biology practicals

• how do you prepare your slide?

  1. add a drop of water to the middle of a clean slide
  2. cut an onion into layers and use tweezers to take off the bottom epidermal tissue
  3. use tweezers to place epidermal tissue into the water
  4. add iodine to highlight subcellular structures
  5. add cover slip by tilting and lowering but try not to get air bubbles or it'll obstruct the view
• how do you use a light microscope?

  1. clip slide to the stage
  2. select the lowest lens
  3. use coarse adjustment knob to bring the stage into view
  4. look into eyepiece and use coarse to adjust focus
  5. adjust the focus further using fine adjustment knob
  6. if you need a higher magnification use a higher lens
• practical on culturing microorganisms?

  1. hot agar jelly or nutrient broth solution poured into petri dish
  2. once cooled so bacteria aren't killed, use inoculating loop to transfer organisms to culture medium
  3. or use a sterile dropping pipette and spreader instead
• effect of antibiotics on bacterial growth?

  1. place paper discs soaked in different concentrations or antibiotics onto agar plate
  2. antibiotics should diffuse and non resistant strains should die leaving an inhibition zone
  3. use a control soaked in sterile water to ensure the only effect is due to the antibiotic itself
  4. leave at 25C for 48 hours
  5. TAPE, UPSIDE DOWN, STERILIZE.
• effect of sugar solutions on plant tissue?

  1. cut potato into identical cylinders
  2. measure initial mass with zero'd balance
  3. get beaker one with pure water the other with a high concentration of sugar solution e.g 1 mol/dm3
  4. leave for 24 hours take out and dry to ensure no left over mass
  5. calculate percentage change in mass
• practical on investigating enzymatic activity with pH?

  1. put drop of iodine into spotting tile wells
  2. set up bunsen burner on heat proof mat under tripod and gauze with a beaker of water
  3. heat the beaker to 35C ( can use a water bath to keep constant temperature) measure with a thermometer
  4. 1cm3 amylase and buffer solution with PH 5 by using syringe
  5. add 5cm3 of starch and start stopwatch
  6. use continuous sampling and repeat with higher PH of buffer solution
• how to prepare a food sample?

  1. use a pestle and mortar to ground up
  2. transfer to beaker with distilled water
  3. stir with glass rod to dissolve
  4. filter with funnel
• food test for sugarss?

  1. 5cm3 of food sample
  2. 75C water bath
  3. 10 drops of benedicts
  4. stir and wait 5 minutes
  5. blue-green-yellow-red
• food test for starch?

  1.5cm3 food sample into test tube

  2. add drops of iodine and gently shake

  3. orangey brown to blue black
• food test for lipids?

  1. prepare 5cm3 unfiltered food sample into test tube
  2. 3 drops of sudan III solution or ethanol and gently shake
  3. if present a red layer of lipid will seperate
• test for developing drugs?


  (after test of human and animal live cells to test for efficacy and toxicity)

  1. tested on healthy human volunteers to ensure no side effects
  2. low dose gradually increased
  3. optimum dose found to ensure minimum side effects and best dosage
  4. double blind trial with placebo
  5. peer review to prevent false claims
• investigating effect of exercise on the body?

  [ measure breathing rate by counting breaths and heart rate by taking pulse on wrist or neck]

  1. measure pulse after 5 minutes of sitting, walking, jogging and running
  2. the more vigorous the exercise the quicker pulse rate in order to increase oxygen to muscles and take off carbon dioxide from muscles
  3. to reduce random errors repeat as a group and plot average
• using quadrats and transects?

  [ QUADRATS- compare how common organisms are between 2 sample areas]

  1. place 1m2 quadrat at a random point within first sample area
  2. count organisms
  3. repeat and workout mean
  4. repeat in second sample area and compare

  [ TRANSECTS- compare distribution across an area]

  1. mark out a line using a tape measure
  2. collect data by counting or using quadrats
• investigating effect of temperature on lipase on decay?

  1. 5cm3 lipase using measuring cylinder into 'L' labelled test tube
  2. measure 5cm3 of milk and add to different test tube
  3. add 5 drops of phenolphthalein and 7cm3 of sodium carbonate turning it alkaline therefore pink
  4. leave both test tubes at 30C in water bath a d measure with thermometer
  5. use calibrated dropping pipette to add 1cm3 of lipase immediately start stopwatch
  6. stir with glass rod to decompose and measure end point via colour change
  7. repeat with different temperatures { RATE= 1000/t s-1}