core practicals Flashcards
investigating the initial rate of reaction summary
- 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
controls and data analysis - initial rate of reaction
- 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
using a micrometer
- 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
using a light microscope to observe and measure biological samples (xylem and phloem) summary
- 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)
using a microscope
- locate specimen on low power lens - objective lens
- focus with course focus
- move to medium and high power lens
- use fine focus to focus
observing mitosis in root tips - summary
- 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
controls and data analysis - root tip squash
- 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
effect of sucrose concentration on pollen tube growth - summary
- 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
data analysis - pollen tube growth
- mean pollen tube growth / time
- plot graph
the effect of temperature on membrane permeability - summary
- 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
how does ethanol affect membrane permeability
- breaks down cell membrane and bi-layer
- small to large gaps appear to make membrane more leaky
- denatures to suddenly increase permeability
investigating plant and water relations - plasmolysis summary
- 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
incipient plasmolysis
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)
data analysis and controls - plant water relations
- calculate percentage and mean
- graph of plasmolysis against concentration and line of best fit
- control with pure water
investigating an insects gas exchange system - summary
- 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
ethics of investigating insects
- handle with care
- fair sized container, separate live from dead
-if investigating breathing, allow to return to normal
investigate the effect of wind speed (or any others) on water uptake summary
- 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
measuring -ometer rates
volume = pi x R2 x distance
rate = volume divided by time
factors affecting the rate of aerobic respiration using a respirometer summary
- 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)
measuring respiration rate
- 02 comsumption = distance moved / time taken
- volume = pi r2 x distance
- divide by mins for respiration per min
- divide by mass for per gram
controls for respirometers
- use plastic beads
- control/change temp, humidity, o2/co2 concentration
- respiring seeds must be in the dark to prevent photosynthesis (produces 02)
wavelengths of light on the rate of photosynthesis summary
- 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
controls and analysis for light wavelength on photosynthesis
- white light for control
- lamp must be far enough away to control temp
- calculate volume / time for rate of 02 output
the presence of choroplast pigments using chromatography - summary
- 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
controls and safety for chromatography
- temp, ph, amount and species of plant
- use safety goggles and well ventilated room
rate of bacteria growth in liquid culture summary
- 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
analysis for bacteria growth in a liquid culture
- plot a graph of absorbance over time
- exponential growth rate
- use a salibration curve for estimate from tubidity as not a direct count
isolating an individual species from a mixed culture using streak plating - summary
- 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
effect of giberellin on production of amylase in germinating cereals using starch agar assay - summary
- 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
controls and analysis for giberellin and amylase production
- 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
how to estimate population size with grids
mean density per quadrant X total area
/
area of each quadrat
the effect of dif sampling methods on estimating population size - summary
- 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
controls and analysis for different sampling methods
- 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
the effect of light/ abiotic factor on the distribution of a species
- 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
