Bio Practicals Flashcards

1
Q

What does haemocytometry measure?

A

Total cell count

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2
Q

Preparation of a haemocytometry plate

A
  • Well mixed cell culture sample is first diluted
  • Then introduced to the central chamber via pipette
  • Liquid flows under cover slip
  • Sample viewed under microscope and no. of organisms in several squares is counted
  • Average is calculated, multiplied by dilution factor gets you an estimate of the original number in the sample
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3
Q

Turbidimetry measures

A

Total cell count

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4
Q

Turbidimetry is measured using

A

Colorimeter

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5
Q

Turbidmetry preparation

A
  • Culture sample is aseptically removed and thoroughly mixed before being placed in a cuvette.
  • Cuvette is placed in the colorimeter and the optical density is measured as % absorbance.
  • More cells present = greater turbidity
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6
Q

Cons of turbidmetry

A

Cannot distinguish living cells from dead cells

Cannot distinguish cells from particles of matter in the culture medium

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7
Q

To avoid inaccuracy created by particles of matter from the medium affecting the percentage absorbance, what precaution is taken?

A

Colorimeter is set to zero using a ‘blank’ cuvette which contains the culture medium alone

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8
Q

What does dilution plating measure

A

Viable counts

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9
Q

Methods of sterilisation

A
  • Direct heat - inoculating loop, neck of tubes
  • Autoclaving (120) - glassware, unwanted cultures
  • Burning alcohol - quick sterilisation of glass
  • Disinfectants - inanimate objects, e.g. Wood surfaces
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10
Q

Bioassay

A

Enables the effectiveness of a compound (antibiotic or disinfectant) to be determined by its effect on the growth of a microorganism

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11
Q

What can bioassays be used to screen and how

A

Microorganisms to determine if they produce an effective antibiotic.
Achieved by measuring their ability to inhibit the growth of bacteria on a bacterial lawn.

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12
Q

What does the diameter increase of a fungal mycelium measure?

A

Growth of filamentous fungi

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13
Q

Increase in dry mass measures

A

Growth rate of a variety of microorganisms

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14
Q

Problems with ORS containing more glucose

A

Lowered the water potential in the lumen of the small intestine cause diarrhoea to worsen

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15
Q

What polysaccharide is present in ORS and why

A

Starch as it is osmotically inactive and insoluble
It also is slowly broken down by amylase and maltose into glucose
This mean it can be taken up by co-transport at a normal rate

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16
Q

Ideal scientific trial for medicines

A
  • Large sample size
  • Random split of subjects into two groups
  • One group receives medicine, the other a placebo
  • Mean results compared
17
Q

Medical testing with ORS

A
  • sample must all suffer from diarrhoea
  • Subjects are typically children at risk of death
  • It is unethical and unacceptable to conduct trials ‘scientifically’