Required practicals
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RP2- Calculating mitotic index of root cells. Why is the onion/ garlic bulb suspended in water?
To stimulate cell division
RP2- Calculating mitotic index of root cells. Why is root tip placed in ethanoic alcohol?
To stabilise the chromosomes
RP2- Calculating mitotic index of root cells. Why is root tip placed in HCL and heated for 5 mins at 60 degrees
Helps separate cells by breaking down intracellular molecules
RP2- Calculating mitotic index of root cells. Why are roots rinsed in water for 5 mins
To remove any HCL- ensuring chromosomes are not damaged
RP2- Calculating mitotic index of root cells. Why are root tips pushed hard down on and why can no sliding occur
To ensure light can penetrate the cells- thin layer Sliding will damage chromosomes
RP1- Investigation into the effect of a named variable on the rate of enzyme-controlled reaction How will temperature be maintained
Use a thermostatically controlled water bath
RP1- Investigation into the effect of a named variable on the rate of enzyme-controlled reaction How will amount of enzyme be controlled?
Use enzyme solutions of known concerntrations Keep enzymes in same favourable conditions when storing
RP3- Production of a dilution series of a solute to produce a calibration curve to identify the water potential of plant tissue Why can’t chips be too large?
Wont fit into tubes
RP3- Production of a dilution series of a solute to produce a calibration curve to identify the water potential of plant tissue Why cant chips be too small?
Small inaccuracies are a higher proportion when dimensions are small
Calculating degrees of freedom Chi squared
Number of classes-1
Degrees of freedom Student T test
(n1-1) + (n2-1)
RP4- Investigation into named variable on cell membrane permeability Why is beetroot washed before being added?
Removes pigment from damaged cells Only pigment that leaves cells via membranes will be measured
RP4- Investigation into named variable on cell membrane permeability Suggest why cylinders are 65 mm long
Enough cells to detect change in pigment Not too big that beetroot wouldnt fit
RP4- Investigation into named variable on cell membrane permeability Suggest why 25 cm^3 of water is added to each test tube
Enough to cover all beetroot cells Not too much that the pigment is very diluted
RP4- Investigation into named variable on cell membrane permeability Suggest why 25 cm^3 of water is added to each test tube
Enough to cover all beetroot cells Not too much that the pigment is very diluted
RP5: Dissection of animal or plant gas exchange or mass transport system or of organ within such a system How to reduce injury / infection
Cut away from body When holding sharp items- hold downwards Ensure to sterilise equipment after use
RP6- Effect of antimicrobial substances on microbial growth Name some aseptic techniques
Wearing goggles and labcoats Use bleach to clear area Keep petri dish closed as much as possible Use flame to sterlise equipment before use Wash hands
RP6- Effect of antimicrobial substances on microbial growth Why is mouth of beaker put in flame
The heat creates a convection current which drives air away from the bottle Prevents air bourne microorganisms from entering
RP6- Effect of antimicrobial substances on microbial growth Why is blue flame used rather than a yellow flame?
Blue flame is hotter-hot enough to kill microorganisms and cause air to move ou of bottle
RP6- Effect of antimicrobial substances on microbial growth How does incubating dishes at room temperature reduce danger
Prevents growth of organisms which thrive at body temperature Reduces chance of pathogenic bacteria forming
RP6- Effect of antimicrobial substances on microbial growth What would make a suitable control experiment
Repeat paper disks soaked in water Proves that it is antibiotic which kills the bacteria
RP6- Effect of antimicrobial substances on microbial growth What needs to be controlled so that the results can be compared
Concentration of nutrients in agar Temperature and pH SPecies of bacteria Time plates are left for Concentration of antibiotics
RP8- The effect of wavelength of light on dehydrogenase activity in chloroplasts What is the purpose of container of water between the lamp and experimental tubes
Acts as a heat sink Prevents rate of reaction in tubes being affected by temperature Prevents Enzymes from being denature
RP9- Investigation into the effect of a named variable on rate of respiration What volume of water is ideal to use for water bath
1dm Loses heat slowest Needs water added less often