Microscopy

The pathogen Vibrio cholerae causes the disease cholera.

Figure 7 shows Vibrio cholerae bacteria.

Complete the table to show the function of structure P and structure Q.

On the original image, the length of one bacterial cell is 12 mm.

The actual length of this bacterial cell is 2.0 µ m.

Calculate the magnification.

State one symptom of the disease caused by Vibrio cholerae.

State how the disease caused by Vibrio cholerae is transmitted.

Describe the specific immune response when a pathogen infects the body.

Figure 9 shows a stoma on the lower epidermis of a leaf as seen using a

Draw the stoma and two cells around it in the box.

Give the name of the two cells around the stoma.

A student observed that a plant in a room had grown towards the light.

Name the plant hormone that causes the plant to grow towards the light.

Name the type of tropism that causes the plant to grow towards the light.

Figure 10 compares the root hair cells of two plants.

Plant A is adapted to growing in wet soil.

Plant B is adapted to growing in dry soil.

Compare the root hair cells of Plant A with the root hair cells of plant B.

Figure 11 shows sections of a leaf from plant A and a leaf from plant B.

plant A (wet soil)
plant B (dry soil)

Figure 11

State two differences in the leaf structure shown in Figure 11 that help plant B to survive in a dry environment.

Figure 22 shows a type of bacteria (Lactobacillus acidophilus) that is found in cow’s milk.

The magnification of this image is ×18 000.

Measure the length of the bacterium labelled A.

Use your measurement to calculate the actual length of this bacterium in millimetres.

Give your answer in standard form.

Figure 23 shows the growth rate of two species of bacteria at different pH values.

State a pH that allows the growth of both Lactobacillus acidophilus and Staphylococcus aureus.

Describe the relationship between pH and the growth of Staphylococcus aureus, as shown in Figure 23.

A student investigated the effect of temperature on the decay of milk.

Milk was placed in a beaker in a water bath at 5 °C for 72 hours.

The pH of the milk was measured every 24 hours using a pH probe.

The investigation was repeated at different temperatures.

Figure 24 shows the results of this investigation.

Which is a variable that the student needs to control in this investigation?

Describe the changes in the pH of the milk at 30 °C from 0 hours to 72 hours, as shown in Figure 24.

Calculate the rate of decay of the milk at 20 °C for the 72 hours of this investigation.

Use the equation:

_........ change in pH per hour

Figure 7 shows a type of bacteria (Lactobacillus acidophilus) that is found in cow’s milk.

The magnification of this image is ×18 000.

Measure the length of the bacterium labelled A.

Use your measurement to calculate the actual length of this bacterium in millimetres.

Give your answer in standard form.

Figure 8 shows the growth rate of two species of bacteria at different pH values.

State a pH that allows the growth of both Lactobacillus acidophilus and S taphylococcus aureus.

Describe the relationship between pH and the growth of Staphylococcus aureus, as shown in Figure 8.

A student investigated the effect of temperature on the decay of milk.

Milk was placed in a beaker in a water bath at 5 °C for 72 hours.

The pH of the milk was measured every 24 hours using a pH probe.

The investigation was repeated at different temperatures.

Figure 9 shows the results of this investigation.

Which is a variable that the student needs to control in this investigation?

Describe the changes in the pH of the milk at 30 °C from 0 hours to 72 hours, as shown in Figure 9.

Calculate the rate of decay of the milk at 20 °C for the 72 hours of this investigation.

Use the equation:

_........ change in pH per hour

Figure 12 shows the lower epidermis of a leaf, with a stoma labelled.

(Source: © Quagga Media/Alamy Stock Photo)

Figure 12

State the number of guard cells shown in Figure 12.

State one gas that leaves the stomata and one gas that enters the stomata during daylight.

gas leaving stomata

gas entering stomata

State why the stomata close.

A student wanted to view the cross-section of a leaf on a prepared slide.

Describe how a light microscope would be used to observe this slide.

Sugars are transported from the leaves to the rest of the plant.

Explain how sugars are moved through the plant.

A student made a microscope slide of cells taken from the inside of their mouth.

The student wore gloves while using a swab to collect cells from their mouth.

Give one other safety precaution the student should take.

A light microscope was used to obtain an image similar to the one shown in Figure 6.

(Source: © STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY)

Figure 6

Describe how the student used the light microscope to view these cells at a magnification of 400.

The cytoplasm of a cell contains a nucleus.

Explain the role of one other structure in the cytoplasm of a human cell.

