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centrifugation Flashcards

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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
high speed or ultracentrifuge: normally refrigerated
high speed
26
high speed or ultracentrifuge: expensive
ultra
27
high speed or ultracentrifuge: research applications
both
28
high speed or ultracentrifuge: limited lifetime
ultra
29
high speed or ultracentrifuge: 15,000-20,000rpm
high speed
30
high speed or ultracentrifuge: need special rotors
ultra
31
high speed or ultracentrifuge: care in use, balance is critical
ultra
32
high speed or ultracentrifuge: 65,000rpm (100,000's x g)
ultra
33
where are microcentrifuges used?
process small volumes of biological molecules, cells, or nuclei
34
how much liquid does a microcentrifuge hold?
0.5-2mL
35
what is the angular speed of a microcentrifuge?
12,000-13,000rpm
36
true or false: microcentrifuges can fit on a table top and have rotors that can change speed quickly
true
37
true or false: microcentrifuges should always be refrigerated
false, they can or cannot be
38
what type of centrifuge is used to separate erythrocytes, blood samples, coarse precipitates, and cells
small bench centrifuge
39
what is the speed and RCF of a small bench centri?
speed 4,000-6,000 rpm RCF 3,000-7,000g
40
at what speed and RCF are small samples sedimented?
speed 8,000-13,000rpm RCF 10,000g
41
how long does a small bench centri sediment a small volume
1-2mins
42
small bench top or microcentrifuge: common in biochem/molbio/bio labs
micro
43
small bench top or microcentrifuge: can take up to 100 test tubes depending on diameter
small bench
44
small bench top or microcentrifuge: can take force up to 15,000g
micro
45
small bench top or microcentrifuge: with or without refrigeration
both
46
small bench top or microcentrifuge: common in clinical labs (blood/plasma/serum separation)
small bench
47
ssmall bench top or microcentrifuge: slow speed
small bench
48
small bench top or microcentrifuge: can take small volumes up to 2mL
micro
49
kind of gradient media: preserves morphology and activity of subcellular fractions
sucrose and ficoll
50
kind of gradient media: isopycnic density gradient technique
cesium chloride potassium bromide
51
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
percoll
52
kind of gradient media: isolation of membrane fractions via floatation
metrizamide nycodenz
53
kind of gradient media: cell fractionation
renografin
54
required centrifugal force of nuclei
800-1,000g
55
required centrifugal force of mitochondria, chloroplasts, microbodies
20,000-30,000g
56
required centrifugal force of RER membranes
50,000-80,000g
57
required centrifugal force of plasma membranes, SER
80,000-100,000g
58
required centrifugal force of free ribosome particles
150,000-300,000g
59
what is the material of most rotors?
aluminum or titanium
60
true or false: aluminum rotors are corrosion resistant, while titanium is not
false, titanium is corrosion resistant and aluminum is not
61
what are the applications of centri in biological sciences?
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

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