Experiments As/a

Front 1

Required practical 1: Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction

Interpreting graph

Back 1

• Compare initial rates of reaction
• Plateau (when?limiting factor?)
• Constant

Front 2

Required practical 1: Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction

Calculating initial rate of reaction

Back 2

Initial rate of reaction near to t=0

Position ruler as if trying to continue line below 0

Line along ruler

Gradient of tangent (Y/X)

Front 3

Required practical 2: Preparation of stained squashes of cells from plant root tips

Microscope-slide preparation

Back 3

Add drop of water to (glass) slide;

Obtain thin section (of plant tissue) and place onslide / float on drop of water;

Stain with/add iodine in potassium iodide;

Lower cover slip using mounted needle;

Front 4

Required practical 3: Production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue.

Serial dilution

Back 4

1. Test tube of solution

2. Same volume of water in other test tubes

3. Draw half of solution and mix into next

4. Half as concentrated as previous

Front 5

Required practical 3: Production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue.

Scale factor

Back 5

1. Known concentration of solution

2. Divide concentration by concentration you want to make

3. This will produce a scale factor

4. Divide volume of initial concentration by the scale factor

5. Top up with distilled water

Front 6

Required practical 3: Production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue.

Water potential of potato cells

Back 6

1. Identical size potato segments

2. Mass (mass balance)

3. Sucrose solutions (known concentrations)

4. Leave in solution for fixed amount of time

5. Remove chips and pat dry gently with a paper towel

6. Reweigh each group

7. Calculate percentage change in mass

8. Calibration curve showing % change in mass against sucrose solution

9. Point it crosses x-axis (water potential of sucrose same as that of the water potential)

Front 7

Required practical 4: Investigation into the effect of a named variable on the permeability of cell-surface membranes.

Factors affecting rate of diffusion

Back 7

Simple: Concentration gradient, thickness of exchange surface, surface area, temperature, pH

Facilitated diffusion: concentration gradient, number of channel/carrier proteins, temperature, pH

Front 8

Required practical 5: Dissection of animal or plant gas exchange system or mass transport system or of organ within such a system.

Ethical issues

Back 8

Unnecessary killing of animals

Front 9

Required practical 5: Dissection of animal or plant gas exchange system or mass transport system or of organ within such a system.

Dissecting a lung

Back 9

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Front 10

Required practical 6: Use of aseptic techniques to investigate the effect of antimicrobial substances on microbial growth.

Aseptic techniques

Back 10

Work near a bunsen flame, hot air, draws microbes up

Sterilise wire inoculation loop

Flame the neck of the glass container of broth just after its opened and before its closed (air away from container, unwanted organisms falling in)

Sterilise in an autoclave

Disinfect work surfaces

Front 11

Required practical 7: Use of chromatography to investigate the pigments isolated from leaves of different plants, eg, leaves from shade-tolerant and shade-intolerant plants or leaves of different colours.

Back 11

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