AQA AS Biology

Topic Questions

2.2 The Microscope in Cell Studies

1a4 marks

Table 1 compares some of the features of optical and electron microscopes. 

Table 1

 

Optical microscope

Electron microscope

Image is formed using...

Light

A

Resolution

Low

B

Maximum useful magnification

C

x 1,500,000

Can be used to observe...

Cells down to the level of mitochondria and chloroplasts.

D

Use your knowledge of microscopes to fill the gaps labelled A-D in Table 1.

1b2 marks

Describe how a transmission electron microscope uses electrons to generate an image.

1c2 marks

Give one advantage and one disadvantage of using a transmission electron microscope. 

1d1 mark

Figure 1 below shows an image of algae taken using an electron microscope.

Figure 1

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Image courtesy of SecretDisc.. Licensed under Creative Commons Attribution-Share Alike 3.0 Unported License.  Reused and distributed under conditions found at: https://creativecommons.org/licenses/by-sa/3.0/deed.en

State whether the image in Figure 1 was taken using a transmission electron microscope or a scanning electron microscope.

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2a2 marks

A student used an optical microscope to view a specimen. They wanted to work out the actual size of the specimen, and decided to use a stage micrometer together with the ruler visible inside the eyepiece of the microscope (known as the eyepiece graticule).

State why a stage micrometer is needed as well as the eyepiece graticule.

2b2 marks

Figure 1 shows an image of a cell taken using a different type of microscope to that used by the student in part a).

Figure 1

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Identify the type of cell shown in Figure 1 and give one cell feature that helped you reach this conclusion.

2c2 marks

State which type of microscope was used to take the image shown in Figure 1. Give one reason for your answer. 

2d2 marks

The student decided to produce a biological drawing of Figure 1. Give two conventions that the student must be sure to follow for their diagram to be classed as a biological drawing.

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3a1 mark

Figure 1 shows an image of a chloroplast taken under a microscope. 

Figure 1

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Name the part of a chloroplast labelled X in Figure 1

3b2 marks

The chloroplast shown in Figure 1 contains starch grains. State and explain the function of starch in plant cells.

3c1 mark

A student wanted to view starch grains under an optical microscope, and their teacher told them to use a stain in order to do this. State why the student would need to use a stain to view starch grains.

3d3 marks

Describe the procedure that the student would need to follow to prepare a plant cell slide for viewing starch grains under an optical microscope. 

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4a1 mark

Figure 1 below shows a cross section of a leaf taken using an optical microscope with a magnification of x250. 

Figure 1

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Use the information provided to calculate the actual length of a palisade cell, as marked by line A on Figure 1. Give your answer in μm.  

4b2 marks

State the function of a palisade cell, and use detail shown in Figure 1 to explain how it is specialised for this function.

4c2 marks

Figure 1 shows some cell organelles inside the cells of the leaf, but it doesn’t show structures such as ribosomes or cell membranes. Use your knowledge of microscopes to explain why this is the case.

4d1 mark

If the leaf sample used in Figure 1 were viewed under an electron microscope, ribosomes and cell membranes could be viewed clearly. Explain why.

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5a3 marks

A researcher wanted to examine specific cell organelles from animal cells, and decided to carry out cell fractionation to separate out the different cellular components. The first stage of cell fractionation is known as homogenisation and involves placing a tissue sample into a cold, isotonic buffer solution.

Explain why the sample needs to be placed in a cold, isotonic buffer solution. 

5b2 marks

After homogenisation, the researcher needed to prepare the sample for ultracentrifugation. Describe and explain how they would do this.

5c2 marks

Figure 1 shows the process of ultracentrifugation, and names some of the organelles isolated after each round in the centrifuge. 

Figure 1

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Identify the organelles isolated at the points marked X and Y in Figure 1

5d1 mark

Some nuclei isolated by the researcher can be seen in Figure 2. The nucleus diameter labelled A measures 6 μm.  

Figure 2

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Use the information provided in the question and in Figure 2 to calculate the magnification used by the researcher to view these nuclei. Give the magnification to the nearest whole number.

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1a4 marks

Biologists use two main types of microscope to examine cellular structure: optical microscopes and transmission electron microscopes (TEMs).  Give two advantages and two limitations of using a TEM to investigate cell structure.

1b2 marks

Figure 1 shows a transmission electron micrograph of part of an intestinal epithelial cell.

Figure 1

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Name the organelle labelled X and explain how these organelles facilitate the absorption of food molecules from the small intestine.

1c2 marks

The scale bar in Figure 1 represents a length of 0.2 μm.

Calculate the magnification of the drawing. Show your working.

1d2 marks

Explain why a transmission electron microscope gives a more detailed image of cell infrastructure than a light microscope.

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2a2 marks

Cholera bacteria can be viewed using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). Give one advantage of using a TEM and one advantage of using an SEM.

2b1 mark

An example of a unicellular eukaryotic organism, the amoeba, is shown in Figure 1.

Figure 1

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Name organelle A.

2c2 marks

Researchers wishing to study the structure of an amoeba should use a transmission electron microscope. Explain why.

