Practicals Flashcards

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1
Q

Why was a root tip and stain used, and why was the root firmly squashed (RQ2 - mitosis)?

A

Root tip: Where mitosis occurs
Stain: To distinguish chromosomes
Squashed: Thin layer to allow light through

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2
Q

What is the equation for calculating how long cells spent in one stage of mitosis (RQ2)?

A

number of cells in that stage/total number of cells) x time taken for 1 cell cycle

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3
Q

What is the equation for calculating mitotic index (RQ2)?

A

number of cells in mitosis/total number of cells

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4
Q

How is the length of a cell estimated using an optical microscope (RQ2)?

A

Measure length with eyepiece graticule and calibrate against stage micrometer of known length

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5
Q

How can a results table be used to find the water potential of plant tissue (RQ3)?

A
  1. Plot graph with conc. on x-axis and % change in mass on y-axis
  2. Find conc. where curve crosses x-axis
  3. Use another resource to find water potential where curve crosses x-axis
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6
Q

Why is the tissue cut into discs and blotted dry before weighing (RQ3 - water potential)?

A

Discs: Increases surface area for osmosis
Blotted dry: Solution would add to mass of discs which would vary results, giving inaccurate change in mass

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7
Q

What are the reasons for differing results with the same procedure (RQ4 - membrane permeability)?

A

Variation in beetroot or judgement of colour

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8
Q

Why does the amount of colour in the solution increase as concentration of alcohol increases (RQ4 - membrane permeability)?

A

Phospholipids in membranes dissolve in alcohol so membranes break down faster which allows faster rate of diffusion of pigments so more pigments move out of cells

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9
Q

What precautions should be taken when carrying out a dissection (RQ5)?

A

Take care with scalpel when cutting tissue by not cutting towards hand, use gloves, disinfect bench, safely dispose of sample

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10
Q

Why is working in close proximity to a Bunsen burner important (RQ6 - effect of aseptic technique on microbial growth)

A

Creates convection current that causes bacteria to rise up away from plate so bacteria doesn’t contaminate plate

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11
Q

Why is flaming the neck of the bottle containing E.coli culture important (RQ6 - effect of aseptic technique on microbial growth)?

A

Kills any other bacteria which may be on bottle so sterile pipette used to collect bacteria isn’t contaminated

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12
Q

Why is only slightly raising the lid of the Petri dish important (RQ6 - effect of aseptic technique on microbial growth)?

A

Avoids any bacteria in the air contaminating Petri dish

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13
Q

Why is dipping the glass spreader in alcohol and flaming it before and after use important (RQ6 - effect of aseptic technique on microbial growth)?

A

Sterilises the spreader

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14
Q

Why is leaving the spreader to cool before spreading the liquid over the surface of the agar important (RQ6 - effect of aseptic technique on microbial growth)?

A

Doesn’t kill bacteria on the plate that you want to grow and investigate

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15
Q

Why is securing the lid of the Petri dish with 2 pieces of tape important (RQ6 - effect of aseptic technique on microbial growth)?

A

Allows O2 to get in so bacteria can respire to produce ATP needed in growth/replication

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16
Q

Why is incubating the Petri dish at 30°C rather than optimum 37°C important (RQ6 - effect of aseptic technique on microbial growth)?

A

Bacteria will grow too quickly if grown at too high temps which can encourage growth of resistant bacteria

17
Q

How should equipment be treated after the experiment and why (RQ6 - effect of aseptic technique on microbial growth)?

A

In an autoclave, uses high temps and pressure to kill bacteria and sterilise equipment