Chapter 2: 2.1

Question 1

Why are microscopes important?

Answer 1

• Allow us to understand diseases
• Help us see how new life is formed
• Allow us to manipulate processes in life

Question 2

What is the function of a microscope?

Answer 2

It enables us to magnify an object hundreds, thousands and hundreds of thousand of times

Question 3

What does the cell theory state?

Answer 3

• Both plant and animal tissues is composed of cell
• Cells are the basic units
• Cells only develop from cells

Question 4

When was the first light microscopes developed?

Answer 4

In the 16th and 17th century

Question 5

Why are light microscopes commonly used in biology?

Answer 5

• Easily available
• Cheap
• Can be used outside in the field
• Can be used to observe living organisms and
  prepared specimens

Question 6

Why has the cell theory developed over time?

Answer 6

This is because more microscopes with higher magnification and resolution has been developed

Question 7

How does compound light microscope work?

Answer 7

• The objective lens produces a magnified image which is magnified again by the eyepiece lens
• This combination produces images at high magnification and reduces chromatic aberration more than a simple light microscope

Question 8

What are the different ways of preparing a (or types of) slide?

Answer 8

• Dry Mount
• Wet Mount
• Squash Slides
• Smear Slides

Question 9

How do you prepare a dry mount slide?

Answer 9

1. The solid specimen is viewed whole or cut into very thin slices with a sharp blade (know as sectioning)
2. The specimen is placed at the middle of the slide

Example - can be used for viewing hair or pollen whole

Question 10

How do you prepare a wet mount slides?

Answer 10

1. Specimens are suspended in liquid
2. A cover slip is placed on from an angle, like so:
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Question 11

How do you prepare squash slides?

Answer 11

A lens tissue is used to gently press down the cover slip

N.B. Care must be taken that the cover slip is not broken when being pressed

Question 12

How do you prepare a smear slide?

Answer 12

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

Example: A sample of blood is a smear slide

Question 13

Why are images at low contrast with a basic light microscope?

Answer 13

Most cells don’t absorb a lot of light

Question 14

What is diffraction?

Answer 14

Bending of light as it passes close to the edge of an object

Question 15

How do you prepare a sample for staining?

Answer 15

1. Sample is placed on a slide and allowed to air dry
2. This is then heat fixed by passing through the flame
3. The specimen will adhere to the slide and absorb the stains

Question 16

What is gram stain technique used for?

Answer 16

To separate bacteria into two groups

Gram-positive bacteria and Gram-negative bacteria

Question 17

How do you carry out gram stain technique?

Answer 17

1. Crystal violet is first applied to bacterium slide then iodine which fixes dye
2. The slide is the washed with alcohol
   - if it is gram positive bacteria it retains the crystol violet stain and will appear blue/purple under microscope
   - if gram negative bacteria it will lose its’ stain and are then stained with a counter stain (i.e. safrnin dye). makin them appear red

Question 18

Why are gram-negative bacteria not suspectable to penicillin?

Answer 18

Because they have thin cell walls and penicillin inhibits formation of cell walls

Question 19

*What is the acid-fast technique used for?

Answer 19

*To differentiate species of mycobacterium from other bacteria

Question 20

How do you carry out acid-fast technique?

Answer 20

1. Lipid solvent is used to carry out carbolfuchsin dye into the cell being studied
2. The cells are then washed with a dilute acid alcohol solution {Mycrobacterium is not affected by acid-alcohol and retain carbolfuchsin stain, which is bright red}
3. Other bacteria lose the stain and get exposed to methylene blue stain

Question 21

What stages are involved in preparation of slides?

Answer 21

1. Fixing
   - Chemicals are used to preserve specimens in as natural a state as possible
2. Sectioning
   - Specimens are dehydrated w/ alchols
   - They’re then placed in a mould w/ wax or resin to form a hard block
   - These can be sliced with a knife called a microtome
3. Staining
   - Specimens are treated with multiple stains to show different structures
4. Mounting
   - Specimens are secured to a microscope slide and a cover slip is placed on top