DNA can be extracted from human cells in a similar way to the method used to extract DNA from fruits.

Describe the stages of the method used to extract DNA from cells.

The Human Genome Project sequenced the order of the bases in the human genome.

Give two other outcomes from the Human Genome Project.

Figure 7 shows images of two stone tools.

Scientists think that tool A was probably used by Homo erectus around 1.6 million years ago.

Tool B was probably used by Homo habilis around 2 million years ago.

Give one reason, using Figure 7, why scientists think that tool A was used by a more recent human ancestor.

Describe how scientists can date stone tools using information from where the tools were discovered.

Differences in fossilised bones indicate structural changes that have occurred during the evolution of humans.

Describe two structural changes that have occurred during human evolution.

The migration patterns of humans can be tracked by analysing DNA in mitochondria.

Figure 8 shows a mitochondrion viewed using an electron microscope.

At a magnification of 62 000 this mitochondrion has a length of 434 mm.

Calculate the actual length of this mitochondrion.

Give your answer in micrometres (µ m).

Explain why an electron microscope is used to see mitochondria clearly.

Scientists use microscopes to study cells.

Figure 1 shows a light microscope.

Draw one straight line from each part of the microscope to its function.

Figure 2 shows two photographs of bacteria.

Photograph A was taken through a light microscope.

Photograph B was taken using an electron microscope.

Draw, in the box, the bacterial cell labelled X.

Label one part of the bacterial cell on your diagram.

State one advantage of using a light microscope and one advantage of using an electron microscope to study these bacterial cells.

A light microscope_........

An electron microscope_........

Figure 1 shows an animal cell.

Which part of the cell is labelled Y?

Which structures are found in the part labelled Z?

Name the part of an animal cell where respiration occurs.

A microscope can be used to observe the structure of a cell.

Figure 2 shows a microscope.

Give one advantage of using a microscope to look at cells.

Draw one straight line from each part of the microscope to its function.

Figure 3 shows some of the units used when cells and organelles are measured.

Give the name of the smallest unit shown in Figure 3.

Figure 17 shows colonies of bacteria growing on an agar plate.

Each colony starts as one bacterium.

Every time bacteria reproduce, the number of bacteria in each colony doubles.

Calculate the number of bacteria in a colony after five hours, if each bacterium reproduces every 30 minutes.

Some bacteria are pathogens.

State the meaning of the term pathogen.

Explain why antibiotics can be used to treat bacterial infections.

A rod-shaped bacterium is 0.005 mm long.

A student draws the rod-shaped bacterium.

The bacterium in the drawing is 80 mm long.

Calculate the magnification of this drawing.

* (c) Figure 18 shows a bacterial cell and a plant cell.

Describe the similarities and differences of a bacterial cell and a plant cell.

Figure 4 shows colonies of bacteria growing on an agar plate.

Each colony starts as one bacterium.

Every time bacteria reproduce, the number of bacteria in each colony doubles.

Calculate the number of bacteria in a colony after five hours, if each bacterium reproduces every 30 minutes.

Some bacteria are pathogens.

State the meaning of the term pathogen.

Explain why antibiotics can be used to treat bacterial infections.

A rod-shaped bacterium is 0.005 mm long.

A student draws the rod-shaped bacterium.

The bacterium in the drawing is 80 mm long.

Calculate the magnification of this drawing.

Figure 16 shows a photomicrograph of two stomata in a leaf.

The length of one guard cell in this image is 6 mm.

Convert the length of this guard cell into micrometres (µ m).

The image has been magnified 150×.

Calculate the actual size of the guard cell.

Give your answer in standard form in mm.

Explain the role of denitrifying bacteria in the nitrogen cycle.

*(c) Describe how carbon is cycled through the biotic and abiotic components of an ecosystem.

A student was investigating mitosis in the roots of a garlic plant.

Describe how the student could prepare a microscope slide to show mitosis in the growing roots of a garlic plant.

Describe what is produced when a single cell divides by mitosis.

The student observed 89 cells on the microscope slide.

Figure 6 shows the number of cells at each stage of the cell cycle.

Use this equation to calculate the mitotic index for this slide.

Give your answer to three significant figures.

The mitotic index is often used in the diagnosis of cancer.

State the effect of cancer on cell division.

2 (a) Blood contains red blood cells, white blood cells, plasma and platelets.

(i) Draw one straight line from each part of the blood to its function.

part of the blood function

Figure 2 shows some red blood cells.