2d4 marks

Name four structures in a eukaryotic cell that cannot be identified using an optical microscope.

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3a2 marks

Figure 1 shows an electron micrograph of a section through part of an alveolus from a lung and its adjacent tissue.

Figure 1

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The diameter of a human red blood cell is 7 µm. Calculate the magnification of Figure 1. Show your working.

3b2 marks

Explain what an artefact is in microscopy and why artefacts should be minimised.

3c4 marks

Cells X and Y are biconcave discs. Explain two advantages of a biconcave disc over a spherical cell of the same volume in transporting oxygen.

3d4 marks

Cell X is a eukaryotic cell. Give four features that may be found in a prokaryotic cell which are not found in cell X.

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4a4 marks

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope.

4b2 marks

Figure 1 below shows an image drawn from an electron micrograph of a plant cell.

Figure 1

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Give the name and function of the structures labelled W and Z.

4c2 marks

Researchers wishing to examine the detailed structure of the lower epidermis layer of a leaf have a variety of microscopy techniques available to them. Suggest the best technique that they should use to obtain detailed images of the leaf surface. Justify your answer.

4d2 marks

The theoretical resolving power of an electron microscope may often not be achieved in practice.  Explain why.  

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5a4 marks

Describe the steps required to calibrate the eyepiece graticule of an optical microscope.  

5b2 marks

Explain why the steps outlined in Question 5a) would need to be repeated when the observer changes to a more powerful objective lens. 

5c1 mark

Figure 1 shows the appearance of the scale of a stage micrometer. The length of the whole scale is 1.00 mm. Point A shows the point at which the edge of a human cheek cell appears in the microscope display. A typical cheek cell has diameter of approximately 50 μm.

Figure 1

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Indicate on Figure 1, with an arrow labelled B, the position of the opposite edge of the cheek cell. 

5d1 mark

Figure 2 shows an optical microscope’s field of view at a magnification of x200. 

The same stage micrometer is being used as in question 5 c). Calculate the distance represented by one subdivision of the eyepiece graticule scale at this magnification.

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1a2 marks

The 3D image below (Figure 1) shows a section through a plant tissue at a magnification of ×400. The distance between points C and D in the image is 20mm.

Figure 1

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Calculate the actual diameter (in µm) of the starch grain between points C and D.

1b2 marks

For the image shown in Figure 1:

i)
Name the type of microscope used to produce this image.

ii)
IndentGive one piece of evidence to support your answer to part i).
1c2 marks

Describe and explain two reasons why starch is a good storage carbohydrate for plant cells.

1d2 marks

State the test which would be used to show the presence of starch and the positive result of this test.

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2a2 marks

Scientists used a transmission electron microscope to study the structure of an unicellular, eukaryotic organism known as an amoeba.

Explain why.

2b3 marks

Name three structures in a eukaryotic cell that cannot be identified using an optical microscope.

2c1 mark

A transmission electron microscope (TEM) or a scanning electron microscope (SEM) can be used to observe prokaryotic cells.

Give one advantage of using a TEM, rather than an SEM.

2d2 marks

Give two general limitations of using a transmission electron microscope (TEM) to investigate cell structure.

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3a3 marks

Figure 1 shows part of a plant cell as seen with an electron microscope.

Figure 1

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Give three features shown in Figure 1 that show that this cell is eukaryotic.

3b2 marks

The scale bar in Figure 1 (measuring 45mm in length) on this drawing represents a length of 10μm.

Using these two values, calculate the magnification of the drawing. Show your working.

3c2 marks

Calculate the actual width of the cell in Figure 1 from A to B. Give your answer in micrometres (µm) and show your working.

3d2 marks

Give two ways in which a typical animal cell differs from the cell shown in Figure 1.

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4a1 mark

The diagram in Figure 1 shows a cholera bacterium. It has been magnified 40,000 times.

Figure 1

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Name structure E.

4b2 marks

A transmission electron microscope (TEM) or a scanning electron microscope (SEM) can be used by scientists to observe cholera bacteria.

Give two advantages of using an SEM rather than a TEM.

4c2 marks

Calculate the actual width of the cholera bacterium in Figure 1 between points G and F.

Give your answer in micrometres (µm) and show your working.

4d2 marks

Calculate the actual length of the flagellum of the cholera bacterium in Figure 1.

Give your answer in micrometres (µm) and show your working.

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5a2 marks

The diagram in Figure 1 is of a mitochondrion at a magnification of ×20,000. The distance between points A and B in the diagram is 6.4cm.

Figure 1

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Calculate the actual length of this mitochondrion in micrometres (µm). Show your working.

5b2 marks

The circumference of a mitochondrion (labelled C in Figure 1)  is 1.5µm. A student is making an accurate scale model of a mitochondrion for a school science project and wants to magnify a mitochondrion 50,000 times.

In centimetres (cm), what will be in the circumference of the student’s model?

5c2 marks

One scientific theory suggests that mitochondria are organelles that evolved from prokaryotic cells.

Give two pieces of evidence that support this theory.

5d2 marks

What advantage(s) do mitochondria provide to the cells that contain them?

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