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stuff ni jas > centrifugation > Flashcards

centrifugation Flashcards

1
Q

what is a centrifuge used for?

A

separation of particles or microorganisms from the suspended fluid using centrifugal force

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2
Q

what is another name for centrifugal force?

A

g-force

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3
Q

particles separate according to what?

A

size
shape
viscosity of medium
rotor speed
density

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4
Q

when can centrifugation only be used?

A

only when the dispersed material is denser than the medium

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5
Q

true or false: higher density particles sediment in influence of gravitational field

A

true

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6
Q

what is the movement under gravitational force called?

A

sedimentation

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7
Q

true or false: when the centrifugal force is applied by the centrifuge, the particles move slower

A

false, they move faster

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8
Q

relative centrifugal force is expressed as?

A

a multiple of the acceleration (G) due to gravity (g)

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9
Q

what kind of force does a sample experience in a centrifuge?

A

centrifugal force

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10
Q

what is the rate of sedimentation dependent on?

A

the centrifugal field

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11
Q

what is the applied centrifugal force determined by?

A

the radial distance of the particle from the axis of rotation

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12
Q

how is centrifugal field generally expressed?

A

in multiples of gravitational speed (9.8m/s^2)

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13
Q

RCF is the ratio of what?

A

ratio of centrifugal acceleration (G) and gravitational acceleration (g)

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14
Q

what is the formula for RCF?

A

RCF = 1.12 x 10^-5 (RPM)^2 (r)

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15
Q

what are the 2 types of centrifuge rotors?

A

fixed angle and swinging bucket

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16
Q

what is a fixed angle rotor?

A

particles only have a short distance to travel before pelleting
shorter run time
widely used

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17
Q

what is a swinging bucket rotor?

A

longer distance of travel for better separation such as in density gradient centrifugation
easier to withdraw supernatant without disturbing the pellets

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18
Q

high speed centrifuges can handle what kind of samples?

A

larger sample volumes

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19
Q

how much rpm can larger centrifuges reach?

A

high rpm, 30000rpm or 15,000-20,000rpm

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20
Q

what kind of sample containers can large high speed centrifuges hold?

A

various test tubes
bottles
microliter plates

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21
Q

where are ultracentrifuges used?

A

studies of membrane fractionation

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22
Q

how much rpm can ultracentrifuges reach?

A

70,000rpm or 65,000rpm

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23
Q

how does an ultracentrifuge work?

A

it can separate molecules in batch or continuous flow systems
during the run, particles will migrate through the test tube at different speed depending on their physical properties and properties of the solution

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24
Q

high speed or ultracentrifuge: large sample capacity

A

high speed

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25
Q

high speed or ultracentrifuge: normally refrigerated

A

high speed

26
Q

high speed or ultracentrifuge: expensive

A

ultra

27
Q

high speed or ultracentrifuge: research applications

A

both

28
Q

high speed or ultracentrifuge: limited lifetime

A

ultra

29
Q

high speed or ultracentrifuge: 15,000-20,000rpm

A

high speed

30
Q

high speed or ultracentrifuge: need special rotors

A

ultra

31
Q

high speed or ultracentrifuge: care in use, balance is critical

A

ultra

32
Q

high speed or ultracentrifuge: 65,000rpm (100,000’s x g)

A

ultra

33
Q

where are microcentrifuges used?

A

process small volumes of biological molecules, cells, or nuclei

34
Q

how much liquid does a microcentrifuge hold?

A

0.5-2mL

35
Q

what is the angular speed of a microcentrifuge?

A

12,000-13,000rpm

36
Q

true or false: microcentrifuges can fit on a table top and have rotors that can change speed quickly

A

true

37
Q

true or false: microcentrifuges should always be refrigerated

A

false, they can or cannot be

38
Q

what type of centrifuge is used to separate erythrocytes, blood samples, coarse precipitates, and cells

A

small bench centrifuge

39
Q

what is the speed and RCF of a small bench centri?

A

speed 4,000-6,000 rpm
RCF 3,000-7,000g

40
Q

at what speed and RCF are small samples sedimented?

A

speed 8,000-13,000rpm
RCF 10,000g

41
Q

how long does a small bench centri sediment a small volume

A

1-2mins

42
Q

small bench top or microcentrifuge: common in biochem/molbio/bio labs

A

micro

43
Q

small bench top or microcentrifuge: can take up to 100 test tubes depending on diameter

A

small bench

44
Q

small bench top or microcentrifuge: can take force up to 15,000g

A

micro

45
Q

small bench top or microcentrifuge: with or without refrigeration

A

both

46
Q

small bench top or microcentrifuge: common in clinical labs (blood/plasma/serum separation)

A

small bench

47
Q

ssmall bench top or microcentrifuge: slow speed

A

small bench

48
Q

small bench top or microcentrifuge: can take small volumes up to 2mL

A

micro

49
Q

kind of gradient media: preserves morphology and activity of subcellular fractions

A

sucrose and ficoll

50
Q

kind of gradient media: isopycnic density gradient technique

A

cesium chloride
potassium bromide

51
Q

kind of gradient media: bec of low osmolarity, low viscosity and large particle size, it is suitable for cell separation, bacteria viruses, and subcellular organelles

A

percoll

52
Q

kind of gradient media: isolation of membrane fractions via floatation

A

metrizamide
nycodenz

53
Q

kind of gradient media: cell fractionation

A

renografin

54
Q

required centrifugal force of nuclei

A

800-1,000g

55
Q

required centrifugal force of mitochondria, chloroplasts, microbodies

A

20,000-30,000g

56
Q

required centrifugal force of RER membranes

A

50,000-80,000g

57
Q

required centrifugal force of plasma membranes, SER

A

80,000-100,000g

58
Q

required centrifugal force of free ribosome particles

A

150,000-300,000g

59
Q

what is the material of most rotors?

A

aluminum or titanium

60
Q

true or false: aluminum rotors are corrosion resistant, while titanium is not

A

false, titanium is corrosion resistant and aluminum is not

61
Q

what are the applications of centri in biological sciences?

A

separate cellular and subcellular components
separate one cell form another
removing cells from suspended liquid
isolating viruses and macromolecules
study effects of centri force on cells, embryos, protozoa
determine certain properties abt cells

stuff ni jas (20 decks)

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