Microscopes Flashcards

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1
Q

What is the equation that links image size, magnification and real size?

A

Magnification= image size/ real size

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2
Q

Define magnification

A

how many times bigger the image is when compared to the object

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3
Q

Define resolution

A

minimum distance apart 2 objects can be to appear as separate items

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4
Q

What is the link between light and resolution

A

Longer wavelength than electrons so limited resolution

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5
Q

What is the limit of a light and electron microscope?

A

light= 0.2 micrometres

electron=0.1 nanomentres

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6
Q

What is the equation of the mitotic index?

A

number of dividing cells in field of view/ number of cells in total

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7
Q

Define cell fractionation

A

process where cells are broken up and the different organelles they contain are separated out

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8
Q

Describe homogenation

A

homogeniser breaks up cells to release the organelles
resultant fluid= homogenate
filter to remove debris and large cell chunks

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9
Q

Define ultracentrifugation

A

process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge.

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10
Q
What speed are \_\_\_\_\_\_ spun at?
Nuclei 
Lysosomes
Chloroplast
Mitochondria
Ribosomes
A

nuclei= 1000
mitochondria= 3500
lysosomes= 16500
ribosomes=100,000

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11
Q

Name the two types of electron microscopes

A

Transmission electron microscope

Scanning electron microscope

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12
Q

What is the resolving power of the TEM and why is this not often achieved in practise?

A

0.1 nm
higher electron beam required which can destroy the specimen
difficulty in preparing the specimen

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13
Q

What are the main limitations of the TEM

A

specimen must be extremely thin
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts

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14
Q

What are the main limitations of the TEM

A

specimen must be extremely thin
Image is 2D ( can build 3D via many images which is slow and complicated)
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts

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15
Q

What are the limitations of the SEM?

A

whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts

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16
Q

Name the resolution power of the SEM

A

20nm

17
Q

Compare the optical and TEM microscope

A
  1. TEM use electrons and optical use light;
  2. TEM allows a greater resolution;
  3. (So with TEM) smaller organelles/named cell
    structure can be observed
    OR
    greater detail in organelles/named cell structure
    can be observed;
  4. TEM view only dead/dehydrated specimens and
    optical (can) view live specimens;
  5. TEM does not show colour and optical (can);
  6. TEM requires thinner specimens;
  7. TEM requires a more complex/time consuming
    preparation;
  8. TEM focuses using magnets and optical uses
    (glass) lenses;