Required Practicals Paper 1 Flashcards

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1
Q

General tips (not a flashcard just read)

A
  • Mention all the equipment
  • State safety measures
  • Remember variables
  • State how you will get accurate data by reducing errors and uncertanties
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2
Q

Parts of the microscope and their role

A
  • Stage + clips - where the slide goes
  • Lamp - passes light through the slide
  • Objective lenses - lenses with magnifications of 4x 10x and 40x
  • Eyepiece - where you look through and has a lense with 10x mag
  • Coarse focus
  • Fine focus
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3
Q

How to prepare an onion cell slide

A
  • Wash the onion and peel a one cell layer of skin using a scalpel and tweezers
  • Clean slide and coverslip
  • Put thin onion strip onto the slide and reposition using a toothpick
  • Add a drop of iodine onto the onion - this stains the cells so they can be seen
  • Slantly put the coverslip on so no air bubbles form
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4
Q

How to use the microscope to view a prepared slide

A
  • Put it on the stage and attach the clips to hold it in place
  • Use the lowest power objective lens
  • Turn the coarse focus dial until the lens nearly touches the slide
  • Look through the eyepiece and slowly turn the coarse focus dial until the cells come into focus
  • Use the fine focus dial to bring the cells into a clear focus
  • Repeat using different objective lenses and turn the fine focus dial

REMEMBER, INCLUDE A MAGNIFICATION SCALE IN YOUR DRAWING

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5
Q

How to grow bacteria in the lab

A
  • Nutrient broth solution
  • Agar gel plate with nutrients
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6
Q

Aspetic technique to prepare an uncontaminated bacterial culture

A
  • Sterilise petri dishes, nutrient broth and agar
  • Sterilise the inoculating loop by passing it through a bunsen flame
  • Inoculate the agar with the bacteria but only open the lid slightly so less airbourne pathogens can get in
  • Do this near the bunsen flame to kill airbourne pathogens as they move towards the flame
  • Add 2 pieces of Cellotape to the lid to stop bacteria entering, leaving and to allow oxygen to enter
  • Label, store upside down (stop condensation falling) in an incubator at 25 degrees (prevent growth of harmful human pathogens)
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7
Q

How to investigate the effect of an antibiotic on a bacterial growth

A
  • Same method as before but add sterile filter paper disks with the antibiotic onto the plate
  • After a few days, you should observe that around the antibiotics, there are no bacteria growing
  • This is called the zone of inhibition
  • The effefct of the antibiotic can be calculate using the area of the zone of inhibition
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8
Q

How to investigate the effects of osmosis on plant tissue

A
  • Peel the potato to remove the skin
  • Use a cork borer to produce 5 potato cylinders with the same duameter and a scalpel to trim them to the same length
  • Record the mass using a mass balance
  • Add each potato cylinder to a test tube and add 10cm3 of distilled water, 0.2mol sugar solution with increases of 0.2 each time
  • After 24hrs, remove the potatoes and gently roll them on a paper towel to remove excess water than hadn’t been absorbed (surface moisture)
  • Record the new mass
  • Find the percentage change and plot a graph
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9
Q

How to prepare a sample of food for a food test

A
  • USing distilled water, grind the food using a pestle + mortar to get a paste
  • Transfer to a beaker, add water and stir so all the chemicals in the food dissolve in the water
  • Filter the solution to remove suspended food particles
  • This produces a food solution
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10
Q

How to test for lipids

A
  • Add a few drops of distilled water and ethanol
  • Shake gently
  • If lipids are present, a cloudy white emulsion forms
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11
Q

How to test for carbohydrates

A
  • Add iodine SOLUTION to the food solution
  • If carbs are present, the iodine solution will turn form orange to blue-black
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12
Q

How to investigate the effect of pH on amylase

A
  • Place one drop of iodine solution into each well of a spotting tile
  • Set up 3 test tubes - one with 2cm3 starch soltuion, one with 2cm3 amylase solution and the last with 5cm3 pH buffer solution (to control the pH)
  • Place all test tubes in a 30 degrees water bath. Leave for 10 mins to equilibrate
  • Combine all solutions, mix, return to water bath and start a timer
  • At 30 second intervals, transfer one drop of solution to a well until the iodine remains orange
  • Repeat the whole experiment using different pH buffers (6,7 and 8)
  • Plot a graph which will be a curve and the lowest point is the optimum pH
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13
Q

Problems with the pH amylase experiment

A
  • 30 second samples may not be frequent enough so the time is only approximate
  • The colour change tends to be gradual so it is hard to tell when the iodine isn’t blue-black
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14
Q

Method for photosynthesis practical

A
  • Place LED 10cm away from boiling tube
  • Fill boiling tube with water and sodium hydrogen carbonate (release carbon dioxide)
  • Add pondweed with cut end at the top and leave to acclimatise
  • After 5 mins, start a stopwatch and count the number of bubbles produced in one minute
  • Repeat to find a mean
  • Repeat at different distances e.g. 20cm, 30cm
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15
Q

Relationship between light intenisty and distance from light source

Inverse square law

A
  • As distance increases, light intensity decreases
  • Light intensity is proportional to the inverse of the distance from the light squared
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16
Q

Control variables for photsynthesis practical

A
  • Temperature
  • Type of light source
  • Concentration of bicarbonate
  • Piece/species of pondweed
17
Q

Problems with the photosynthesis and the solution

A
  • Bubbles may be too fast to count accurately
  • Bubbles aren’t the same size so a small bubble would be the same as a large bubble even though the large bubble has more oxygen
  • This is fixed by using an inverted measuring cylinder filled with water to measure the volume of oxygen produced in a set amount of time