Apparatus and Technique

Question 1

Colorimeter

Answer 1

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

Question 2

Apparatus + method

Answer 2

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

Question 3

Calibration curve definition

Answer 3

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

Question 4

Calibration curve

Answer 4

• 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

Question 5

Variables to control

Answer 5

• light intensity - wavelength of light - temperature - air movement - humidity

Question 6

Explain results

Answer 6

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

Question 7

Sources of error

Answer 7

• 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

Question 8

Calculating rate of transpiration

Answer 8

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

Question 9

Serial dilution

Answer 9

progressively diluting a concentrated solution by known dilution

Question 10

Ten fold serial dilution

Answer 10

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

Question 11

How to use a light microscope

Answer 11

• 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

Question 12

What is the eyepiece graticule

Answer 12

see through ruler fitted inside the eyepiece

Question 13

What is the stage micrometer

Answer 13

Slide with markings on it

Question 14

How to work out actual size using a light microscope

Answer 14

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

Question 15

micrometer to mm

Answer 15

1 micro = 0.001 mm

Question 16

Slide prep

Answer 16

• 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

Question 17

Staining

Answer 17

• 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

Question 18

Nuclei stain

Answer 18

nile blue

Question 19

Cytoplasm stain

Answer 19

easin

Question 20

Cell membrane

Answer 20

sudan blue

Question 21

General principle

Answer 21

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

Question 22

Common mistakes

Answer 22

• Sketchy lines- Curved labels

Question 23

Labelling

Answer 23

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

Question 24

Chromatography

Answer 24

Process used to separate mixtures of coloured complexes

Question 25

Paper chromatography

Answer 25

Uses paper as the stationary phase

Question 26

TLC

Answer 26

Uses a thin layer of absorbant methanol

Question 27

How does chromatography work

Answer 27

- 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

Question 28

Chromatography method

Answer 28

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)

Question 29

How to calculate RF

Answer 29

Distance travelled by compound / Distance travelled by solvent

Question 30

Electrophoresis

Answer 30

Using electricity to separate DNA fragments by length

Question 31

Process

Answer 31

- 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

Question 32

For

Answer 32

- very simple organisms - basic nervous systems

Question 33

Against

Answer 33

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

Question 34

Aseptic technique

Answer 34

Lab procedures that are performed under sterile conditions to prevent contamination

Question 35

Importance of aseptic technique

Answer 35

- avoids contamination- no nutrient contamination - unchanged conditions - no yield decrease - prevent micro organism escape

Question 36

Example of technique

Answer 36

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

Question 37

Dissection safety

Answer 37

- 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

Question 38

What is needed for fast diffusion

Answer 38

- High surface area - Short diffusion distance - High concentration gradient

Question 39

Adaptions for high surface area

Answer 39

- Branching e.g. trachea- Folding e.g. alveoli

Question 40

Adaptions for short diffusion distance

Answer 40

- Thin membranes

Question 41

Adaptions to maintain high concentration gradient

Answer 41

- Blood circulation - Ventilation of air

Question 42

How to prevent water loss

Answer 42

- Waxy cuticle - Close trachea/stomata- Trap moist air around holes

Question 43

How does trapping air around holes prevent water loss?

Answer 43

- Reduce water potential gradient - Reduce water vapour loss