1.1.1 - Cell Structure (Microscopy) Part 1 & 3

Question 1

State the resolution and magnification that can be achieved by a light microscope.

Answer 1

Resolution - 200nm

Magnification - x1,500

Question 2

State the resolution and magnification that can be achieved by a transmission electron microscope.

Answer 2

Resolution - 0.2nm

Magnification - x500,000

Question 3

State the resolution and magnification that can be achieved by a scanning electron microscope.

Answer 3

Resolution - 0.2nm

Magnification - x100,000

Question 4

Explain the difference between magnification and resolution.

Answer 4

Magnification - The number of times larger an image is

Resolution - The ability to distinguish between two separate points

Question 5

Explain what staining (in microscopy) is.

Answer 5

Staining refers to any process that helps to reveal or distinguish different features in a sample.

Question 6

Explain the need for staining samples when using a light microscope.

Answer 6

Many biological materials are not coloured, so you cannot see any details. Material may also become distorted when being cut into sections. Coloured stains are chemicals that bind to other chemicals on or in the specimen, allowing for the specimen to be seen.

Question 7

Explain the need for staining samples when using a transmission electron microscope.

Answer 7

The final image produced from an electron microscope is always in black, white and grey. Colours are added using a specialised computer software to reveal any features in the sample that may not be as visible as a greyscale image.

Question 8

What is the difference between a TEM and an SEM? List 3 differences.

Answer 8

TEM:
- Electron beam passes through the thin sample
- Final image is 2D
- Magnification = x500,000
SEM:
- Electron beam bounces off the sample
- 3D image of the surface is produced
- Magnification = x100,000

Question 9

List some advantages of an electron microscope.

Answer 9

• The resolution is 1000x more than light microscope.
• They can produce detailed images of cell organelles.
• SEM produces 3D images which can reveal cellular or tissue arrangements.

Question 10

List some limitations of an electron microscope.

Answer 10

• Samples must be placed in vacuum as electron beams deflect off air particles.
• They are expensive.
• The preparing of samples and use of an electron microscope require a high level of skill.