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Biology > Microscopes > Flashcards

Microscopes Flashcards

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1
Q

Why do light microscopes have a poor resolution?

A

Poor resolution due to the long wavelength of light

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2
Q

Which microscopes can be used on living samples and a color image is obtained

A

Light micrscopes

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3
Q

What does resolution mean

A

resolution is the ability of a microscope to distinguish between two different points of a specimen

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4
Q

How is resolution determined in
1. Optical microscopes
2. Electron microscopes

A
  1. Determined by the wavelength of light
  2. Determined by the wavelength of the beam of electrons
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5
Q

What is magnification

A

Magnification refers to how many times larger the image is compared to the object size

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6
Q

What is a dry mount sample preparation

A

This is when thin dry slices or whole dry specimens are viewed with just the coverslip placed on top e.g hair or plant tissue

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7
Q
  1. What is a wet mount sample preparation
  2. What specific type of animal can be viewed this way
A
  1. This is when water or a stain is added to the specimen before lowering the coverslip with a needle to prevent air bubbles
  2. Aqauatic amimals
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8
Q

What’s a squashed slide

A

squash slides are wet mounts which have had the coverslip squasheed down on it to ensure the sample is thin enough for light to pass through

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9
Q

What are smear slides used for

A

There are used when examining blood cells in a blood sample

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10
Q

What is differential staining

A

differential staining is a technique which involves many chemical stains being used to stain different parts of a cell in different colors

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11
Q
  1. Which 2 stains are positively charged
  2. What do they do
A
  1. Crystal violet’and methylene blue
  2. These are attracted to and stain negatively charged material
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12
Q
  1. Which two stains are negatively charged
  2. What do they do
A
  1. Nigrosin and Congo red
  2. These cannot enter the cells as cytosine repels them therefore they create a stained background and the unstained cells then stand out
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13
Q

What are the four types of cell preparation

A
  1. Dry mount
  2. Wet mount
  3. Smear slide
  4. Squash slide
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14
Q

What’s a slide

A

Thin flat piece of glass used to hold objects for examination under a microscope (75 by 26mm)

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15
Q

What’s a stain

A

Colored chemicals that bind to molecules on or in a specimen

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16
Q

Gram stainingis a type of differential stain where you use two different stains
1. to identify what
2. What are the two stains

A
  1. To identify what type of bacteria is present
  2. Crystal violet and safranin
17
Q

What is the process of adding crystal violet to the stains

A
  1. Add crystal violet
  2. Add iodine to fix the stain
  3. Alcohol added to wash any unbound stain to avoid it all looking dark
18
Q
  1. What color do gram positive bacteria appear
  2. Why
A
  1. Blue/purple
  2. The stain is retained due to the thicker peptidoglycan cell wall absorbing the dye
19
Q
  1. Why can’t gram negative bacteria absorb crystal violet
  2. What is added instead
  3. What color does this turn the bacteria
A
  1. Peptidoglycan cell wall is thin so they don’t retain the stain due to the thinner wall
  2. Safranin is used as a countertstain
  3. Red
20
Q

1.Why must electron microscope be used in a vacuum/only dead specimen

A
  1. Electrons are absorbed by air therefore only non living specimen can be examined
21
Q

Why do electron microscopes have a high wavelength

A

A beam of electrons have a very short wavelength therefore a high resolution

22
Q

What color is the imagine produced in an em microscope and why

A

Black and white as the sample must be stained

23
Q

How is the image created by an em microscope

A

Image created using an electromagnet to focus the beam of the negative electrons

24
Q

What are the two types of em microscopes

A
  1. Transmission electron microscope
  2. Scanning electron microscopes
25
Q

Which type of electron microscope needs thin specimen and why

A

Transmission electron microscopes need an extremely thin specimen as the electron gun passes a beam of electrons through the specimen whereas in scanning electron microscopes the electrons are beamed onto the surface and scattered in different ways depending on the contours

26
Q

1.why do some parts of the specimen in TEM appear darker
2. What type of image is produced

A
  1. They absorbed the electron
  2. Image is produced in 2D
27
Q
  1. What type of image is produced in SEM
  2. Are TEM specimen stained
A
  1. 3D
  2. Yes
28
Q
  1. What type of microscope is the laser scanning microscope
A
  1. Fluorescent microscope
29
Q

1.what type of image do laser scanning microscopes produce
2.Is the image high or low resolution

A

1.3D and 2D
2.high resolution

30
Q
A

Biology (3 decks)

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