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AS Biology Core Practicals, Daphnia are invertebrates, are transparent so…
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Daphnia are invertebrates, are transparent so their heartbeats can be observed
1) Use different concentrations of caffeine solution & one control of distilled water 2) Place the daphnia on the cavity slide and place cotton cool under it (prevents it from moving too much) 3) With a pipette drop caffeine solution on the daphnia & place under a light microscope
4) Using a stopwatch count the nbr of heart beats in 20secs 5) Repeat with the diff solutions & water
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1) Measure a set volume of DCPIP at at a set conc in a test tube
2) Through titration, add a Vitamin C solution(fruit juice)drop by drop by a pipette
3) Swirl the tube & once the solution turns colourless record the volume of Vitamin C used to do so
4) Repeat twice more with the same solution & Repeat with the other fruit juices
1) Cut a root tip with a scalpel (area where mitosis is occurring)
2) Add the root tip to HCl in a test tube in a water bath for 5mins
3) Transfer it to cold water & dry it
4) Place the root tip on a slide & spread cells with a needle
5) Add the orcein ethanoic stain & place a cover slip to squash cells
6) Place under a light microscope & observe
Tensile strength is the maximum load a fibre can hold before it breaks, important for use of it e.g. ropes
1) Separate the fibres using forceps
2) Add a fibre to a clamp stand & weights to the other end
3) Keep adding weights until the fibre breaks
4) Repeat with diff samples of same fibre e.g. internal/external to get mean
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- Disinfect surfaces to prevent contamination
- Close the windows & doors to limit air currents
- Work with a Bunsen burner so the hot air currents rising can draw away the microbes
- Flame the necks of bottles & wires so no unwanted microorganisms are present
1) Prepare an agar plate (has agar jelly) by pipetting bacteria & spread with a spreader.
2) Grind the plant & soak in alcohol (extracts the antimicrobial properties)
3) With sterile forceps place the discs in the plant for the same time
4) Place the discs & control disk (that only absorbed ethanol) into agar plate & tape the lid on (less O2 forming more anaerobic bacteria) to incubate at 25degree for 24hrs (so the bacteria can grow well enough)
5) The clear zones will show the antimicrobial activities & measure the diameter to work out the area by pi x r2
The more permeable a membrane, the more pigment will leak out
1) Use a cork borer to cut identical cylinders of beetroot & rinse to remove any pigment on it (that could affect results)
2) In test tubes measure equal amounts of water with beetroot & place into water baths of diff temperatures, leave for 15mins
3) Remove the beetroot pieces & set up a colorimeter at a blue filter
4) With a pipette transfer the liquid into the cuvette (plastic placed into colorimeter) to record the absorbance & repeat for the others
- As alcohol conc increases = permeability increases - As the alcohol dissolves lipids making membrane lose its structure
- As temp increases = permeabilty increases - As phospholipids arent packed and can move with more energy, the proteins denature breaking the bonds & the structure
Measuring how fast a product forms
- Add hydrogen peroxide at a set volume & conc to a boiling tube & add a buffer(maintains pH)
- Using a pipette add a set volume of one of the concentrations of catalase & attach the bung
- Record how much oxygen formed in measuring cylinder with a stopwatch
- Repeat with same conc & with the conc of catalase (shows change in the enzymes concetration)