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Required practicals > Biology > Flashcards

Biology Flashcards

1
Q

RP 1:

What does resolution mean?

A

RP 1:

The ability of a microscope to distinguish detail, the minimum distance at which two distinct points of a specimen can be seen as separate objects

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2
Q

RP 1:

Which Microscope is used in this required practical?

A

RP 1:

Light microscope

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3
Q

RP 1:

How do light microscopes work?

A

RP 1:

They use light and lenses to form an image of a specimen and magnify it

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4
Q

RP 1:

What will you be observing in the Required practical?

A

RP 1:

Onion Cells

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5
Q

RP 1:

What’s the First step of Preparing a slide?

A

RP 1:

1.) Add a drop of water to the middle of a clean slide

(Allows sample to be suspended between slide and coverslip, and ensures coverslip stays in place)

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6
Q

RP 1:

What’s the Second Step of Preparing the Slide?

A

RP 1:

2.) Cut up an onion and separate it out into layers. Use tweezers to peel of some Epidermal tissue from the bottom of one of the layers

(A thin sample should be used to allow light to pass through and highlight internal structures)

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7
Q

RP 1:

What’s the Third Step of Preparing the Slide?

A

RP 1:

3.) Using the tweezers, place the Epidermal tissue into the water on the slide

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8
Q

RP 1:

What’s the Fourth Step of Preparing a Slide?

A

RP 1:

4.) Add a Drop of iodine solution onto the Epidermal tissue. The Iodine Solution is a Stain. Stain are used to Highlight Objects in a cell by Adding Colour to them

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9
Q

RP 1:

What’s the Fifth Step of Preparing a Slide?

A

RP 1:

5.) Place a Coverslip (a square of thin, transparent plastic or glass) on top of the epidermal tissue. To do this stand the Coverslip upright next to the water droplet and carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles as it may obstruct your view of the specimen.

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10
Q

RP 1:

Explain how you Prepare a Specimen on a Slide, ready to be viewed through a Light Microscope.

A

RP 1:

  1. ) Add a drop of water in the middle of a clean slide
  2. ) Cut up on onion and separate it into layers. Use tweezers to peel some epidermal tissue from the bottom of one of the layers
  3. ) Using tweezers, Place the epidermal tissue into the water in the slide
  4. ) Add a drop of iodine solution to the onion on the slide
  5. ) Place a Cover Slip over the specimen
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11
Q

RP 1:

Explain how you setup and use a light microscope to view a specimen on a slide.

A

RP 1:

  1. ) Clip the slide you’ve prepared onto the stage
  2. ) Select the lowest powered Objective lens
  3. ) use the coarse adjustment knob to move the stage up to just below the objective lens
  4. ) Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly focused
  5. ) Adjust the fine adjustment knob, until you get a clear image of whats on the slide
  6. ) If you need to see the slide with a greater magnification, swap to a higher-powered objective lens and refocus.
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12
Q

RP 1:

What’s the First Step of using the Microscope to Observe the Specimen?

A

RP 1:

1.) Clip the slide you’ve prepared onto the stage

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13
Q

RP 1:

What’s the Second Step of using the Microscope to Observe the Specimen?

A

RP 1:

2.) Select the lowest powered Objective lens

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14
Q

RP 1:

What’s the Third Step of using the Microscope to Observe the Specimen?

A

RP 1:

3.) use the coarse adjustment knob to move the stage up to just below the objective lens

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15
Q

RP 1:

What’s the Fourth Step of using the Microscope to Observe the Specimen?

A

RP 1:

4.) Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly focused

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16
Q

RP 1:

What’s the Fifth Step of using the Microscope to Observe the Specimen?

A

RP 1:

5.) Adjust the fine adjustment knob, until you get a clear image of what’s on the slide

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17
Q

RP 1:

What’s the Sixth Step of using the Microscope to Observe the Specimen?

A

RP 1:

6.) If you need to see the slide with a greater magnification, swap to a higher-powered objective lens and refocus.

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18
Q

RP 1:

what must you remember to include when drawing your observations of the specimen (Onion cells)

A

RP 1:

  • Draw in pencil
  • make sure the lines are clear and unbroken (Draw the cells + Subcellular structures in clear, unbroken lines)
  • Remember not to include any colouring or shading
  • Draw the Cells + Subcellular Structures in proportion (The correct sizes Relative to each other)
  • if you’re asked to make your drawing in a certain amount of space (e.g. on a worksheet), it need to take up at least half the space
  • Include a Title of what you’re observing
  • label the important feature of what you’ve drawn (e.g. Cell wall, nucleus, cytoplasm)
  • work out the magnification
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19
Q

RP 1:

How can you find the size of a sub-cellular structure by comparing it to the size of the cell it is located in?

A

RP 1:

  1. ) Estimate the number of times that the sub-cellular structure could fit across the width of the cell
  2. ) Divide the cell by the number of times the sub-cellular structure would fir across it.
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20
Q

RP 1:

What other way could you find the size of a subcellular structure instead if comparing the size of the cell it’s located in?

