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Bio A-level > Unit 2 Cells Microscopy > Flashcards

Unit 2 Cells Microscopy Flashcards

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Biology 101 flashcards
1
Q

How does the radiation travel in a Transmission Electron microscope?

A

The radiation pass throught the sample then into the objective lenses.

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2
Q

How does the radiation travel in a Scanning Electron microscope?

A

The radiation passes through the sample then into the objective lenses.

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3
Q

What is the radiation source in the electron microscope?

A

The radiation source is an electron beam.

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4
Q

What is the radiation source in the light microscope?

A

The radiation source is light

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5
Q

If there is higher resolution then what is the knock on effect?

A

Higher magnification

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6
Q

If there is higher magnification then what happens to the image?

A

The image appears to be larger

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7
Q

What instrument does the TEM use to detect the electrons?

A

Fluorescent screens

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8
Q

What instrument does the SEM use to detect the electrons?

A

Computer programme

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9
Q

What can help to focus the electron beam in a TEM?

A

Electromagnets

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10
Q

What can help to focus the electron beam in a light microscope?

A

Glass lenses

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11
Q

What is used to detect the light emitted by the light microscope?

A

The eyes

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12
Q

What is the definition of resolution?

A

Resolution is the smallest distance between two separate objects that can be distinguished

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13
Q

What is the difference in wavelengths between light and electrons?

A

Light has a larger wavelength whereas electrons have a smaller wavelength

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14
Q

How do the samples have to be when the light microscopes are used?

A

They can be either dead or alive

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15
Q

How do the samples have to be when the electron microscopes are used?

A

They have to be dead

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16
Q

What is the area around the sample must be within an electron microscope called?

A

The vacuum

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17
Q

If a sample within an electron microscope not surrounded by a vacuum what happens?

A

When the electron beam is fired from the electron gun it hits the air particles around which can ionise the particles so it produces random spurs of images.

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18
Q

What is the formula for magnification?

A

Magnification = Image size / Actual Size

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19
Q

How many mm in a cm?

A

10

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20
Q

How many mm in a metre?

A

1000

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21
Q

How many micrometres in a mm?

A

1000

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22
Q

How many nanometres in a micrometre?

A

1000

23
Q

What is the standard form formula for 1 nm?

A

1 x 10^-9

24
Q

What is the standard form formula for 1 micrometre?

A

1 x 10^-6

25
Q

What is the maximum resolution for a light microscope?

A

0.2 micrometres apart

26
Q

What is the maximum resolution of electron microscopes?

A

0.1 nanometres apart

27
Q

What is the maximum magnification for light microscopes?

A

2000x

28
Q

What is the maximum magnification for electron microscopes?

A

Over 500,000x

29
Q

What are the limitations for electron microscopes?

A

Expensive, stored at specific temp and difficult to use

30
Q

What are the pros of electron microscopes?

A

Have high magnifications and higher resolutions so give more detail

31
Q

What are the limitations of light microscopes?

A

Have low resolution and low magnification so less detail than the electron microscopes

32
Q

What are the pros of light microscopes?

A

Easy to use, cheap and don’t require a specific temp to be stored in

33
Q

What is the formula for calculating the magnification of an object?

A

Magnification = image size / actual size

34
Q

What is cell fractionation?

A

Cells are broken up and different organelles within the cell are separated out

35
Q

What are 3 things that a solution must be like in order to undergo cell fractionation?

A

Cold isotonic and be a buffered solution

36
Q

Why is a cell put in a cold area?

A

To reduce enyme activity that might break down organelles.

37
Q

Why is a cell put in an isotonic surrounding?

A

To prevent the organelles from shrinking or becoming swollen as a result of osmotic gain or loss

38
Q

Why is a cell placed in a buffered solution?

A

So that the pH doesn’t fluctuate this could lead to enzyme activity being decreased due to denaturation

39
Q

What are the 2 stages of cell fractionation?

A

Homogenation and ultracentrifugation

40
Q

How does homogentaion work?

A

Homogentaion is when the cells are broken by a homogeniser releasing the organelles.

41
Q

What are the products of homogenation?

A

The homogenate - resultant fluid
The pallet - large pieces of debris and cell

42
Q

What happens to the homogenate after homogenation?

A

The homogenate is filtered so that it removes any large pieces of debris or any unbroken cells

43
Q

What is the process of Ultracentrifugation?

A

Fragments in the filtered homogenate are separated in a machine called the centrifuge

44
Q

What does the centrifuge do?

A

The centrifuge spins tubes of the homogenate at very high speeds in order to create a centripetal force.

45
Q

What happens to the components of the cells within the homogenate after ultracentrifugation?

A

The heaviest organelles such as the nuclei are the densest and so lay at the bottom of the tube forming a pellet.
The rest of the organelles are less dense and so they form the fluid called the supernatant

46
Q

What happens to the supernatant after ultracentrifugation?

A

It is filtered and then put into another tube and spun at even faster speeds than before

47
Q

What are the top 3 heaviest organelles within the human cell?

A

Nucleus then mitochindria then lysosymes

48
Q

What is the heaviest organelle after the nucleus in the plant cell?

A

Chloroplast

49
Q

What is a photomicrograph?

A

An image produced on the screen and then photographed

50
Q

Using a light microscope how is the size of the objects measured?

A

Using a eyepiece granule

51
Q

How is the eyepiece graticule calibrated? Using what instrument?

A

Using a stage micrometer

52
Q

What is the lowest magnification on light microscope?

A

x4

53
Q

What is the total magnification ?

A

eyepiece lens x objective lens

54
Q

How is the eyepiece graticule calibrated?

A

The EPG and the stage micrometer scale are aligned

Bio A-level (16 decks)

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