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biology paper1 > required practices > Flashcards

required practices Flashcards

1
Q

describe the method to view a prepared slide

A
  1. place slide onto stage using clips to hold in place
  2. select lowest power objective lens (4x)
  3. position lense so it almost touches the stage
  4. look through eye piece
  5. turn coarse focussing dial until cells in clear focus
  6. use fine focussing dial
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2
Q

how do you calculate total magnification

A

eyepiece lense x objective lense

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3
Q

how to avoid contamination when culturing microorganism

A
  • stertlise all petri dishes, bacteria broth and agar
  • pass inoculating loop through flame
  • close lid to plate and use tape to seal shut
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4
Q

what is the optimum temperature for culturing microorganisms

A

25degrees celcius

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4
Q

what are the steps for carrying out culturing microorganisms

A
  1. clean bench with disinfectant
  2. sterilise innocculating loop
  3. open agar plate near bunsen burner
    4.use loop to spread chosen bacteria
  4. place sterile filter paper discs containing antibiotics onto the plate
  5. inculcate at 25 degrees
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5
Q

what is the region that no bacteria grows called

A

zone of inhibition

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6
Q

what does a bigger area of inhibition tell you

A

the antibiotic was more effective

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7
Q

what is the definition of osmosis

A

diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

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8
Q

what happenes to a plant cell when placed in water

A

expands - water moves in

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9
Q

what happenes to a plant cell when placed in concentrated solution

A

shrinks - water moves out

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10
Q

what are the steps for effect of osmosis practical

A
  1. peel potato
  2. use cork borer to produce 3 cyclinders of equal width
  3. use scalpel to trim cylinders to 3cm
  4. measure length using ruler and mass using balance
  5. place each cylinder into a test tube
  6. add 10cm3 0.5 molar of sugar solution to 1st test tube
  7. add 10cm3 0.25 molar of sugar solution to 2nd test tube
  8. add 10cm of distilled water to 3rd test tube
  9. leave potato overnight
  10. remove and pat dry
  11. measure length and mass and calculate % change
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11
Q

what were the results for the osmosis experiment

A

in water = gain mass
in sugar solution = loose mass

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12
Q

how do you make food solution

A
  1. take food sample and grind with distilled water using mortar and pestle
  2. transfer to beaker and add more distilled water so chemicals in food dissolve in water
  3. filter
  4. test for chemicals present
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13
Q

how to test for carbohydrates

A
  1. place 2cm3 of food solution into a test tube
  2. add few drops of iodine
  3. if turns blue-black starch is present
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14
Q

how to test for sugars

A
  1. place 2cm3 of food solution into a test tube
  2. add 10 drops of Benedict’s solution which is blue
  3. place in hot water
  4. leave for 5 min
  5. if sugar present solution will change colour (green, yellow, brick-red)
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15
Q

how to test for protein

A
  1. place 2cm3 of food solution into a test tube
  2. add 2cm3 of biuret solution - blue colour
  3. if present will turn purple or lilac
16
Q

how to test for lipids

A
  1. grind but do not filter
  2. place 2cm3 of food solution into a test tube
    .3. add few drops of distilled water and ethanol
  3. gently shake solution
  4. if present white cloudy emulsion will form
17
Q

method for testing effect of pH on amylase

A
  1. place one drop of iodine solution into each spotting tile
  2. first test tube has 2cm3 of starch solution
  3. second has 2cm3 of amylase solution
  4. third has 2cm4 of pH 5 buffer solution
  5. place all in water bath at 30˚ for 10 min
  6. combine all 3 solutions and mix
  7. return to water bath and start stopwatch
  8. after 30 sec use stirring rod to transfer 1 drop of solution to spotting tile
  9. turn blue-black if starch present
  10. take sample every 30 sec until iodine stays orange
  11. repeat several times using different pH buffers
18
Q

what problems are there with effect of pH on amylase practical

A
  • only taking samples every 30 sec -> only have approximate time for reaction to complete
  • not always obvious when iodine is no longer blue-black –> colour change gradual
19
Q

whats the method for the photosynthesis practical

A
  1. put 10cm piece of pondweed into a beaker of water
  2. cover with inverted filter funnel
  3. put pondweed 1m away from light source
  4. start stopwatch + count number of bubbles in 3 minutes
  5. record value of gas produced
  6. then move light source 80cm away
  7. refill cylinder with water and repeat steps 4 and 5
  8. repeat with distances of 60cm, 40cm and 20cm

biology paper1 (10 decks)

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