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MBB265 > General/Last year > Flashcards

General/Last year Flashcards

1
Q

What is % (w/v)?

A
  • g/100ml
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2
Q

What is M?

A
  • mol/l
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3
Q

What is accuracy?

A
  • whether all values are close to true value
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4
Q

What is consistency (precision)?

A
  • whether all values are close to each other
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5
Q

Why would you dilate bacteria in saline rather than water?

A
  • saline has same Ψ as bacterial cells

- pure water would cause water to enter cells and burst

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6
Q

What is the difference between viable cell count and total cell count?

A
  • viable is actively growing cells

- total inc dead cells

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7
Q

What is a streak plate culture and what does it allow?

A
  • cooled medium poured into petri dish and allowed to set in smooth even layer
  • inoculum streaked onto surface of medium to prod well separated colonies after incubation
  • allows cells to be spread more evenly , so individual colonies can be isolated
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8
Q

What is a spread plate culture?

A
  • plate prepared like streak
  • inoculum is drop of liquid bacterial culture
  • transferred w/ pipette and spread using spreader dipped in alcohol and passed through bunsen flame (sterilising it)
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9
Q

What is a pour plate culture, and when is it a useful technique?

A
  • inoculum added to melted and cooled agar medium
  • gently mixed and poured into plates
  • or inoculum placed into petri dish and liquid medium added
  • to ensure even distribution, moved w/ rotating movement
  • useful for isolation of bacterial cultures from mixed inoculum, or where heavy even growth needed
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10
Q

What is an overlay culture?

A
  • similar to pour plates
  • inoculum mixed w/ smaller amount of melted agar medium
  • poured in thin layer to solidify on top of solid medium already in petri dish
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11
Q

What are stages of a gram stain?

A
  • heat fixed smear
  • stain w/ methyl violet
  • iodine to trap stain in peptidoglycan layer
  • ethanol wash
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12
Q

What do the results of a gram stain indicate about whether cells are gram +ve or -ve?

A
  • +ve = purple

- -ve = pink/red

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13
Q

What is the difference between gram +ve and gram -ve cells?

A
  • gram +ve have thick cell wall, so retains methyl violet

- gram -ve have thin cell wall

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14
Q

What does G banding do?

A
  • stains gene-poor, heterochromatic regions
  • leaving transcriptionally active regions unstained
  • generates specific banding pattern for each chromosome
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15
Q

Would you expect standard curve for spectrophotometer to be linear and how long for?

A
  • in theory always linear
  • in practise it wouldn’t, as machine can’t accurately measure v small amount of light being transmitted
  • compound becomes more conc, will reach point where no longer be soluble
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16
Q

What does absorbance equal?

A
  • A = ECt
  • E is extinction coefficient
  • C is conc
  • t is path length
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17
Q

How is pH calculated from [H+]?

A
  • -log[H+]
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18
Q

What is the equation for Ka?

A
  • Ka = [H+][A-] / [HA]
19
Q

What is the Henderson-Hasselbalch equation?

A
  • pH = pKa + log( [A-] / [HA] )
20
Q

How is pKa calculated from [Ka]?

A
  • -log[Ka]
21
Q

What is the relationship between pH and pKa when [A-] = [HA]?

A
  • pH = pKa
22
Q

What are the limitations of Lineweaver-Burk plot?

A
  • difficult to find x-intercept as never any minus values
  • bunching of lower values relied on to draw line to bigger values
  • larger values unreliable as at low substrate conc
23
Q

What is an autoclave?

A
  • strong heated container used to sterilise equipment by subjecting them to high pressure steam at 138kPa, heated to 121º for 20 mins
24
Q

How can optical density be used to measure bacterial growth?

A
  • cells in suspension scatter light
  • only proportion of light passes through to be detected by photocell in spectrophotometer
  • as cell density increases w/ growth, more light scattered and optical density increases
25
Q

What features do plasmids used as vectors generally have?

A
  • contain origin of replication functional in E. coli
  • multiple restriction sites, which can be used to insert foreign DNA
  • encode gene for resistance for antibiotic as means of selection
  • relatively small and present at high copy no. per cell so can be purified in large amounts
26
Q

What % agarose gels do labs typically use and what can this resolve?

A
  • 1%

- can adequately resolve DNA fragments ~1-10kb

27
Q

What factors can proteins be purified by?

A
  • size
  • shape
  • charge
  • solubility
  • stability
  • binding specificity
28
Q

What is the formula for chi-squared?

A

Σ { (O-E)2 / E }

29
Q

How is dilution factor calculated?

A
  • total final vol / vol of original solution

- starting conc / final conc

30
Q

How is total dilution factor of serial dilutions calculated?

A
  • multiply individual dilution factors together
31
Q

What are doubling dilutions?

A
  • series of 2 fold dilutions
32
Q

What are the prefixes for the different powers of 10 from 6 to -15?

A
  • 6 = mega (M)
  • 3 = kilo (k)
  • 2 = hecto (h)
  • 1 = Deca (da)
  • -1 = deci (d)
  • -2 = centi (c)
  • -3 = milli (m)
  • -6 = micro (μ)
  • -9 = nano (n)
  • -12 = pico (p)
  • -15 = femto (f)
33
Q

How can volumes in L be converted to volumes in m^3?

A
  • 1L = 1dm^3
  • 1ml = 1cm^3
  • 1μl = 1mm^3
34
Q

How do you calculate standard deviation?

A
  • √ of Σ {(x – x)^2} / (n-1)
35
Q

How is density calc?

A
  • mass / vol
36
Q

What is the density of water?

A
  • 1g/mol
37
Q

What is the mass of 1 mol C-12?

A
  • 12g
38
Q

What does Avogadro’s no. tell you?

A
  • = no. units in a mole

- = atoms of 12C in 12g of 12C

39
Q

What equation can be done if you know a vol and 2 concs (or a conc and 2 vols)?

A
  • c1v1 = c2v2
40
Q

How do you get ATP/EGTA/EDTA to dissolve in water?

A
  • pH will drop to 3 –> stirring and heating will have no effect
  • titrate w/ base to neutralise and dissolve acid, then correct to req pH after dissolved
41
Q

When should serial dilutions be carried out, and why?

A
  • when adding v small vols to v large vols

- as error would be too large and mixing not even

42
Q

How do you calibrate a pH meter?

A
  • remove cap and rinse in distilled water
  • switch on (slide to right)
  • calibrate in pH7 buffer and wait for it to settle
  • take small screwdriver and adjust top left screw (ACW to decrease reading)
  • calibrate in pH4 or 9.2 (whichever brackets pH aiming for)
  • adjust right hand screw
  • rinse w/ distilled water
43
Q

How do you make a solution of 250ml w/ 2 solid components?

A
  • weigh out and transfer to beakers
  • add <250ml (as solids contribute to vol and need to add acid and alkali to get to desired pH) –> about 200ml
  • put in magnetic stir bar
  • make to desired pH (acid to lower) add dropwise w/ pasteur pipette, w/ stirrer still in
  • rinse probe and replace cap
  • make up to 250ml w/ distilled water, by pouring all back into cylinder
  • mix in beaker
44
Q

What is the difference between technical and biological repeats?

A
  • technical repeats = repeated measurements of same sample –> look at measurement error w/ equipment etc.
  • biological repeats = repeating whole experiment to get biologically distinct samples –> look at random biological variation

MBB265 (3 decks)

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