Units and scale in cells

Figure 2 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 3 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.

The pathogen Vibrio cholerae causes the disease cholera.

Figure 5 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 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.

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 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 =_........

Gas exchange happens in the alveoli in the lungs.

Figure 7 shows an alveolus and a capillary.

(adapted from: sciencepics/shutterstock)

Figure 7

Name the gas used in respiration that moves from the alveolus into the capillary.

Name the gas produced by respiration that moves from the capillary into the alveolus.

The capillary wall is only one cell thick.

Explain how gases move from the alveolus to the capillary.

Explain the advantages of red blood cells passing one at a time through this narrow capillary.

The average number of alveoli in each human lung is 280 million.

The surface area of 1 million alveoli is 0.25 m².

Calculate the total surface area of a human lung.

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.

Blood contains red blood cells, white blood cells, plasma and platelets.

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

Figure 2 shows some red blood cells.

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

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

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.

Calculate the diameter of the image of the lymphocyte seen using this microscope.

image size_........ µm

How many micrometres are in 1 mm (millimetre)?

Figure 4 shows a cross-section of a root nodule on a leguminous plant.

Bacteria in the root nodule provide the leguminous plant with nitrogen compounds.

The leguminous plant provides the bacteria with sugars.

(Source: © Nigel Downer / Science Photo Library)

Figure 4

Which term describes the relationship between this leguminous plant and the bacteria?

The width of this root nodule is 7.5 mm.

Give the width in µ m.

Figure 5 shows part of the nitrogen cycle.

Identify the types of microorganism involved in process X and process Y.

Explain how crop rotation increases nitrate levels in the soil.

Explain why increased nitrate levels in the soil improve crop yield.

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 9 shows a sperm cell.

Describe how structure A and structure B enable fertilisation.

structure A

structure B

Figure 10 shows a human egg cell, magnified ×700.

(Source: © Pascal Goetgheluck / Science Photo Library)

Figure 10

Calculate the actual width of the region indicated by the line on Figure 10.

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 11 shows the results.

Evaluate the results of this investigation.

You should include calculations using the data in Figure 11.

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 6 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 6

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

Give your answer in mm.

_........ 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 1 shows three cells.

What is structure X ?

The bacterial cell in Figure 1 has a flagellum.

State the function of a flagellum.

Give one other difference between the bacterial cell and the animal cell shown in Figure 1.

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.

length of image =_........ mm

James Watson and Francis Crick built a model that showed that DNA has a double helix structure.

Which statement about DNA is correct?

Figure 6 shows the percentage of each base in human DNA.

Describe how this data provides evidence for base pairing in DNA.

A scientist obtained a mass of 0.0062 nanograms of DNA from a diploid human cell.

Calculate the mass of DNA the scientist should obtain from a haploid human cell.

Give your answer in picograms.

(1 nanogram = 1000 picograms)

_........ picograms

A student used the method shown in Figure 7 to compare the mass of DNA extracted from strawberry fruit cells and from kiwi fruit cells.

State why ethanol is used.

State two variables the student needs to control when using this method to compare the mass of DNA from these two fruits.

The student repeated the experiment.

Give one reason why.

Mitosis and meiosis are processes that produce new cells.

Compare the outcomes of mitosis and meiosis.

A scientist obtained a mass of 0.0062 nanograms of DNA from a diploid human cell.

Calculate the mass of DNA the scientist should obtain from a haploid human cell.

Give your answer in picograms.

(1 nanogram = 1000 picograms)

_........ picograms

A student used the method shown in Figure 1 to compare the mass of DNA extracted from strawberry fruit cells and from kiwi fruit cells.

State why ethanol is used.

State two variables the student needs to control when using this method to compare the mass of DNA from these two fruits.

The student repeated the experiment.

Give one reason why.

Mitosis and meiosis are processes that produce new cells.

Compare the outcomes of mitosis and meiosis.

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 8 shows the number of neurones in the brain of different animals.

Calculate the difference between the number of neurones in the brain of the rat and the brain of the frog.

Give your answer in standard form.

_........ neurones

Most neurones in the brain are unmyelinated whereas motor neurones are myelinated.

Explain why myelination is needed on motor neurones but not on neurones in the brain.

Figure 9 shows a sensory neurone.

Label the axon on Figure 9.

Describe the role of sensory neurones.

Explain how impulses are transmitted at synapses.

(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.

(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.