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AQA A Level Biology > Apparatus and Techniques > Flashcards

Apparatus and Techniques Flashcards

1
Q

Colorimeter

A

An instrument used to quantitatively measure the intensity of a colour of a solution

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2
Q

Apparatus + method

A
  • curettes are special rectangular test tubes - use a blank filled with distilled water to 0 each reading - make a calibration curve
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3
Q

Calibration curve definition

A

a method for determining the conc of an unknown solution by comparing it to a range of known concentrations

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4
Q

Calibration curve

A
  • use serial dilutions of known concs of reducing sugar - heat with excess known conc of benedicts solution- use same volumes of solutions each time- zero colorimeter using a blank- read results using transmission/absorbance - plot on a graph = calibration curve- test unknown sugar in same way- colour change, blue -> green -> yellow -> red
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5
Q

Variables to control

A
  • light intensity - wavelength of light - temperature - air movement - humidity
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6
Q

Explain results

A

as leaves are covered/ removed- surface area of leaves decreases - number of stomata decreases - transpiration decreases - cohesion-tension decreaseswhen all leaves covered or removed- some evap (not transpiration)- from upper surface of leaves

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7
Q

Sources of error

A
  • water used to make cells turgid - water used by photosynthesis - water made by respiration - leaks in apparatus - not all stomata removed- stem not cut under water (allowing air into xylem which breaks cohesion-tension)- error in reading miniscus
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8
Q

Calculating rate of transpiration

A

(( distance bubble moved ) x ( cross sectional area of capillary tube )) / time taken

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9
Q

Serial dilution

A

progressively diluting a concentrated solution by known dilution

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10
Q

Ten fold serial dilution

A
  • 1cm3 of initial- added to 9cm3 of distilled - mix until homogenous - 1cm3 transferred to next
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11
Q

How to use a light microscope

A
  • Start with lowest power mag objective lens - put the slide onto a stage and hold in place using stage clips- use the course focus to move the stage as close to the lens as possible without touching - look through eye piece and move focus so stage moves away from the lens and comes into focus - adjust fine focus and light intensity for clearest image - repeat with higher power lens if necessary
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12
Q

What is the eyepiece graticule

A

see through ruler fitted inside the eyepiece

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13
Q

What is the stage micrometer

A

Slide with markings on it

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14
Q

How to work out actual size using a light microscope

A

1 - set mag2 - record how many eyepiece graticule units is equal to 1 micrometer 3 - don’t change mag4 - view specimen5 - use scale to work out actual size

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15
Q

micrometer to mm

A

1 micro = 0.001 mm

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16
Q

Slide prep

A
  • Add a few drops of water to blank microscope slide - Use forceps to pick up sample- Thin enough sample so light shines through - Place onto microscope slide - Use pipette to add stain - Place cover slip on top - Put slide on microscope stage - Adjust mag
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17
Q

Staining

A
  • Identify cellular components - Identify different cell types in a tissue - only see parts that absorb light - stains make more parts of the cell absorb light (become visible)- different stains for different cells
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18
Q

Nuclei stain

A

nile blue

19
Q

Cytoplasm stain

A

easin

20
Q

Cell membrane

A

sudan blue

21
Q

General principle

A
  • Sharp HB pencil- Clear continuous lines- No sketching- No shading- Draw only what you see- Square guidelines - Whole page - Rubber- Include titre - Include scale
22
Q

Common mistakes

A
  • Sketchy lines- Curved labels
23
Q

Labelling

A
  • Sharp pencil- Use a ruler - No arrow heads - No crossing lines- Annotate structures - Underline species name
24
Q

Chromatography

A

Process used to separate mixtures of coloured complexes

25
Q

Paper chromatography

A

Uses paper as the stationary phase

26
Q

TLC

A

Uses a thin layer of absorbant methanol

27
Q

How does chromatography work

A
  • mixture contains more than one compound, each compound has a different solubility - the mobile phase moves through the stationary phase- the more soluble, the further it moves - compounds separate in order of solubility
28
Q

Chromatography method

A

1 - Add conc spot of mixture to the bottom of stationary phase2 - End of chromatography strip is lowered into solvent 3 - Pigments/ compounds are carried different distances according to solubility4 - if compounds not visible use a stain5 - Stop before solvent reaches the end of the stationary phase6 - Identify compounds by comparing results to known sample (RF)

29
Q

How to calculate RF

A

Distance travelled by compound / Distance travelled by solvent

30
Q

Electrophoresis

A

Using electricity to separate DNA fragments by length

31
Q

Process

A
  • DNA negatively charged - attach a fluorescent label or stain DNA - put DNA fragments into well at negative end - turn on current - DNA fragments attracted to positive electrode - Small fragments move further faster- 3 fragments = 2 cuts
32
Q

For

A
  • very simple organisms - basic nervous systems
33
Q

Against

A
  • cannot consent - could be fatal - do not know what they feel- use of animals is wrong
34
Q

Aseptic technique

A

Lab procedures that are performed under sterile conditions to prevent contamination

35
Q

Importance of aseptic technique

A
  • avoids contamination- no nutrient contamination - unchanged conditions - no yield decrease - prevent micro organism escape
36
Q

Example of technique

A

1 - Disinfect work area2 - Flame inoculating loop after transfer 3 - Flame mouth of glass bottle 4 - Don’t put bottle tops on bench 5 - Quickly replace lid

37
Q

Dissection safety

A
  • Use scissors instead of scalpel where possible - Replace blade covers when not in use - Make cuts with blades facing away from you - Wear safety goggles- Sterilise equipment
38
Q

What is needed for fast diffusion

A
  • High surface area - Short diffusion distance - High concentration gradient
39
Q

Adaptions for high surface area

A
  • Branching e.g. trachea- Folding e.g. alveoli
40
Q

Adaptions for short diffusion distance

A
  • Thin membranes
41
Q

Adaptions to maintain high concentration gradient

A
  • Blood circulation - Ventilation of air
42
Q

How to prevent water loss

A
  • Waxy cuticle - Close trachea/stomata- Trap moist air around holes
43
Q

How does trapping air around holes prevent water loss?

A
  • Reduce water potential gradient - Reduce water vapour loss

AQA A Level Biology (13 decks)

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