Cells & Movement Across Membranes (WJEC GCSE Science (Double Award): Biology): Exam Questions

Cerys makes a slide of her cheek cells. One stage in her method is shown in Image 3.1.

Image 3.1

Using the labels on Image 3.1 describe what Cerys is doing at this stage of her method.

Image 3.2 shows a light microscope.

Image 3.2

The lowest magnification of the microscope is ×100.

Calculate the highest magnification of the microscope shown in Image 3.2.

Highest magnification = × ..........................................

Cerys drew and labelled a cheek cell. This is shown in Image 3.3.

Image 3.3

Complete the table below.

Cerys put a drop of stain on the slide before adding her cheek cells.

State the purpose of staining the cells.

(i) Using this light microscope, it is not possible to see the mitochondria even at the highest magnification. State the reason for this.

[1]

(ii) Complete the following sentence by underlining the correct word from the brackets.

[1]

The mitochondria can be seen using an (electronic / electron / electric) microscope.

Image 6.1 represents the lock and key model of enzyme action involving lipase and milk fat.

Image 6.1

State the name of:

(i) structure A;

...................................................................................................

[1]

(ii) molecule B.

...................................................................................................

[1]

A class of students investigated how lipase activity changes with temperature.

They used a pH indicator that is pink in alkaline solutions of about pH 10. When the pH drops below pH 8 it goes colourless.

A solution of full-fat milk, lipase and indicator at pH 10 will change from pink to colourless as the fat in milk is broken down producing fatty acids. This reduces the pH to below 8. The time taken for this reaction to occur is affected by temperature.

The students worked in pairs and set up the apparatus as shown in Image 6.2.

Image 6.2

Each pair of students investigated a different temperature.

• The test tube and syringe were placed in a water bath.

• At 5 minutes, 1 cm3 of lipase solution from the syringe was added to the test tube.

• The time taken for the solution in the test tube to change from pink to colourless was recorded.

• The experiment was carried out three times for each temperature.

The class results are shown in Table 6.3.

Table 6.3

(i) The mean time for each temperature can be converted to rate of reaction by calculating 1 ÷ mean time.

Complete Table 6.3 by calculating the rate of reaction at 60 °C. Give your answer to 2 decimal places.

[1]

(ii) On the grid below, draw a line graph of rate of reaction against temperature.

You should join the plots with a ruler.

[4]

(iii) Describe the effect of temperature on the rate of reaction of lipase.

[1]

(iv) Explain the effect of temperature on the rate of reaction between 0°C and 40°C.

[2]

State why the test tube and syringe were left in the water bath for 5 minutes before the lipase solution was added to the test tube.

Suggest why skimmed milk could not be used in this experiment.

Image 3.1A and 3.1B are photographs taken down a light microscope. Both groups of cells have been treated with biological stains. One of the animal cells (a human cheek cell) has been drawn below its photograph.

(i) Choose one plant cell from Image 3.1B and draw it in the space below Image 3.1B. Label any two parts of the plant cell shown in your drawing. You must not draw or label anything that cannot be seen in the photograph. Do not colour or shade your drawing.

[3]

(ii) State why the cells were treated with biological stains.

[1]

(iii)

I. Measure the length of cell Y along the line X–X and record it below.

[1]

Length of cell Y along line X–X = ................................... mm

II. The actual length of the plant cell labelled Y in Image 3.1B is 70 μm (1 mm = 1000 μm).

Calculate the magnification of cell Y. Use your answer to (iii) I. to help you. Give your answer to two significant figures.

[2]

Magnification of cell Y in Image 3.1B = × ...................................

In Image 3.1B it can be clearly seen that similar cells are grouped together.

(i) State the name given to a group of similar cells.

[1]

(ii) Suggest one advantage to the organism of similar cells being grouped together.

[1]

The cell in Image 1.1 is adapted for one function.

Complete the following sentences by underlining the correct term in the brackets.

(i) Cells adapted for one function are called (special / specialised / specific).

