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Cell Structure > Microscopes > Flashcards

Microscopes Flashcards

1
Q

Define the term ‘magnification’

A

The number of times larger an image appears, compared to the size of the original object

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2
Q

Define the term ‘organelles’

A

Small structures that are within cells - each of which has a specific function

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3
Q

Define the term ‘photomicrograph’

A

Photograph of an image seen using an optical microscope

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4
Q

Define the term ‘resolution’

A

The ability to be able to distinguish between two points clearly
The clarity of an image

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5
Q

Define the term ‘electron micrograph’

A

Photograph of an image seen using an electron microscope

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6
Q

What type of magnification do microscopes produce?

A

Linear magnification

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7
Q

List four reason as to why optical microscopes are still used in schools

A

cheap
easy to use
portable
used to study whole and living specimens

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8
Q

Explain simply how optical microscopes work

A

They relay on lenses to focus a beam of light

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9
Q

What is the maximum magnification of an optical microscope?

A

X1500

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10
Q

Explain why list microscopes can not magnify any higher than around X1500 effectively

A

As their resolution is limited - they cannot magnify any higher whilst also producing clear images

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11
Q

What is the maximum resolution of optical microscopes?

A

200 nm

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12
Q

What type of light does optical microscopes use?

A

Visible light

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13
Q

What are the four types of microscopes?

A

Optical
Laser Scanning
Scanning Electron
Transmission Electron

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14
Q

Explain why ribosomes cannot be seen using an optical microscope?

A

They are about 20nm diameter so are smaller than the resolution of the optical microscope (200nm)

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15
Q

Explain how to use light microscope

A

Place specimen onto the stage
Lens is placed over the specimen
Use the knob to focus the image while looking in the eyepiece
While viewing the image adjust the iris diaphragm for optimum light
Change the objectives X10 X40
Look at the specimen

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16
Q

What is the formula for calculating the total magnifying power of an optical microscope?

A

total magnification = objective lens magnifying power X magnifying power of the eyepiece lens

17
Q

How do modern digital microscopes display their image?

A

On a computer screen

18
Q

What is the alternative name for laser scanning microscope?

A

Confocal microscope

19
Q

Explain how laser scanning microscopes work

A

They use laser light to scan an object point by point and assemble the pixel information by computer, on a computer screen.

20
Q

The images produced by a laser scanning microscopes are high …. and show high…….

A

Resolution

Contrast

21
Q

Laser scanning microscopes have a special feature

what is it?

A

Depth selectivity

22
Q

Explain what depth selectivity is

A

It mean they can focus on structures at different depths within a specimen. It makes it useful to observe full and living specimens as well as cells

23
Q

What are the two main plans where laser scanning microscopes are used?

A

The medical profession and biological research

24
Q

Describe an example of how laser scanning microscopes are used in the medial profession

A

They’re used to observe fungal filaments in the cornea of the eye of a patient with a fungal corneal infection
This gives a swift diagnosis - therefore, giving a more effective treatment

25
Q

What are the two types of electron microscopes?

A

Transmission Electron

Scanning Electron

26
Q

What is the maximum resolution of a laser scanning microscope?

A

X2000

27
Q

Explain how an electron microscope works

A

They use a beam of fast travelling electrons that are fired from a cathode and focused by magnets

28
Q

Explain the types of images produced by electron microscopes?

A

They give clear and highly magnified images, especially compared to optical microscopes

29
Q

In preparation for use of a TEM microscope, explain what has to happen to the specimen in preparation

A

The specimen has to be chemically fixed by being dehydrated and stained

30
Q

Explain how transmission electron microscopes work

A

The beam of electrons shot by the cathode pass through the specimen and some of the electrons pass through and are focused onto the screen/photographic plate

31
Q

Explain the electron micrography that TEM’s produce

A

They form a 2D black and white images

32
Q

What is the maximum magnification formed by TEM’s?

A

X 2 million

33
Q

Explain how SEM microscopes work

A

The electron shot by the cathode don’t pass through the specimen as the electrons bounce off and are focused on screen

34
Q

Explain the image that SEMS give

A

The images that re produced re black and white and are 3D

Computer software programmes can also ass false colour

35
Q

List three disadvantages that are with both types of electron microscopes

A

Very expensive
Very large
Need training and skill to be able to use them

36
Q

Specimens used for electron microscopes have t be …. when used in the microscopes

A

Dead

37
Q

What are the effects the metallic salt stains used for staining can have on humans?

A

They can be potentially hazardous for humans

Cell Structure (3 decks)

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