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core practicals Flashcards

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1
Q

investigating the initial rate of reaction summary

A
  • 5 different enzyme concentrations
  • same volume in enzyme and substrate, mix together
  • zero the colourimeter with a distilled water cuvette to zero then measure absorbance straight away for initial rate
  • measure every 15s for 5 mins until absorbance stays the same
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2
Q

controls and data analysis - initial rate of reaction

A
  • concentration, same enzyme/substrate, temperature, ph, use regular intervals
  • repeat three times, use a control with water
  • plot an absorbance graph against time, then graph with rate of reaction over concentration
  • rate of reaction = Y/X to 2sf
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3
Q

using a micrometer

A
  • measure cell length with eyepiece graticule
  • calibrate with stage micrometer
  • count how many eyepiece graticule units are in each division of the micrometer (should be 100um)
  • micrometer / eyepiece to work out the value of 1 eyepiece unit eg 25um
  • count how many eyepiece units the cell occupies and multiply
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4
Q

using a light microscope to observe and measure biological samples (xylem and phloem) summary

A
  • place eyepiece graticule in lens and put the micrometer slide on the microscope stage
  • collect plant stem, add a few drops of water and use a sharp wet razor for a thin slice
  • add toludine blue dye, remove excess and use coverslip
  • superimpose graticule over micrometer
  • draw a biological drawing (no shading clear labels)
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5
Q

using a microscope

A
  • locate specimen on low power lens - objective lens
  • focus with course focus
  • move to medium and high power lens
  • use fine focus to focus
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6
Q

observing mitosis in root tips - summary

A
  • place hydrochloric acid into a 55c water bath for 15 mins, then place roots in acid for 5 mins
  • rinse in water and cut 0.5-1cm off the meristem and place in a vial of acetic orcein for 5 mins
  • tease apart on slide with mounted needle for single layer, root tip squash
  • examine under microscope
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7
Q

controls and data analysis - root tip squash

A
  • identify cells from low to high power
  • mitotic index: cells in mitosis / total cells for %
  • control ph, temp, time in acid/stain, length of tip, species
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8
Q

effect of sucrose concentration on pollen tube growth - summary

A
  • serial dilution of 2M sucrose: 1cm3 of solution to 9cm3 water , then 1cm new solution to 9cm3 water to get 2M, 0.2, 0.02, 0.002m ETC
  • add equal volumes of mineral salt medium
  • prep 5 petri dishes with water soaked filter paper (pevents drying)
  • place drop of sucrose onto petri dish then dust pollen on top
  • measure tube length with eyepiece graticule
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9
Q

data analysis - pollen tube growth

A
  • mean pollen tube growth / time
  • plot graph
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10
Q

the effect of temperature on membrane permeability - summary

A
  • water baths from 0-80c and put 10cm water in test tubes to acclimitise for 10mins
  • cut 1cm thick cyclinders with cork borers and remover and dry excess pigment
  • beetroot into test tubes for 10 mins
  • use cuvette with blue/green filter so red light is reflected, record absorbance
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11
Q

how does ethanol affect membrane permeability

A
  • breaks down cell membrane and bi-layer
  • small to large gaps appear to make membrane more leaky
  • denatures to suddenly increase permeability
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12
Q

investigating plant and water relations - plasmolysis summary

A
  • serial dilution of salt/sugar solutions for 5 concs
  • label 6 watch glasses to concentration
  • take 6 1-cell thick plant tissue samples of 1cm2
  • drop solution onto each slide
  • place tissure onto drop, leave for 20mins for osmosis
  • coverslip, how many /25 plasmolysed
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13
Q

incipient plasmolysis

A

when the membrane of the vacuole just starts to pull away from the cell wall - difficult to see
therefore dv is when 50% of cells are plasmolysed (shrivelled)

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14
Q

data analysis and controls - plant water relations

A
  • calculate percentage and mean
  • graph of plasmolysis against concentration and line of best fit
  • control with pure water
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15
Q

investigating an insects gas exchange system - summary

A
  • examine live body parts
  • dead locust
  • cut off the wings, pin to the board through the joints of the second pair of legs and tip of the abdomen
  • cut along the sides from tip to behind the antennae
  • flood with water to highlight silvery trachea threads
  • microscope and hand lens to examine trachea
  • cut around spiracles, discard and add water to reexamine
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16
Q

ethics of investigating insects

A
  • handle with care
  • fair sized container, separate live from dead
    -if investigating breathing, allow to return to normal
17
Q

