2.1 Microscopy

Question 1

How many lenses does a light microscope have, name them? (2 marks)

Answer 1

2- eyepiece lens, objective lens

Question 2

How is resolution adjusted using a light microscope? (2 marks)

Answer 2

Fine focusing knob
Coarse focusing knob

Question 3

Name 4 ways to prepare a sample to view under a microscope. (4 marks)

Answer 3

Dry mount
Wet mount
Squash slices
Smear slides

Question 4

Describe a dry mount. (2 marks)

Answer 4

Solid specimens cut into very thin slices.
Placed on slide and a cover slip is placed over the sample.

Question 5

Describe a wet mount. (2 marks)

Answer 5

Specimens are suspended in liquid.
A cover slip is placed on from an angle.

Question 6

Describe a squash slide. (2 marks)

Answer 6

Wet mount prepared first.
Then lens tissue is used to press down on the cover slip.

Question 7

Describe a smear slide. (2 marks)

Answer 7

Edge of a slide is used to smear the sample.
A cover slip is placed over the sample.

Question 8

Why are stains sometimes used when viewing samples? (2 marks)

Answer 8

Increase contrast of components.
Allows components to become visible so they can be identified.

Question 9

How does gran staining work? (2 marks)

Answer 9

Gram positive bacteria retain the stain.
Gram negative bacteria have thinner cell walls so they lose the stain.

Question 10

Why is acid-fast staining used? (1 mark)

Answer 10

Used to differentiate between sources of Mycobacterium.

Question 11

Explain how a student can add a stain to a wet mount slide. (2 marks)

Answer 11

Put a drop of stain next to one edge of the cover slip and a piece of paper towel next to opposite edge.
The paper towel will draw the stain under the slip.

Question 12

What two stages are needed to prepare a large tissue specimen for light microscopy? (2 marks)

Answer 12

Sectioning
Staining

Question 13

Why do most specimens need to be stained? (1 mark)

Answer 13

Many cells are colourless, so detail cannot be seen unless stained.