The Microscope in Cell Studies (CIE A Level Biology)

Which of the following is not a correct description of a light microscope or an electron microscope?

A prokaryotic cell is magnified 50 000 times by an electron microscope, it has a diameter of 1 µm.

What is the diameter of the cell in an electron micrograph?

The electron micrograph below shows the organelles in a leaf cell.

A ruler has been added to show the size of the image alongside the scale bar which shows the distance that represents 5 µm.

What is the magnification of this image?

The electron micrograph below shows a root vascular system.

The magnification of the image is x200 and Y has a diameter of 1 cm when measured using a ruler.

What is the diameter of the cell labelled Y?

To view the actual width of a transverse section of a xylem vessel with a x40 lens, which steps are needed?

1	Measure the width of the xylem vessel using an eyepiece graticule.
2	Calibrate the eyepiece graticule using a stage micrometer on x10 objective lens.
3	Convert from mm to µm by multiplying by 10-3
4	Multiply the number of eyepiece graticule units by the calibration of the eyepiece graticule.

The electron micrograph of the plant cell has a 2 cm scale line labelled 5 µm.

What is the magnification?

Erythrocytes (red blood cells) have a diameter of 7000 nm. Pancreatic cells have a diameter of 35 µm.

Which of these statements is correct about the relative sizes of these cells?

The table shows some approximate units for measuring the diameters of alveoli, white blood cells and the width of plant cell walls.

Which of the rows show the best units for measuring these structures?

	Diameters of alveoli	Diameters of white blood cells	Width of plant cell walls
A	mm	nm	µm
B	cm	µm	nm
C	µm	nm	µm
D	µm	µm	nm

The following statements describe slide preparation. 

Which one would refer to a wet mount preparation of a slide for observation with a light microscope? 

The following statements describe drawing a scientific drawing.

Which is not a correct statement about drawing scientifically?

The actual length of a cell structure is 6 µm.

A student was asked to write an equation that could be used to calculate the magnification of an electron micrograph of this cell structure. The student used the letters q to u in their equation.

q = The length of the cell structure in the image in cm

r = The length of the cell structure in the image in mm

s = 1000

t = 

u = 6

Which of the following would be the correct equation to calculate the magnification?

A stage micrometer with small divisions of 0.1 mm was used to calibrate a graticule. This is shown in the diagram below.

A slide of a plant cell was placed on the stage in place of the stage micrometer. 

 What is the width of the chloroplast below?

Cells can vary considerably in their diameter.

Typical diameters of cells are:

• Eukaryotic cells, such as a white blood cell          1.5 x 10¹ µm
• Prokaryotic cells, such as Streptococcus              7.5 x 10² nm

Use these measurements to find the maximum number of each cell that could fit along a 1 cm line.

	Number of white blood cells	Number of Streptococcus cells
A	6.7 x 100	1.3  x 102
B	6.7 x 101	1.3  x 103
C	6.7 x 102	1.3  x 104
D	6.7 x 103	1.3  x 105

A light microscope with an eyepiece lens of x5 and an objective lens of x8 was used to draw the diagram of a transverse section through a leaf, as shown below.

The actual length of the leaf is 7.5 mm. What is the magnification of the diagram?

The diagram below is viewed through an eyepiece with a graticule showing the stage micrometer below. The stage micrometer has divisions 0.1 mm apart.

The eyepiece is then used to examine a blood smear.

How many of the graticule divisions will cover the diameter of a white cell of 12.5 µm?

A light microscope is used to observe a specimen under green light with a wavelength of 510 nm.

If the same specimen, with all other conditions kept constant, is viewed under red light with a wavelength of 650 nm, what effect would this have on the magnification and resolution of the microscope?

	magnification	resolution
A	stays the same	increased
B	stays the same	decreased
C	increased	decreased
D	decreased	increased

The diagram below shows a view through a microscope eyepiece with a graticule scale and a stage micrometer using a magnification of x400.

Using the magnification of x400, a chloroplast was measured to be 4 eyepiece graticule divisions in length.

How long is the chloroplast?

The diagram below shows a view through a microscope eyepiece with a graticule scale and a stage micrometer, with divisions 0.1 mm apart.

What is the area of the field of view at this magnification? ( = 3.14)

A student was using an eyepiece graticule with 100 small divisions. The stage micrometer they were using had a scale with 50 divisions, each of them 0.04 mm apart.

Using a x40 objective lens, the whole length of the stage micrometer lined up with 15 divisions of the eyepiece graticule.

What is the length of the 100 division scale of the eyepiece graticule at this magnification?