(ii) Groups of similar cells are called (tissues / organs / organisms).

Complete the following table about the processes by which substances move through cell membranes.

Place a tick (✓) or a cross (×) in each box to indicate if the statement applies to each process or not.

The apparatus shown in Image 7.1 was set up using a piece of Visking tubing filled with sucrose solution. The Visking tubing was knotted at its bottom end and tied at its top end to a length of glass tube. The Visking tubing was then placed in a beaker of water and left for 1 hour. At the end of this time the sucrose solution had risen up the tube.

Image 7.1

Explain why the sucrose solution moved up the glass tube.

In an experiment on osmosis, students investigated the effect of different concentrations of glucose solution on cylinders of potato tissue. They used a 5 mm diameter cork borer to cut the cylinders. Each of the cylinders was then cut to a length of 40 mm. This is shown in Image 6.1.

Image 6.1

The students set up 5 test tubes A to E. Tube A contained 10 cm3 of distilled water whilst tubes B to E each contained 10 cm3 of glucose solution of different concentrations. A potato cylinder was placed in each of the test tubes and left for 2 hours. After this time the cylinders were removed and their final lengths were recorded. The contents of each tube and the results are shown in Table 6.2.

Table 6.2

Complete Table 6.2 by calculating the change in length of the potato cylinders.

Explain the change in length of the potato cylinder in Tube B.

(i) Use Table 6.2 to estimate the concentration of glucose solution which would cause no change of length of a potato cylinder.

[1]

Concentration = ................................... %

(ii) Describe how the students could improve their investigation to obtain a more accurate value for the concentration of glucose solution that would cause no change in the length of a potato cylinder.

[2]

Another group of students was asked by their teacher to test the reproducibility of the above experiment. State one other variable, the value of which they would need to know, before they could proceed.

The increasing importance of the commercial use of kelp has led scientists to conduct experiments in an attempt to grow them in land-based factories. In one experiment, sugar kelp (Laminaria saccharina) was grown in seawater in large vertical glass flasks. Scientists were trying to establish if the concentration of oxygen contained in the seawater affected the absorption of iodine by the kelp.

One set of results from the experiment is shown in the table.

(i) On the grid below, plot a line graph for the mass of iodine against the rate of oxygen flow. You must add suitable scales to each axis. Join the plots with a ruler.

[4]

(ii) Describe the effect of increasing the rate of flow of oxygen above 2.5 dm³ / minute on the mass of iodine extracted.

[1]

(iii) The kelp used in the 7 flasks were of different sizes but the experimental results could still be compared. Explain how this was possible.

[1]

(iv) For Flask 4 calculate how many times greater the concentration of iodine is in the kelp compared to the concentration of iodine in seawater. Give your answer in standard form.

Answer = ............................................... × greater

[2]

(v) The only source of iodine for kelp is the seawater in which they live. Explain how kelp is able to accumulate iodine against a concentration gradient.

[3]

Another group of scientists want to test the reproducibility of the above experiment. State one other controlled variable, the value of which they would need to know, before they could proceed.

The diagram shows a plant cell. Some structures have been labelled.

(i) Use a ruler to measure the length of the cell at X – Y in mm.

length at X – Y = ............................ mm

[1]

(ii) The diagram is magnified ×400.

Use your answer to part (i) to calculate the actual length of the cell.

actual length = ............................. mm

[1]

State the name of structure P.

.................................................

Complete the following table about plant cells.

This question is about enzymes.

Complete the following sentence by underlining the correct word.

Enzymes are made of carbohydrate / lipid / protein.

Graph 3.1 shows the effect of increasing pH on the rate of activity of an enzyme.

Graph 3.1

Use Graph 3.1 to describe how increasing pH affects enzyme activity.

Image 3.2 shows an enzyme, a denatured enzyme and a substrate molecule.

Image 3.2

(i) Describe what has happened to the active site in the denatured enzyme.

[1]

(ii) Enzymes react with substrates to produce products.

