The Microscope in Cell Studies (CIE A Level Biology)

Fig. 1 is a drawing of part of a plant cell as seen with an electron microscope. The scale bar (measuring 45 mm in length) on this drawing represents a length of 10 μm.

Fig. 1

Calculate the magnification of the drawing in Fig. 1

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

Fig. 2 is a drawing of a mitochondrion at a magnification of ×20 000. The distance between points A and B in the diagram is 6.4 cm.

Fig. 2

Calculate the actual length of the mitochondrion in Fig. 2 in micrometres (µm).

The circumference of a mitochondrion, labelled C in Fig. 2, is 1.5 µm. 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.

Calculate (in cm) what the circumference of the student’s model will be.

A student is given a sample of plant tissue.

Describe how the student would prepare a sample of cells from this tissue to be viewed using a light microscope.

Describe how the student in part (a) would then view their sample of cells using a light microscope.

Identify two structures in a eukaryotic cell that cannot be identified using a light microscope.

Fig. 1 below shows a cross-section of a leaf taken using a light microscope with a magnification of x250.

Fig. 1

Fig. 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.

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

Explain why.

Outline the general advantages and disadvantages of using an electron microscope.

Fig. 2 below shows an image of algae taken using an electron microscope.

SecretDisc, CC BY-SA 3.0, via Wikimedia Commons

Fig. 2

For the image shown in Fig. 2

[1]

A student decided to produce a biological drawing of a plant cell they were viewed using a light microscope.

Give four conventions that the student must be sure to follow for their diagram to be classed as a biological drawing.

In order to produce a scale line for their biological drawing in part a), the student needs to calculate the size of each eyepiece graticule subdivision. Fig. 1 shows the field of view of the light microscope used by the student at a magnification of x200. The student is told that each subdivision on the stage micrometer represents 10 µm.

Fig. 1

Calculate the distance represented by one subdivision of the eyepiece graticule scale at this magnification.

The student in parts a) and b) wants to be able to draw more detail of the plant cell infrastructure.

Explain why an electron microscope would give a more detailed image of the plant cell infrastructure than a light microscope.

With reference to resolution, explain the limitations of using a light microscope.

Fig. 1 shows a photomicrograph of onion epidermal cells at a magnification of x250.

Fig. 1

Draw a biological drawing of the cells in Fig. 1.

[5]

Name three organelles that are not visible in Fig. 1.

[3]

One of the cells of the image in Fig. 1 was measured to be 24 mm.

Calculate the actual width of one of the cells in Fig. 1. Give your answer in micrometres (µm).

Describe how a student would make a temporary mount of some onion epidermal tissue.

A student used a light 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).

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

Describe the steps required to calibrate the eyepiece graticule of a light microscope using a stage micrometer.

Explain why the steps outlined in part (b) would need to be repeated when the student changes to a more powerful objective lens.

Fig. 1 shows the appearance of the scale of a stage micrometer. The length of the whole scale is 1 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.

Fig. 1

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

Give two advantages and two limitations of using electron microscopes to investigate cell structure.

Fig. 1 shows an electron micrograph of part of an intestinal epithelial cell.

Fig. 1

Name the structures labelled X.

Use the scale bar to calculate the magnification of the drawing in Fig. 1.Show your working.

The two mitochondria identified in Fig. 1 appear to be different in shape.

Suggest two reasons for this difference.

Describe the process of making a temporary mount of a piece of plant tissue that would allow observation of starch grains within a cell with a light microscope.

Fig. 1 shows two micrographs.

Fig. 1

Compare the images shown by the two micrographs.

State the role of the cell type visible in Fig. 1.

[1]

Explain the adaptations of these cells.

[3]

A student doctor wanted to take a number of different measurements from a sample of blood cells in a blood smear. 

They used a light microscope with an eyepiece graticule as part of their method, but they did not use a stage micrometer.

Identify the type of error this would lead to and explain the effect on their data. 

Fig. 2 below shows a stage micrometer scale and an eyepiece graticule in a light microscope. The upper scale is the micrometer while the lower scale is the eyepiece graticule.

The length of one division on this stage micrometer is 0.1 mm.

Fig. 2

Calculate the actual length of one eyepiece graticule division using this stage micrometre. Give your answer in µm and show your working.

The photomicrograph in Fig. 3 was taken using the same microscope and the same lenses as part (b).

The same eyepiece graticule was also used and is shown in Fig. 3.

Use the calibration of the eyepiece graticule unit from part (a) and the information in the photomicrograph to estimate the actual length in μm of the region of plant tissue shown between C and D. 

Draw a biological drawing of at least four cells from Fig. 3, including the cell labelled C-D. Your drawing should be drawn to scale at x1000 magnification.

A typical animal cell is surrounded by a cell membrane with a mean thickness of 8 nm, measured using electron microscopy.

A light microscope-generated image of the whole cell itself measures 5 cm across at a magnification of x1250.

Calculate the number of times wider the whole cell is than the thickness of its membrane. 

A light microscope and an electron microscope were used to examine the contents of a plant cell.

The light microscope was used at two different magnification settings to produce the images shown in Fig .1. The electron microscope image is also shown in Fig.1 

In all three images the field of view contained the same piece of biological material. 

Fig.1 

Suggest reasons for the differences in the appearance of the three images in Fig. 1.

Give two possible names of cell components that could be shown in Fig. 1.

Assume that the setup of the microscopes and sample preparation has been carried out to give the best possible view of the specimens under observation in each case.