(b) Figure 10 shows some carrot sticks.

(Source: © rukxstockphoto/Shutterstock)

Figure 10

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

Figure 11

(i) Give one reason why the student used three carrot sticks instead of just one carrot stick.

(ii) Give two ways that this method could be improved.

(iii) Calculate the percentage change in mass of carrot stick Q.

Use the equation

Give your answer to 2 significant figures.

percentage change =_{..............................................................}

(iv) Explain the change in mass of the carrot sticks.

9 (a) Figure 13 shows a sperm cell.

Figure 13

Describe how structure A and structure B enable fertilisation.

structure A

structure B

(b) Figure 14 shows a human egg cell, magnified ×700.

(Source: © Pascal Goetgheluck / Science Photo Library)

Figure 14

Calculate the actual width of the region indicated by the line on Figure 14. Give your answer in millimetres, in standard form.

* (c) A student investigated the movement of water. Hens’ eggs were placed in vinegar for two days to dissolve the shell. This makes the eggs permeable to water. The eggs were then weighed and placed in different solutions. After 24 hours the eggs were weighed again. Figure 15 shows the results.

Figure 15

Evaluate the results of this investigation. You should include calculations using the data in Figure 15.

Figure 9 shows the structure and actual size of red blood cells (erythrocytes).

red blood cells side view of red blood cell (cut)

(Source: © N.Vinoth Narasingam/Shutterstock)

Figure 9

Calculate the image size of the top view of this red blood cell if this cell is

Give your answer in mm.

Explain how the shape of a red blood cell is related to its function.

State the role of haemoglobin inside the red blood cell.

Some blood transfusions contain red blood cells.

Red blood cells are stored in a solution containing 5.0% glucose and 0.9% salt.

Explain why red blood cells cannot be stored in pure water.

Figure 6 shows a root hair cell from a strawberry plant.

Label the cell vacuole in Figure 6.

Explain how the structure of root hair cells increases water absorption from the soil.

Figure 7 shows fungus growing on strawberries.

The fungus is decomposing the strawberries.

A scientist investigated the effect of temperature on the decomposition of strawberries.

The scientist spread fresh strawberries on six trays.

Each tray was kept at a different temperature.

After five days the scientist measured the area of fungus that had grown on each tray of strawberries.

The results are shown in Figure 8.

The mean rate of growth of fungus at 25C was 12 cm² per day.

Calculate the mean rate of growth of fungus at 30C.

_........ cm² per day

State the effect of temperature on the growth of fungus on strawberries from 5C to 30C.

Decomposition of strawberries can be prevented by boiling the strawberries with sugar to make jam.

Enzymes in the fungus caused decomposition.

Explain how boiling stops the enzymes from working.

Cells from a fungus can land on jam.

The sugar solution inside the jam is more concentrated than the sugar solution inside the fungus cells.

State how osmosis causes the fungus cells to die.

Figure 10 shows a plant cell as seen under a light microscope.

(Source: © HERVE CONGE, ISM/SCIENCE PHOTO LIBRARY)

Figure 10

Draw this plant cell in the box below.

Label three parts of this cell.

Mitochondria cannot be seen with a light microscope.

What is the function of mitochondria in a plant cell?

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

The student had the equipment shown in Figure 11.

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.

State why the test tube in the beaker only contains distilled water and three potato chips.

State two variables that need to be controlled in this investigation.

Explain why the chips in the 0.5 M sodium chloride solution lost mass.

Figure 11 shows two potato chips.

Figure 12 shows some information about each potato chip.

Calculate the total surface area of potato chip B using the formula,

Total surface area = 2XY + 2XZ + 2YZ

The potato chips were placed in distilled water for 20 minutes.

Figure 13 shows the increase in mass of each potato chip.

Explain why potato chip B has a greater increase in mass than potato chip A.

Potato chip A is transferred from the distilled water into a concentrated salt solution.

Explain what will happen to the cells in potato chip A.

*(b) Figure 14 shows two varieties of potato plant.

• large potatoes • small potatoes

• few potatoes • many potatoes

• slow growing plant • fast growing plant

Figure 14

New varieties of potato plant can be produced by selective breeding.

Explain how selective breeding of the two varieties of potato plants can produce new potato plants that are all faster growing and produce many, large potatoes.

(a) Figure 5 shows two potato chips.

Figure 6 shows some information about each potato chip.

Calculate the total surface area of potato chip B using the formula,

Total surface area = 2XY + 2XZ + 2YZ

The potato chips were placed in distilled water for 20 minutes.

Figure 7 shows the increase in mass of each potato chip.

Explain why potato chip B has a greater increase in mass than potato chip A.

Potato chip A is transferred from the distilled water into a concentrated salt solution.

Explain what will happen to the cells in potato chip A.

The potatoes of a potato plant develop underground.

Explain one difference in the sub-cellular structures in a cell in the potato and those in a cell in the leaf of the potato plant.