(Source: © SciePro/Shutterstock)

Figure 2

(ii) State two features that can be seen in the red blood cells in Figure 2.

(b) Lymphocytes are white blood cells that produce large amounts of protein.

(i) Which organelle is needed to produce large amounts of protein?

A small lymphocyte has a diameter of 10 µ m (micrometres). A microscope magnifies this lymphocyte 400 times.

(ii) Calculate the diameter of the image of the lymphocyte seen using this microscope.

image size_{..............................................................}

(iii) How many micrometres are in 1 mm (millimetre)?

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.

2 Figure 3 shows a cell from an onion root tip. This cell is dividing by mitosis.

(a) (i) Which structure is labelled Z?

(ii) Mitosis produces new cells. Give two reasons why mitosis is important in living things.

(iii) Draw one straight line from each stage of the cell cycle to its description.

stage of cell cycle description

(b) A student is preparing a microscope slide of plant cells.

(i) State what can be added to the slide to make the plant cells more visible.

(ii) The microscope has two lenses:

• an eyepiece lens with 10 magnification

• an objective lens with 40 magnification

Which is the total magnification of this microscope?

(c) Name one part of a light microscope that can be moved to obtain a clear image of plant cells.

5 (a) Figure 7 shows cells from an onion root tip as seen using a light microscope.

(Source: © Rattiya Thongdumhyu/Shutterstock)

Figure 7

(i) Identify the stages of mitosis shown in cell Q and cell R.

(ii) Describe two processes that occur in cells during prophase.

(iii) State the term used to describe the process which occurs after mitosis, when the cell divides into two.

(iv) The diameter of one cell in Figure 7 is 0.075 mm. Which is this diameter in µm?

(b) A student placed a prepared slide on the stage of a light microscope. Describe how to adjust the microscope to view the slide at a magnification of ×400.

(c) Arthritis is a condition that occurs when cells in joints get damaged or destroyed. Stem cell therapy can be used to treat arthritis. Discuss the benefits and risks of using stem cell therapy to treat arthritis.

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 1 shows human blood seen using a light microscope.

The organelle labelled X controls the activities of the white blood cell.

What is the name of organelle X?

Use words from the box to complete the sentences.

Red blood cells contain the substance_........ .

Blood plasma is a_........ .

Describe two ways that white blood cells protect the body from disease.

Figure 2 shows a white blood cell on a 100 µ m scale.

State the width of the white blood cell.

Figure 1 shows human blood seen using a light microscope.

Explain why using an electron microscope shows the structures in the white blood cells more clearly.

Figure 12 shows how the leaves are arranged on a plant.

Which reason explains why the leaves are arranged in this way?

Figure 13 shows guard cells and stomata on the lower surface of a leaf.

(Source: © Rattiya Thongdumhyu/Shutterstock)

Figure 13

Measure the length of the line on the labelled guard cell in mm.

The actual length of the labelled guard cell is 0.05 mm.

Calculate the magnification of this image.

Figure 14 shows the number of stomata per mm² on the lower surface of leaves from plants growing in soils with different water content.

Explain the difference in the number of stomata per mm² on the leaves of the plants grown in dry and wet soils.

*(d) Figure 15a shows a plant that has been placed on its side.

Figure 15b shows the same plant after 5 days.

Explain why the growth of the plant has changed.

Figure 18 shows ciliated epithelial cells from the airways of a human as seen using a light microscope.

Draw the cell labelled A in the box below.

Label three parts of this cell on your diagram.

State the function of the ciliated epithelial cells in the airways of the human breathing system.

Figure 19 shows equipment used to investigate the rate of respiration in maggots.

As the maggots respire, the drop of coloured liquid moves towards the test tube.

Figure 20 shows the position of the drop of coloured liquid after ten minutes.

Use information from Figures 19 and 20 to calculate the mean rate of respiration of the maggots in mm per minute.

*(c) Explain how alveoli in human lungs are adapted for gas exchange.

Include the names of the gases that are being exchanged.

Figure 4 shows ciliated epithelial cells from the airways of a human as seen using a light microscope.

Draw the cell labelled A in the box below.

Label three parts of this cell on your diagram.

State the function of the ciliated epithelial cells in the airways of the human breathing system.

Figure 5 shows equipment used to investigate the rate of respiration in maggots.

As the maggots respire, the drop of coloured liquid moves towards the test tube.

Figure 6 shows the position of the drop of coloured liquid after ten minutes.

Use information from Figures 5 and 6 to calculate the mean rate of respiration of the maggots in mm per minute.

