Biology Booklet 2 revision

• Making onion slides on microscopes

  1. Forceps are used to peel the thin, transparent epeidermis cell from a section of onion
  2. The epidermis is then placed on slide with a few drops of iodine solution or methylene blue, these chemicals colour the cells to make it more obvious
  3. A coverslip is lowered onto the slide using forceps, try not to trap any air bubbles. The coverslip will protect the lens of the microscope and prevent the cell from drying out
  4. It is then placed onto the stage
  5. Observe the cells, starting at a low power then getting higher power lenses
• Destarching a leaf

  1. Place the leaves into the dark for at least 2 days
  2. This ensures any starch has been used by the plant cells
  3. This ensures the results from the starch test are reliable
• The starch test

  1. A leaf is removed from a plant that has been in bright light and is placed in boiling water for 30 seconds to kill the leaf.
  2. The leaf is then placed in boiling ethanol, in a water bath as ethanol is flammable. The ethanol removes the chlorophyll, making the leaf a whitish-green colour and brittle.
  3. The leaf is dipped into water to soften it
  4. The soft leaf can be spread on a white tile and iodine solution is added
  5. If starch is present, it will turn from yellow-brown to blue-black
• Light in photosynthesis

  1. Destarch a plant
  2. Test a leaf from the destarched plant for the presence of starch and if it tests negative continue to 3 and if it doesn't, continue to destarch it.
  3. Cover a part of one leaf of the plant with foil. Make a drawing of the leaf at the start of the experiment
  4. Place the plant in bright light for several hours
  5. Test the leaf from the plant for starch.
• Chlorophyll in photosynthesis

  1. Destarch a variegated plant
  2. Test a leaf from the destarched plant for starch and if it is negative, continue to step 3
  3. Make a drawing of one of the leaves
  4. Place the plant in bright light for several hours
  5. Test the leaf from the plant for starch
  6. Draw the leaf afterwards

  
• Food tests

  Sugar - Benedict's test - Add Benedict's solution to the food and heat in a water bath - It changes from blue to green then orange to brick red precipitate, depending on how much sugar is presesnt

  Protein- biuret test- Add sodium hydroxide to the food solution the copper sulfate and shake - the mixture changes from blue to purple

  Fats - ethanol - mix the fat with ethanol to dissolve some of it then add to water - it changes from clear to a white emulsion
• Investigating the energy content of food by burning samples

  1. The food is held on the edge of a safety needle (Dont use nuts), ignited
  2. placed underneath the test tube.
  3. The rise in the temperature of the water will indicate the amount of energy in the food

  It is calculated using the formula : mass of water x rise in water temperature x 4.2

  To calculate joules per grams, use the formula, energy released/ mass of food sample

  
• Investigating the effect of temperature on the enzyme action

  1. Set up five water baths at 10,20...
  2. Label 5 test tubes with starch and the temperature
  3. Label five test tubes amylase and the temperature o
  4. Use a syringe to measure 5cm^3 of 1% starch solution into each of the test tubes labelled starch
  5. Repeat with the amylase solution
• Investigating the effect of temperature on enzyme action

  6.Place one starch and one amylase test tube in each water bath for five minutes

  7.Prepare a spotting tile for each of the temperatures by placing one drop of iodine solution in each dimple

  8.Pour the amylase solution into the starch solution. Use a clean dropping pipette to sample the mixed solution and time

  9.Add one drop of the sample of iodine solution in the first dimple

  10. Repeat the sampling every minute until the iodine shows no colour change and record time

  Repeat
• Using quadrats to investigate abundance

  1. place two 20m measuring tapes at right angles to each other to mark out the area of grassland to be sampled
  2. Use random numbers to select five sets of coordinates
  3. Place a 1m^2 quadrat at each coordinate and count the number of daisies etc...
  4. Calculate the average
• Investigating species between high and low tide using a belt transect

  *Be careful as rocks can be slippery

  1. Extend a measuring tape as a transect from high tide mark down to the low tide mark
  2. Place a quadrats (0.5m) beside the tape at the 0-0.5m measurent. Record the position of the quadrat
  3. Identify the organism
  4. Repeat steps 2 and 3 with quadrats placed at regular intervals down the transect tape until the full length has been sampled
  5. Draw a bar graph
• Osmosis, using potatoes

  1. You will be given a range of sucrose solutions at different concentrations
  2. Set up and label the number of beakers with their concentrations
  3. Using a cork borer, cut up five potato cylinders
  4. Weigh each cylinder and add one to each beaker
  5. Leave for an hour
  6. Pat dry and reweigh the potato cylinders
• Osmosis using visking tubing

  1. Add 5% sucrose solution to visking tubing, ensuring the tubing is tied securely at each end
  2. Dry the outside of the tubing if necessary and weigh the tubing
  3. Add the visking tubing to a beaker of water for at least 1 hour
  4. Pat dry the outside of the visking tubing and reweigh
• Using a potometer, investigate the factors affecting the rate of water uptake

  1. Set up a bubble potometer by attaching a shoot to the neck of the apparatus. Take the precautions to prevent air leaks such as setting the potometer up underwater
  2. Calculate the rate of movement of the bubble over time for a particular condition such as windy
  3. Repeat to gain more reliable results
  4. Adjust the conditions, for example, a plastic bag to create humid levels
  5. Repeat
• Using the washing line method

  1. Destarch six leaves
  2. Smear petroleum jelly over the cut stalks to make them waterproof
  3. Measure the mass of each leaf and then using paper clips, hang them on a line of string suspended between two retort stands
  4. Suspend half the leaves on a line of string at a high temperature and the other half at a lower temperature to investigate the effect of temperature
  5. After 24 hours, reweigh the leaves and calculate the average
• Investigating the need for carbon dioxide

  1. Compare two leaves
  2. use sodium hydroxide to absorb the carbon dioxide from the experimental leaf
  3. The control will leaf will only have water in its flask
• Investigating the rate of photosynthesis

  1. This is through observing the oxygen
  2. The rate is accurately calculated by measuring the volume of oxygen produced after five minutes.
  3. or an oxygen electrode connected to a data logger can be used to measure the change
• Hydrogencarbonate indicator

  Red - yellow = carbon dioxide

  Red - purple = decrease
• Aseptic techniques

  • Not eating or drinking in the lab
  • Wiping down lab benches with disinfectant
  • Not culturing microbes at body temperatures
  • Using sterile loops to transfer cultures
  • Flaming the necks of culture bottles to prevent contamination
  • Sterilising (autoclave) or disposing of all equipment after use
  • Wash hands thoroughly after each part of the experiment