A

RP 1:

if the subcellular structure closely resembles a shape (e.g. a mitochondria resembles a rectangle), like a rectangle for example, you can time the width by the height

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21
Q

RP 1:

What equipment will this experiment need?

A

RP 1:

● Light microscope
● Microscope slide
● Cover slip
● Onion
● Forceps
● Iodine solution
● White tile
● Scalpel
● Any other prepared plant and animal cell slides
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22
Q

RP 1:

Safety precautions

A

RP 1:

Wear safety goggles when handling the iodine solution.

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23
Q

RP 1:

How do you convert millimetres into micrometres?

A

RP 1:

x1,000

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24
Q

RP 1:

How do you convert micrometres into nano metres?

A

RP 1:

x1,000

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25
Q

RP 1:

How do you convert nano-metres in micrometres?

A

RP 1:

/ (divide by) 1,000

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26
Q

RP 1:

How do you convert micrometres into nano-metres?

A

RP 1:

/ (divide by) 1,000

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27
Q

RP 1:

How do you convert millimetres into nano-metres?

A

RP 1:

x1,000,000

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28
Q

RP 1:

How do you convert nano-metres into millimetres?

A

RP 1:

/ (divide by) 1,000,000

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29
Q

RP 3:

What is the independent variable for this required practical?

A

RP 3:

Concentration of the solution that you bath the plant tissue in

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30
Q

RP 3:

What is the dependent variable of this required practical?

A

RP 3:

% change in mass of the potato chip

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31
Q

RP 3:

What is the control variable of this required practical?

A

RP 3:

  • Surface area of the chip
  • Time left in the solution
  • Variety of potato
32
Q

RP 3:

What range of sugar solutions is good to use?

A

RP 3:

0-40%

33
Q

RP 3:

Why is it important to dry off the potato chips?

A

RP 3:

To make sure you are not also measuring the mass of any water/moisture that may be attached to the potato chips

34
Q

RP 3:

What is the method for this required practical?

A

RP 3:

1) Use a balance to measure the mass of each potato chip
2) Place the potato chips inside 10cm^3 of solutions of varying concentrations in boiling tubes (One should be distilled water)
3) Leave them for a standard time of 30 minutes
4) Remove the potato chips
5) Dry them off thoroughly
6) Re-weigh them and write down the mass of each potato after 30 minutes
7) Calculate the change in mass by taking the starting mass off of the ending mass
8) Divide the change in mass by the starting mass of the potato and multiply it by 100 to get the percentage change in mass

35
Q

RP 3:

What is the First Step of this required practical?

A

RP 3:

1) Use a balance to measure the mass of each potato chip

36
Q

RP 3:

What is the Second Step of this required practical?

A

RP 3:

2) Place the potato chips inside 10cm^3 of solutions of varying concentrations in boiling tubes (One should be distilled water)

37
Q

RP 3:

What is the Third Step of this required practical?

A

RP 3:

3) Leave them for a standard time of 30 minutes

38
Q

RP 3:

What is the Fourth Step of this required practical?

A

RP 3:

4) Remove the potato chips

39
Q

RP 3:

What is the Fifth Step of this required practical?

A

RP 3:

5) Dry them off thoroughly

40
Q

RP 3:

What is the Sixth Step of this required practical?

A

RP 3:

6) Re-weigh them and write down the mass of each potato after 30 minutes

41
Q

RP 3:

What is the Seventh Step of this required practical?

A

RP 3:

7) Calculate the change in mass by taking the starting mass off of the ending mass

42
Q

RP 3:

What is the Eighth Step of this required practical?

A

RP 3:

8) Divide the change in mass by the starting mass of the potato and multiply it by 100 to get the percentage change in mass

43
Q

RP 3:

Why is it particularly important to measure the starting mass of the potato chip?

A

RP 3:

Even if the potato chips are cut to a very precise/standardised surface area there is no guarantee that they will have the same mass

44
Q

RP 3:

As the concentration of sugar solution increases what is the trend in results?

A

RP 3:

The percentage change in mass decreases as the concentration of sugar solution increases

45
Q

RP 3:

Aim:

A

RP 3:

To investigate the range of concentrations of salt or sugar solutions on the mass of plant tissue

46
Q

RP 3:

What equipment will this experiment need?

A

RP 3:

● Plant tissue eg. potato
● A cork borer
● A ruler
● A measuring cylinder
● Labels
● Boiling tubes
● A test tube rack
● Paper towels
● A sharp knife
● A while tile
● A range of salt or sugar solutions
● Distilled water
● A top-pan balance
47
Q

RP 3:

Safety precautions

A

RP 3:

Take care when handling cork borer and sharp knife

48
Q

RP 3:

Define osmosis

A

RP 3:

The movement of water from an area of higher water concentration (dilute solution), to an area of lower water concentration (concentrated solution), through a partially permeable membrane

49
Q

RP 3:

Why is a cork borer used to cut the potato cylinders?