Explain why the denatured enzyme can no longer produce products.

[2]

State two variables that could denature an enzyme.

.......................................................... ..........................................................

A hen's egg is a single cell which is surrounded by a calcium carbonate shell.

Six hen's eggs were soaked in 4% ethanoic acid for 24 hours to dissolve their shells. After this time each egg is still intact as it is surrounded by a cell membrane. The initial masses of the 'naked eggs' (eggs without shells) were recorded.

The six 'naked eggs' were each placed in sucrose (sugar) solutions of different concentrations and left for 24 hours. After this time the final masses of the 'naked eggs' were recorded.

Complete the table above by calculating the % change in mass for egg number 6.

Space for working.

In the graph below the % change in mass of the 'naked eggs' is plotted against the concentration of sucrose solution.

(i) Complete the graph by adding the percentage change in mass for egg number 6.

[1]

(ii) From the graph state the concentration of sucrose solution where there was no net movement of water.

concentration of sucrose solution = .................. %

[1]

Explain the results for egg number 3 and egg number 5.

The photograph below shows a complete hen's egg on the right and one of the 'naked eggs', used in this experiment, on the left.

Suggest a concentration of sucrose solution in which this 'naked egg' was kept.

suggested concentration of sucrose solution = .......................... %

Rhys studies some plant tissue using the instrument shown below.

State the name of the instrument shown in the diagram.

The table shows the magnification of each of the four lenses.

Calculate the maximum magnification that is possible with this instrument.

maximum magnification = × .......................

Rhys places some of the plant tissue in water on a slide and lowers a cover slip on top as shown below.

He draws one cell from the tissue as seen under the maximum magnification. His drawing is shown below.

State what Rhys could have done to the plant tissue to show more detail of the cell structures.

State the function of the nucleus.

Scientists investigated absorption of three different sugars in a sample of healthy small intestine in the laboratory. They analysed the absorption of the sugars in the presence or absence of cyanide. Cyanide is a chemical that prevents respiration taking place in cells.

The results are shown in Table 5.2.

Table 5.2

Use the information in Table 5.2 to answer the following questions.

(i) State which sugar is absorbed by active transport. Explain your answer.

[4]

(ii) One of the scientists stated that all three of the sugars in the investigation could be absorbed by diffusion. Explain how the evidence in Table 5.2 supports this conclusion.

[2]

State the meaning of the term diffusion.

After a lesson on the properties of cell membranes a year 10 class was asked to investigate some of these properties using Visking tubing. They were given the following instructions:

• Soak a 15 cm length of Visking tubing in water to soften it.

• Tie a knot in one end of the tube.

• Fill the tube with a solution made up of protein and glucose dissolved in water.

• Tie a knot in the open end of the tube.

• Wash the tube under a stream of tap water for 15 seconds.

• Using a glass rod, suspend the Visking tubing in a beaker of distilled water.

The diagram below shows how your apparatus should appear.

(i) Why were the students instructed to 'wash the tube under a stream of tap water for 15 seconds'?

[1]

The students were asked to sample the distilled water in the beaker for the presence of both glucose and protein at the start of the experiment and every minute for the next four minutes.

Dafydd decided to photograph his results on his smart phone. The photographs he obtained are shown below.

(ii) Explain Dafydd's results, at four minutes, for the contents of the beaker for both the Benedict's test and the Biuret test.

Benedict's test

[3]

Biuret test

[3]

The photograph shows one labelled blood cell from the circulatory system.

(i) Complete the table by stating the name and function of structures A and B.

[4]

(ii) The cell contains many mitochondria. State the function of mitochondria.

[1]

Complete the table below by using words from the list to identify an organ, and a cell from the human circulatory system.

The diagram below shows a red blood cell.

(i)

I. Complete the following calculation.

diameter of red blood cell = 8.0 µm

radius (r) = 4.0 µm

Radius² = ....................................... µm²

[1]

II. Use your answer to part I. and the formula 3.14 × radius², to calculate the surface area of one side of a red blood cell to the nearest whole number.