Describe a control for this investigation.

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 4 shows three cells.

What is structure X ?

The bacterial cell in Figure 4 has a flagellum.

State the function of a flagellum.

Give one other difference between the bacterial cell and the animal cell shown in Figure 4.

Substances move into and out of cells.

How does oxygen move into and out of cells?

A plant leaf cell is 0.04 mm long.

Calculate the length of the image after this cell has been magnified 500 times.

Figure 14 shows a banana plantation.

After the bananas have been harvested, the old plants are cut down.

The suckers then develop into mature plants producing the next crop of bananas.

The tip of each sucker contains a group of cells called a meristem.

Describe the function of a meristem in the growth of a plant.

A student took a sample of cells from a meristem to view under a light microscope.

Describe how the student would prepare a microscope slide using these cells.

Figure 15 is a drawing of a eukaryotic cell.

Structure Z is found in plant leaf cells.

Name structure Z.

Give one function of the mitochondrion.

*(c) DNA is found in the nucleus of cells.

Describe the structure of DNA and how it can be extracted from plant cells.

Figure 2 shows a banana plantation.

After the bananas have been harvested, the old plants are cut down.

The suckers then develop into mature plants producing the next crop of bananas.

The tip of each sucker contains a group of cells called a meristem.

Describe the function of a meristem in the growth of a plant.

A student took a sample of cells from a meristem to view under a light microscope.

Describe how the student would prepare a microscope slide using these cells.

Figure 3 is a drawing of a eukaryotic cell.

Structure Z is found in plant leaf cells.

Name structure Z.

Give one function of the mitochondrion.

Describe how a prokaryotic cell is different from the cell in Figure 3.

Bacteria grown in a liquid medium is called a bacterial culture. As the number of bacteria increases the bacterial culture becomes opaque. This is because light is absorbed by the bacterial culture.

To measure the increase in the number of bacteria, a scientist took a sample from the culture every 20 minutes.

The apparatus shown in Figure 7 detects the amount of light transmitted through the bacterial sample and uses it to calculate the amount of light absorbed.

Give two aseptic techniques the scientist should use when taking samples from the bacterial culture.

Figure 8 shows the amount of light absorbed by the bacterial sample.

The bacterial population increases rapidly between 40 and 100 minutes.

Calculate the time taken for the amount of light being absorbed by the bacterial sample to double from 0.5 to 1.0 arbitrary units.

The scientist put a small sample of the bacteria on a microscope slide and used a magnification of ×1000 to view the sample.

The bacteria could not be seen very clearly.

Give one improvement the scientist could make to view the bacteria more clearly.

Some bacteria contain a gene that produces a toxin that can kill insects.

This gene can be inserted into the genome of a crop plant.

What method is used to insert the gene from the bacteria into the crop plant?

*(ii) Discuss the advantages and disadvantages of growing crop plants that produce a toxin that can kill insects.

A student investigated mitosis in the root tip of a garlic plant.

Explain why the student used the tip of the root.

The student squashed the root tip on a microscope slide to spread out the cells.

The slide was placed on the stage of a microscope.

Describe how to use the microscope to obtain a clear image of the cells.

The student could not see the chromosomes inside the cells.

State what can be added to the root tip squash to make the chromosomes visible.

Figure 2 shows a root cell in a stage of mitosis.

Which stage of mitosis is shown in Figure 2?

Describe what is happening in Figure 2.

Organisms can be classified by the five kingdom or three domain method.

What is the name of the domain that plants belong to?

Plant cells contain chloroplasts.

What happens in a chloroplast?

Give a reason why the three domain method of classification has been suggested.

Figure 7 shows a cyanobacterium magnified 50 000 times.

The line AB shows the diameter of the bacterial cell.

(Source: © The Christian Science Monitor)

Figure 7

Calculate the actual diameter of the cyanobacterium.

Give your answer in micrometres (µ m).

Bacterial cells contain plasmids.

Describe three other features of a bacterial cell.

Figure 8 shows a plasmid containing the human insulin gene.

Explain how the human insulin gene can be inserted into a plasmid.

(a) Photosynthesis occurs in leaves.

Which substance is needed for photosynthesis?

A leaf cell is 0.08 mm long.

Calculate the length of the image of this cell after it has been magnified 50 times using a microscope.

Pine trees can live in dry soil.

Use words from the box to complete the sentences.

The pine leaf has stomata in pits to reduce the loss of_........ .

The pine leaf is needle-shaped to reduce the surface_........ .