A

RP 3:

Results in equally sized samples so changes in length and mass can be easily compared

50
Q

RP 3:

How do you calculate the % change in mass for each cylinder?

A

RP 3:

(FINAL MASS - INITIAL MASS)/ INITIAL MASS x 100

51
Q

RP 3:

How can we reduce the effect of errors in this practical?

A

RP 3:

By repeating the experiment and calculating a mean percentage change at each concentration

52
Q

RP 3:

A

RP 3:

53
Q

RP 4:

Outline how to prepare a food sample:

A

RP 4:

1) Break up a piece of food using a pestle and mortar
2) Transfer the food to a beaker and add distilled water
3) Stir the mixture with a glass rod to dissolve some of the food
4) Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food

54
Q

RP 4:

How do we test for the presence of starch in a sample?

A

RP 4:

Add iodine solution to the sample

55
Q

RP 4:

Outline how Iodine solution is used to test for starch:

A

RP 4:

1) Measure out 5cm³ of a prepared food sample in a test tube
2) Add a few drops of iodine solution and shake gently

56
Q

RP 4:

What is the outcome of a positive test for starch?

A

RP 4:

Solution changes from browny-orange to blue-black

57
Q

RP 4:

What is the outcome of a negative test for starch?

A

RP 4:

Solution remains browny-orage colour

58
Q

RP 4:

How do we test for the presence of a reducing sugar in a sample?

A

RP 4:

Add Benedict’s reagent to the sample

59
Q

RP 4:

Outline how Benedict’s reagent is used to test for reducing sugars:

A

RP 4:

1) Measure out 5cm³ of a prepared food sample in a test tube
2) Prepare a water bath - set to 75ºC
3) Add 10 drops of Benedict’s reagent to the test tube using a pipette
4) Place the test tube in the water bath for 5 minutes (Make sure the tube is pointing away from you)

60
Q

RP 4:

What is the outcome of a positive test for reducing sugars?

A

RP 4:

Solution will change from blue to:
•Green - Low concentration
•Yellow - Higher concentration
•Red - High concentration

61
Q

RP 4:

What is the outcome of a negative test for a reducing sugar?

A

RP 4:

Solution will remain blue

62
Q

RP 4:

How do we test for the presence of protein in a sample?

A

RP 4:

Add Biuret solution to the sample

63
Q

RP 4:

Outline how Biuret solution is used to test for proteins:

A

RP 4:

1) Measure out 2cm³ of a prepared food sample in a test tube
2) Add 2cm³ of Biuret Solution to the sample and mix the contents of the tube by gently shaking it

64
Q

RP 4:

What is the outcome of a positive test for proteins?

A

RP 4:

Solution will change from blue to pink or purple

65
Q

RP 4:

What is the outcome of a negative test for proteins?

A

RP 4:

Solution will remain blue

66
Q

RP 4:

How do we test for the presence of lipids in a soluion?

A

RP 4:

Add Sudan III Stain Solution to the sample

67
Q

RP 4:

Outline how Sudan III Solution can be used to test for lipids:

A

RP 4:

1) Measure out 5cm³ of a prepared food sample in a test tube
2) Add 3 drops of Sudan III Solution using a pipette into the test tube an gently shake

68
Q

RP 4:

What is the outcome of a positive test for lipids?

A

RP 4:

A bright red layer will form on top of the mixture

(Sudan III Solution stains lipids and separates mixture into two layers)

69
Q

RP 4:

What is the outcome of a negative test for lipids?

A

RP 4:

Solution will remain the same

70
Q

RP 4:

Safety precautions

A

RP 4:

  • Wear safety goggles - Iodine is an irritant, Biuret Solution contains chemicals
  • If chemicals contact skin, rinse instantly
  • Be careful handling the water bath
  • Sudan III Solution is highly flammable
71
Q

RP 4:

Potential sources of error:

A

RP 4:

Colour change of Benedict’s test and Biuret test may be subtle is the concentration of the tested molecule is low

72
Q

RP 4:

Iodine test for starch - Equipment:

A

RP 4:

● Food sample
● A test tube
● Iodine solution (0.01 mol/dm3)
● Pipettes

73
Q

RP 4:

Benedict’s test for reducing sugars - Equipment:

A

RP 4:

● Food sample
● A test tube
● Benedict’s solution
● Hot water bath
● Thermometer
● Pipettes
74
Q

RP 4:

Biuret test for proteins - Equipment:

A

RP 4:

● A test tube
● A 10cm^3 measuring cylinder
● Biuret solution

75
Q

RP 4:

Sudan III test for lipids - Equipment:

A

RP 4:

● Food sample
● Test tube
● Ethanol
● Distilled water

Required practicals (3 decks)

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