Two core AS/A-Level Biology practicals are included. Both include a hypothesis (and null hypothesis), equipment list, method, the different variables, risk assessment, results table, graph, and concludes with an analysis and evaluation looking at systematic and random error. References are addition...
INVESTIGATING THE EFFECT OF TEMPERATURE ON
MEMBRANE STRUCTURE
HYPOTHESIS
I’m expecting that increased temperature will increase the membrane
permeability. As a result, the colour should become darker the higher the
temperature and therefore increase the percentage light absorbance.
NULL HYPOTHESIS
No significant difference in membrane permeability at different temperatures.
EQUIPMENT
- Raw beetroot
- Cork borer
- White tile , temperature
- Knife
- Ruler
- Water baths at different temperatures
- Plastic beaker
- Boiling tubes
- Boiling tube racks
- Ice
- Thermometers
- Colourimeter
- Cuvettes
- Stopwatch
- Distilled water
- Pipettes
- Measuring cylinders
- Sieve (results 90℃-0℃ left to right)
METHOD
1. Cut the top and bottom off the beetroot using a knife and, using the
same cork borer, cut 24 cylinders of beetroot. Precisely cut these
cylinders into identical 1cm long sections using a ruler.
2. Place the beetroot cylinders into a beaker of distilled water. Leave them
and then rinse to wash away excess dye.
3. Mix hot and cold water (or use ice) to prepare and maintain the water
baths at 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ and 90℃.
Fill 3 boiling tubes per water bath with 5 cm3 of distilled water and leave
them for 5 minutes in the water baths until they reach the required
temperature (measure this with a thermometer).
4. Once they reach the desired temperature, place a cylinder of beetroot in
each boiling tube. Leave for 30 minutes (time with a stopwatch and
ensure to maintain the water temperature in the baths).
, 5. Turn on and set the colourimeter to a blue/green filter, to read the %
light absorbance, and then calibrate it using a cuvette filled with distilled
water so that it reads 0%.
6. Remove the boiling tubes from the water baths and place them on a
boiling tube rack. Remove the beetroot from the boiling tubes and swirl
them to disperse the dye.
7. Using a pipette, transfer 2 cm3 of dye solution from each boiling tube
into their respective cuvettes. Place these cuvettes into the colourimeter
and record the reading for the % absorbency in a results table. Ensure
to recalibrate the colourimeter using the distilled water in between each
reading.
RISK ASSESSMENT
RISK HAZARD PRECAUTIONS
Knife Could cut skin or harm Wear eye protection and cut
others away from the body.
Broken glass Could cause harm Wear eye protection and be
careful when handling.
Hot water Could burn skin Be careful when handling. If
burns occur, run under cool
water for 20 minutes.
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