core practicals Flashcards
devise a practical to Investigate the effect of caffeine on the heart rate of Daphnia
Remove 1 Daphnia with a pipette and place it in a cavity slide under a microscope.
Dab around the Daphnia with a tissue to remove the pond water and replace with drops of caffeine solution (e.g. 0.1M).
Leave the Daphnia for 5 minutes to acclimatise and then observe & count (using a counter) the heart rate under the microscope for 30 seconds (multiply number by 2 to calculate beats per minute).
Repeat this for measurements across 5 different caffeine concentrations (e.g. 0.2M, 0.3M, 0.4M and 0.5M). Repeats can then be carried out with two other Daphnia.
devise an investigation to investigate and compare the antimicrobial properties of garlic and mint.
Pipette 0.1 cm³ of the garlic extract solution onto 4 of the sterile paper discs. Allow each disc to dry. Repeat this process for the mint extract solution.
Label the other Petri dishes for garlic, mint and control solutions – include the date.
Use the sterile forceps to place all 4 discs of each type of extract onto their corresponding Petri dish.
Close each dish and seal with hazard tape. Make sure that a small gap is left so that oxygen can enter and there is no build-up of anaerobic bacteria.
Leave the cultures to incubate overnight.
Open each Petri dish and use a ruler to work out the zone of inhibition for each paper disc.
devise an investigation to To investigate the effect of plant mineral deficiencies on plant growth.
Half fill a test tube with the solution containing all nutrients.
Cover the top of the tube with aluminium foil and push down on covering so that there is a well in the centre.
Gently push the roots of Mexican Hat plantlet through the hole so it is in the solution below.
Repeat steps 1 to 3 with the other 4 solutions.
Wrap all tubes in aluminium foil and place them in the test tube rack on a sunny window sill.
Leave plantlets for approximately one week.
Observe characteristics and growth of the plantlets, comparing each solutions’ effects.
devise an investigate the vitamin C content in different fruit juices.
Pipette 1cm³ of 1% blue DCPIP into a test tube.
Use an accurate pipette to add 1-3 drops of the first fruit juice to the same test tube and then shake the mixture 3 times. Continue to add drops and shake the contents of the test tube until the blue colour of the DCPIP disappears.
Note down the volume of fruit juice that was used up.
Repeat this procedure for the other fruit juices available.
Repeats can be carried out 2 times to get mean results.
devise an experiment To investigate membrane structure, including the effect of temperature on membrane permeability.
Use a cork borer and knife to cut 8 x 1cm lengthed cylinders of beetroot over a white tile.
Place all the cut pieces in a beaker of distilled water and leave overnight to remove any dye (betalains) released when the beetroot was cut.
Wash and blot dry (with filter paper or a tissue) the 8 pieces of beetroot.
Fill 8 boiling tubes each with 10cm³ of distilled water and place them into 8 separate water baths of different temperatures (e.g. 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C).
Once at the desired temperature, add a piece of beetroot to each boiling tube and leave for 30 minutes.
Remove the beetroot pieces gently with a pair of forceps and then shake the tubes to disperse the dye.
Set a colorimeter to percentage absorbance on the blue/green filter.
Calibrate by filling a cuvette with distilled water first then add 2cm³ of beetroot solution from the first temperature to a new cuvette.
Place this cuvette into the colorimeter to read the percentage absorbance. Repeat this for all other pieces.
describe an experiment To determine the tensile strength of plant fibres.
The plant material should be left to soak in a bucket of water for about a week in order for the fibres to be easily extracted (retting).
Once the fibres have been removed, connect them between 2 clamp stands and gradually add mass in the middle until the fibre snaps.
Note the mass required to snap the fibre.
Try this again but with individual fibres from different plants and different ways of combining fibres (e.g. twists). You can also compare the tensile strength of the stem to the individual fibres.
devise an experiment To investigate the effect of temperature on the initial rate of an enzyme-catalysed reaction
Set up the water baths at 10°C, 20°C, 30°C, 40°C and 50°C and put a beaker of lipase, containing a 2 cm3 syringe into each water bath.
Label a test tube with the temperature to be investigated.
Add 5 drops of phenolphthalein to the test tube.
Measure out 5 cm3 of milk using a measuring cylinder and add this to the test tube.
Measure out 7 cm3 of sodium carbonate solution using another measuring cylinder and add this to the test tube. The solution should be pink.
Place a thermometer in the test tube. Take care as the equipment could topple over.
Place the test tube in a water bath and leave until the contents reach the same temperature as the water bath.
Remove the thermometer from the test tube and replace it with a glass rod.
Use the 2 cm3 syringe to measure out 1 cm3 of lipase from the beaker in the water bath for the temperature you are investigating.
Add the lipase to the test tube and start the stopwatch.
Stir the contents of the test tube until the solution loses its pink colour. Stop the watch and note the time in a suitable table of results.
