Biology paper one

• Microscope-method

  1. Place a tissue sample on the microscope slide.

  2. Add a few drops of a suitable stain.

  3. Lower the coverslip onto the tissue.

  4. Place the slide on the microscope stage and focus on the cells using lower power.

  5. Change to high power and refocus.

  6. Draw any types of cells that can be seen.

  7. Add a scale line to the diagram.
• Stage


  Centre of the microscope where the slide is placed

  
• Lamp


  Provides the light needed to view the specimen

  
• Coarse focusing dial

  A dial used to change thee position of the objective lens by a large amount

  
• Fine focusing dial


  A dial used to change thee position of the objective lens by a small amount

  
• Microscope-notes

  -The scale line can be added by focusing on the millimetre devision of a ruler.

  -The drawings must be only what you can see and drawn with a pencil

  -Don't be looking through the eyepiece while adjusting the coarse focusing dial

  -Include a magnification scale on the drawing
• Culturing microorganisms-method


  1. Sterilise all equipment

  2. Open an agar plate near a bunser burner

  3. Use an inoculating loop to spread bacteria evenly across the agar

  4. Place antibiotic soaked disks on the plate

  5. Incubate at 25° for a few days

  6. Calculate the zone of inhibition around the disks
• Culturing microorganisms-Notes

  -Agar plate can be easily contaminated so be carful to sterilise everything

  -Sterilise agar plate, inoculating loop, work surfaces etc

  -Once the petri dish is sealed don't open it
• Ways to prevent contamination

  -Sterilise equipment

  -Seal petri dishes

  -Disinfect work surfaces
• Aseptic technique


  Precautions to prevent any contaminations by ensuring there are no contaminants like pathogens or dust in an area
• Effects of osmosis on plant tissue-method

  1. Peel a potato or other suitable vegetable

  2. Use a cork borer to produce multiple cylinders of potato

  3. Trim the potato to the same length

  4. Measure the mass and length of each cylinder

  5. Place each cylinder in a test tube and add 10cm³ of sugar solution, varying the concentration of sugar with each test tube

  6. Leave the potatoes over night

  7. Remove each cylinder and gently roll onto paper to reduce surface water

  8. Measure the length and mass of each cylinder
• Effects of osmosis on plant tissue-variables

  Independant-Concentration of sugar solution

  Dependant- Change in mass

  Control- Time, size of potato cylinder
• Effects of osmosis on plant tissue-notes

  -Make sure each cylinder is the same size

  -Gently dry the cylinders to remove surface moisture but not draw waster out of the cells
• Food tests-method


  1. Grind sample with a pestle and mortar with distilled water

  2. Transfer to a beaker and dissolve in more water

  3. Filter to remove suspended particles
• Food tests:starch-method

  Combine the sample with a few drops of iodine solution in a test tube
• Positive test for starch

  Solution turns blue-black

  
• Negative test for starch

  Solution remains orange

  
• Food tests:sugar-method


  1. Combine the sample and a few drops of Benedict's solution in a test tube

  2. Transfer the test tube to a beaker and half fill the beaker with hot water

  3. Leave for 5 minutes
• Positive test for sugar

  Green-Low concentration

  Yellow-Higher concentration

  Red-High concentration
• Food tests:protein-method


  1. Combine an equal amount of sample and biuret solution in a test tube
• Food tests:lipids-method


  1. Do not filter the solution

  2. Combine the sample with Sudan III in a test tube

  3. Shake gently
• Positive test for lipids


  Red layer floats to the top
• Negative test for lipids


  Solution remains the same
• Food tests:-notes


  -All the solutions are highly toxic

  -Sudan III contains ethanol which is highly flammable
• Effects of pH on amalyase-method

  1. Place a drop of iodine into each well of a spotting tile

  2. Place sugar solution, amylase solution and a buffer solution into separate test tubes and heat in a water bath for 10 minutes at 30°c

  3. Combine the 3 solutions into one test tube and stir with a glass rod

  4. Place the test tube back in the water bath and start a stopwatch

  5. Every 30 seconds place 1 drop of the solution into a well on the stopping tile

  6. If starch is present the solution will turn blue-black

  7. Record the time when the iodine stops changing colour

  
  

  8. Repeat with different pH levels
• Effects of pH on amalyase-notes

  -We only have an approximate time for when the reaction ends because of the period of time we take samples

  -The colour change will often be gradual

  - After mixing, the tube must be kept in the water bath.

  -Don't spill iodine on the skin
• Effects of pH on amalyase-variables

  Independent-pH

  Dependent-time taken for starch to be digested

  Control-temperature, concentration, volume
• Photosynthesis-method


  1. Place a boiling tube a certain distance away from an LED

  2. Fill the boiling tube with sodium hydrogen carbonate

  3. Place a piece of pond weed in the boiling tube

  4. Leave for 5 minutes so the pond weed can acclimatise

  5. Start a stopwatch and count the number of bubbles produced in a minute

  6. Repeat few more times and calculate a mean

  
  

  7. Repeat the whole experiment at different distances from the light source
• Inverse square law


  The intensity of radiation is inversely proportional to the square of the distance from the source of radiation

  
  

  Light α 1/distance²
• Photosynthesis-notes


  -An LED is used as they don't release much heat, if you're using a fluorescent lamp then place a beaker of water between the lamp and boiling tube

  -Make sure the cut end of the pond weed is facing upwards in the boiling tube

  -Bubbles are not always the same size

  -Alternatively use a funnel and measuring cylinder to capture the oxygen