Surface area of one side of red blood cell = .................... µm²

[1]

(ii) Red blood cells have a large surface area.

State the function of red blood cells and suggest how a large surface area helps red blood cells to be more efficient.

[2]

(iii) Red blood cells are specialised cells.

Give the meaning of the term specialised cell.

[1]

Sarah was viewing a smear of blood under a light microscope. How could she calculate the magnification of the microscope she was using?

Visking tubing has small pores (holes) in its membrane. Students investigated the movement of molecules through membranes using Visking tubing.

The students set up the apparatus shown below.

They took samples of water from the beaker at the start and at 15 minutes.

They tested the samples for the presence of glucose using Benedict's reagent.

The results are shown in the table.

From the table:

(i) State the conclusion that can be made from the Benedict's test observation at the start.

[1]

(ii) Explain the observations at 15 minutes for the Benedict's test.

[2]

During the investigation, a number of processes occurred.

Use the information opposite to complete the following table by writing true or false against each statement. One has been done for you.

[3]

Carbohydrase is the enzyme that digests the starch in pasta into simple sugars. Protease is an enzyme that digests protein.

With reference to the diagrams, suggest how each of the enzyme molecules are different and state why it is important that the chains of amino acids are folded.

Complete the following sentences about enzymes using some of the words from the list below.

Some enzymes break down large molecules into small molecules, for example during ......................................................................... and ......................................................................... .

Other enzymes build up large molecules from small molecules, for example during ......................................................................... .

Many different types of molecules pass across cell membranes.

Complete the table below to show the direction of movement of molecules between blood and muscles. Place one tick (✓) in each row.

Describe the method you would use to make a slide of your own cheek cells using the apparatus below.

Make a large drawing of one cheek cell in the box below.

Include the cell structures you would see when viewed at the highest magnification of a light microscope. No labels are required.

Rhys was asked by his teacher to set up a light microscope so that he could view some cells at a magnification of ×100. The microscope had three objective lenses of ×4, ×10 and ×40 magnifications. Rhys was also given a prepared slide of muscle cells.

Explain how Rhys could view the muscle cells at a magnification of ×100.

State the function of structure A on the diagram.

When Rhys viewed the muscle cell under the microscope he could see that the cells were not found on their own, but were grouped together in large numbers.

(i) Muscle cells are described as being specialised cells. State the advantage to the organism of having specialised cells.

[1]

(ii) State the name given to a large number of the same cells grouped together.

.............................................................................................................

[1]

In biology, what is meant by the term organ?

Use some of the following words to complete the table about enzymes.

The diagram shows four enzymes A – D and four substrates 1 – 4.

[Figure: Diagram showing four enzymes (A, B, C, D) each with a differently-shaped active site, and four substrate molecules (1, 2, 3, 4) each with a differently-shaped matching region, illustrating the lock and key theory]

Use your knowledge of the lock and key theory to complete the table below by matching each enzyme to its substrate.

The graph shows the effect of temperature on the rate of an enzyme controlled reaction between 10 °C and 50 °C.

(i) From the graph, describe the effect of temperature on the rate of the reaction between 10 °C and 50 °C.

[3]

(ii) Most enzymes are denatured by boiling.

Use your answer to part (b) to help explain why a denatured enzyme can no longer work.

[2]

Visking tubing acts as a model of absorption in the digestive system.

The diagram shows a Visking tubing bag filled with a solution of starch and glucose, in a beaker of water.

Samples from inside the Visking tubing bag and the water in the beaker were tested for starch and glucose at the start. This was repeated after 10 and 20 minutes.

(i) Complete the table below by writing a ✓ or ✗ in each space to show the expected results at 20 minutes.

key: ✓ molecule present; ✗ molecule absent

[3]

(ii) Use your knowledge of the size of starch and glucose molecules to explain the expected results at 20 minutes for the water in the beaker.

[2]