Figure 5 shows young tomato plants growing in a glasshouse.

The young tomato plants are growing towards the light.

Explain how a plant hormone causes these shoots to grow towards the light.

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.

A student cut a piece of onion and placed it on a microscope slide.

The student then placed this slide on the stage of a light microscope and looked through the eyepiece.

No cells could be seen in the piece of onion.

Explain two ways this method could be improved to see details of the onion cells.

Figure 7 shows mitosis occurring in some plant cells.

The cells in Figure 7 were taken from a rapidly growing part of a plant.

Which part of a plant has rapidly dividing cells?

Which stage of mitosis is shown in cell R?

Describe two genetic similarities of the new cells that would be produced by cell Q in Figure 7.

The cells in Figure 7 were heated in hydrochloric acid.

State two safety precautions that should be taken when heating hydrochloric acid.

Explain one advantage of using an electron microscope to observe plant cells.

In 2012, two scientists were awarded the Nobel prize for their research on stem cells.

They showed that adult cells could be reprogrammed to become cells with the properties of embryonic stem cells.

Describe the possible benefits of this research.

Figure 11 shows four stages of mitosis, labelled P, Q, R and S.

Which is the correct order for these stages?

The stage of mitosis labelled S in figure 11 is

Interphase is part of the cell cycle.

Describe what happens during interphase.

Figure 12 shows a root tip with cells in different stages of mitosis.

The image was magnified 400 ×.

Explain how a magnification of 400 × can be obtained using the lenses on a light microscope.

(a) Figure 19 shows a diagram of a red blood cell from a turtle and a diagram of a red blood cell from a human.

These cells are animal cells.

Animal cells do not have

The actual length of the red blood cell from a turtle is 20.5 μ m.

Calculate the length of the magnified image of the red blood cell of the turtle when magnified 400 ×.

The width of the human red blood cell, when magnified 400 ×, is 3.08 mm.

Calculate the actual width of the cell and show your answer in standard form.

Red blood cells are carried in veins and arteries.

Figure 20 shows the equipment used to measure the elasticity of an artery.

Describe a method you could use to see how much the ring of tissue from an artery could stretch before it no longer returned to its original size.

Give one safety precaution you need to take when handling animal tissue such as blood vessels.

Figure 21 shows the circulatory system of a frog.

Explain why the circulatory system of a frog is less efficient at carrying oxygen to the tissues than the circulatory system of a human.

State why a coverslip is placed on top of the leaf peel.

Explain why the leaf peel rather than the whole leaf was viewed with a microscope.

The student drew a biological diagram of the leaf peel taken from the underside of the leaf.

Figure 23 shows this diagram.

State the number of stomata visible on Figure 23.

The student observed that the stomata were open.

Describe how stomata open.

*(c) Figure 24 shows xylem and phloem. Xylem and phloem are involved in the transport of substances through a plant.

Use Figure 24 to help you describe how water and sucrose move through a plant.

(a) Figure 3 shows a diagram of a red blood cell from a turtle and a diagram of a red blood cell from a human.

These cells are animal cells.

Animal cells do not have

The actual length of the red blood cell from a turtle is 20.5 μ m.

Calculate the length of the magnified image of the red blood cell of the turtle when magnified 400 ×.

The width of the human red blood cell, when magnified 400 ×, is 3.08 mm.

Calculate the actual width of the cell and show your answer in standard form.

Red blood cells are carried in veins and arteries.

Figure 4 shows the equipment used to measure the elasticity of an artery.

Describe a method you could use to see how much the ring of tissue from an artery could stretch before it no longer returned to its original size.

Give one safety precaution you need to take when handling animal tissue such as blood vessels.

A student compared the number of stomata on the upper and lower surfaces of a leaf.

She completed a leaf peel as shown in Figure 5.

leaf coated with clear layer of nail varnish layer of nail varnish placed nail varnish
removed on a microscope slide

Figure 5

The layer of nail varnish shows an impression of the cells on the surface of the leaf.

State why a coverslip is placed on top of the leaf peel.

Explain why the leaf peel rather than the whole leaf was viewed with a microscope.

The student drew a biological diagram of the leaf peel taken from the underside of the leaf.

Figure 6 shows this diagram.

State the number of stomata visible on Figure 6.

The student observed that the stomata were open.

Describe how stomata open.

The leaf peel from the upper surface of this leaf showed no stomata.

Explain why it is an advantage to the plant to have this distribution of stomata in the upper and lower surfaces of the leaf.