investigate the effect of wind speed (or any others) on water uptake summary

A
  • place potometer in water, cut shoot underwater at an angle to avoid air bubbles, fix rubber tubing
  • take out of the water, apply vaseline and dry leaves and leave for 10 mins to acclimatise
  • insert a small air bubble and use a 3-way tap for a start point, measure distance moved by bubble over 5 mins
  • wind: fan should be 1m away, repeat each time with fan coming closer
18
Q

measuring -ometer rates

A

volume = pi x R2 x distance
rate = volume divided by time

19
Q

factors affecting the rate of aerobic respiration using a respirometer summary

A
  • assemble respirometer by separating organism from soda lime to absorb co2, place coloured dye in capillary tube and mark start position, close tap
  • mark difference moved every min for 5 mins (moves to organism)
20
Q

measuring respiration rate

A
  • 02 comsumption = distance moved / time taken
  • volume = pi r2 x distance
  • divide by mins for respiration per min
  • divide by mass for per gram
21
Q

controls for respirometers

A
  • use plastic beads
  • control/change temp, humidity, o2/co2 concentration
  • respiring seeds must be in the dark to prevent photosynthesis (produces 02)
22
Q

wavelengths of light on the rate of photosynthesis summary

A
  • cut pondweed and leave to photosynthesise for 5 mins so bubbles collect at photosynthometer then place in larger beaker
  • cover one side with foil, add 1/2 spatula of hydrogen carbonate to beaker so co2 for photosynthesis
  • place plastic filter over light and move 50cm away
  • calculate rate that bubble moves
23
Q

controls and analysis for light wavelength on photosynthesis

A
  • white light for control
  • lamp must be far enough away to control temp
  • calculate volume / time for rate of 02 output
24
Q

the presence of choroplast pigments using chromatography - summary

A
  • pencil line 2cm above end of chromo paper
  • grind plant leaves using pestle mortar and propanone
  • pipette small drops onto paper line, let dry and build up layers
  • place in test tube and in 1cm of petroleum spirit and cover with bung
  • leave until almost at the top
  • divide distance moved by each sport by distance the solvent moved for Rf
  • compare in a table
25
Q

controls and safety for chromatography

A
  • temp, ph, amount and species of plant
  • use safety goggles and well ventilated room
26
Q

rate of bacteria growth in liquid culture summary

A
  • use aseptic technique
  • prepare temp, food source, nutrients, antibiotic etc
  • flame bottle neck and innoculating loop, place is culture vessel then dip in broth, then flame again
  • pour broth without bacteria as a calibrator
  • incubate at 25c
  • measure absorbance 5 times over 24hrs
27
Q

analysis for bacteria growth in a liquid culture

A
  • plot a graph of absorbance over time
  • exponential growth rate
  • use a salibration curve for estimate from tubidity as not a direct count
28
Q

isolating an individual species from a mixed culture using streak plating - summary

A
  • aseptic technique
  • only have lid slightly raised to protect
  • 3 parallel streaks, turn and make 12 total, ensure they dont touch
  • flame, then place tape in x shape, allow some 02 entry
  • incubate 25c 24hrs
  • same technique, transfer each colony to separate plates
29
Q

effect of giberellin on production of amylase in germinating cereals using starch agar assay - summary

A
  • make a serial dilution of 1cm3 of 10^-3M to 9cm water and repeat 3 times up to 10^-6M
  • rinse 20 seeds/grains, peel husks and cut 1/2 lengthways
  • discard side with embryo - produces GA
  • soak 4 seed halves in each conc of GA, then 4 in distilled water for 24hrs
  • rinse in mild bleach to stop fungi growth, dry and push halves into agar
  • 24hr incubation then flood with iodine solution
  • starch prduction = blue/black
30
Q

controls and analysis for giberellin and amylase production

A
  • mean clear zone = pi x R2
  • plot scatter graph
  • GA produces amylase to digest starch as a food store - is the work of the endosperm
  • control using distilled water
  • side with embryo already produces giberellins/starch
31
Q

how to estimate population size with grids

A

mean density per quadrant X total area
/
area of each quadrat

32
Q

the effect of dif sampling methods on estimating population size - summary

A
  • choose area to study (e.g 10 x 10m) and divide into grids and allocate a number to each grid
  • random number generator to place quadrat into
  • calulate % cover - no of hits/no of availible x 100
  • as a point quadrat - record the number of grid intersections that the plant is found
33
Q

controls and analysis for different sampling methods

A
  • ovoid edge effect - only count plants that cross the top and left side of quadrat
  • calculate density = area x 4
  • use a t test to calc any sig differences between counts
34
Q

the effect of light/ abiotic factor on the distribution of a species

A
  • belt transect, place a quadrat along a 20m tape measure from no light to full light (or variable)
  • calc % cover of species and measure light/ factor with a meter
  • repeat every 2 m

biology (12 decks)

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