Microscopy

Figure 8 shows the lower epidermis of a leaf, with a stoma labelled.

(Source: © Quagga Media/Alamy Stock Photo)

Figure 8

State the number of guard cells shown in Figure 8.

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 3.

(Source: © STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY)

Figure 3

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 4 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 4, 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 5 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).

_........ µm

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 10 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.

_........ bacteria

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.

magnification =_........

* (c) Figure 11 shows a bacterial cell and a plant cell.

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

Figure 2 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.

_........ bacteria

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.

magnification =_........

Figure 9 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.

_........ 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 4 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.

Mitotic index_........

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

State the effect of cancer on cell division.

Figure 3 shows some onion cells that have been soaked in a concentrated salt solution.

(Source: © Rattiya Thongdumhyu/Shutterstock)

Figure 3

The cells in Figure 3 have been stained.

Give one reason why the cells have been stained.

Which is the name of the structure labelled V?

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.

Figure 4 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.

A student investigated the percentage change in mass of potato cylinders placed in sucrose solutions of different concentrations.

Figure 5 shows the results of the student’s investigation.

concentration of sucrose solution in mol/dm³

Figure 5

State two conclusions that can be made from these results.

Figure 1 shows a cell from an onion root tip.

This cell is dividing by mitosis.

Which structure is labelled Z?

Mitosis produces new cells.

Give two reasons why mitosis is important in living things.

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

A student is preparing a microscope slide of plant cells.

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

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?

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

Figure 4 shows cells from an onion root tip as seen using a light microscope.

(Source: © Rattiya Thongdumhyu/Shutterstock)

Figure 4

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

Describe two processes that occur in cells during prophase.

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

The diameter of one cell in Figure 4 is 0.075 mm.

Which is this diameter in µm?

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.

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.

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.

_........ µm

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 11 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 12 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 13 shows the position of the drop of coloured liquid after ten minutes.

Use information from Figures 12 and 13 to calculate the mean rate of respiration of the maggots in mm per minute.

_........ 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 3 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 4 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 5 shows the position of the drop of coloured liquid after ten minutes.

Use information from Figures 4 and 5 to calculate the mean rate of respiration of the maggots in mm per minute.

_........ mm per minute

Describe a control for this investigation.

Figure 8 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 9 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.

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 1 shows a root cell in a stage of mitosis.

Which stage of mitosis is shown in Figure 1?

Describe what is happening in Figure 1.

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 2 shows a cyanobacterium magnified 50 000 times.

The line AB shows the diameter of the bacterial cell.

(Source: © The Christian Science Monitor)

Figure 2

Calculate the actual diameter of the cyanobacterium.

Give your answer in micrometres (µ m).

_........ µm

Bacterial cells contain plasmids.

Describe three other features of a bacterial cell.

Figure 3 shows a plasmid containing the human insulin gene.

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

Figure 7 shows a plant cell as seen under a light microscope.

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

Figure 7

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 8.

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 4 shows mitosis occurring in some plant cells.

The cells in Figure 4 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 4.

The cells in Figure 4 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 8 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 8 is

Interphase is part of the cell cycle.

Describe what happens during interphase.

Figure 9 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 9 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 ×.

_........ μm

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.

_........ mm

Red blood cells are carried in veins and arteries.

Figure 10 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 11 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 13 shows this diagram.

State the number of stomata visible on Figure 13.

The student observed that the stomata were open.

Describe how stomata open.

*(c) Figure 14 shows xylem and phloem. Xylem and phloem are involved in the transport of substances through a plant.

Use Figure 14 to help you describe how water and sucrose move through a plant.

(a) Figure 1 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 ×.

_........ μm

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.

_........ mm

Red blood cells are carried in veins and arteries.

Figure 2 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.

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 4 shows this diagram.

State the number of stomata visible on Figure 4.

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.