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Biology > core practicals paper 2 > Flashcards

core practicals paper 2 Flashcards

1
Q 
topic 1 
core prac 1
effect of caffeine concentration on Daphnia heart rate 
variables 
(5 control)
A

independent: caffeine concentration
dependent: heart rate of daphnia
control variables:
- temperature
- volume of solution
-stress of daphnia
- size of daphnia
- time of acclimatisation

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2
Q

topic 1
core prac 1
effect of caffeine concentration on Daphnia heart rate
method and outcomes

A

method
- remove 1 dapnia and place in cavity slide replace pond water with distilled, leave for 5 mins to acclimatise
- count heart rate under microscope for 30s then multiply by 2 to get beats per min. repeat with 2 more daphnia
- repeat again a 5 different caffeine concentrations
outcome
- as caffeine increases, heart rate increases

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3
Q

topic 1
core prac 1
effect of caffeine concentration on daphnia heart rate
possible evaluation issues

A
  • ensuring daphnia are the same size
  • left too long under microscope, temp increases due to lamp effecting heart rate
  • ensuring enough data is collected
  • too high conc. of caffeine kills daphnia
  • counting heart beat inaccurate
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4
Q 
topic 2
core prac 3 
the effect of temperature on cell membranes 
variables 
(3 control)
A

independent: temperature of water
dependent:% transmission of light through resulting solution
control
- volume of distilled water
- time left in water
- size of beetroot piece

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5
Q

topic 2
core prac 3
the effect of temperature on cell membranes
method, calculation and outcomes

A

method
- using a cork borer and knife cut pieces of beetroot into 1 cm length cylinders
- place in distilled water overnight to remove dye released on preparation. wash and blot dry
- place 8 boling tubes of distilled water into 8 water baths of different temperature. once at temperature add a piece of beetroot to each and leave for 30 mins.
- remove beetroot and shake tubes to disperse dye.
- set colourimeter to read % absorbance on blue/green filter calibrate using distilled water in a cuvette first
as temperature increased % transmission slightly increased to a point a which it greatly increased due to membrane molecules gaining more heat energy, vibrating more to a point where the vibrations caused large gaps in the membrane enabling the release of dye also protein in membrane denatured leaving large pores.

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6
Q 
topic 2 
practical 4 
the effect of changing enzymes concentration on rate of reaction 
variables 
(5 control)
A

independent: concentration of enzyme
dependent: time taken for enzyme to break down substrate
control:
- temperature
- volume of enzyme
- volume of substrate
- concentration of substrate
- pH

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7
Q

T-2 prac 4
the effect of changing enzyme concentration on rate of reaction.
protease version. method, calculations, conclusions

A

method
- make up different conc. of enzymes using distilled water. set up water bath for temperature to keep constant
- place 1 test tube of 5cm3 casein solution into water bath alongside second test tube containing 2cm3 of 0.2% trypsin.
- allow to acclimatise for 3 min so that at same temperature then add trypsion to casesin.
- time how long it takes ofr casein solution to turn transparent. repeat a further 2 times then repeat for concentration
calculation: rate = 1 / time
as conc of enzyme increase rate of reaction increases until a plateau point where all enzyme has metabolised all substrate

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8
Q

T-2 prac4
the effect of changing enzyme concentration on rate of reaction
using catalase in yeast and hydrogen peroxide
method, calculations, outcomes

A

method
- using 1st conc. of yeast solution, acclimatise to temp along with hydrogen perioxide. set up gas syringe
- add perioxide to yeat and attach syringe. read of volume of oxygen produced every 10 mins until3 reading are the same. repeat 3 times for each concentration of yeast solution.
rate = initial rate of reaction = gradient at steepest point of volume against time for each concentration

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9
Q

T2 prac 4
the effect of changing enzyme concentration on rate of reaction
evaluation points

A

protease
- maintaining constant temperature
- accurately making up the different concentrations
- identifying end point consistently
- difficult to see the cross through the solution
catalase and hydrogen perioxide
- attaching syringe can be slower allowing loss of gas
- inaccurate reading of syringe
- inaccurate reading of syringes in making up dilutions
- reaction going too quickly to read

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10
Q

T3 prac 5
observing mitosis
methods, calculations, outcomes

A

chromosomes stained blue using orcein ethanoic stain
- place test tube of 2cm3 of 1M HCl into 60oc water bath
- cut of 1-2 cm of root tip. place in watch glass containing 2cm3 of acetic alcohol for 12 mins.
- remove then place into another watch glass containing 5 cm3 of ice cold distilled water. leave 4-5 min remove and dry
-place tips into heated HCl for 5 mins then repeat process.
transfer 1 tip to microscope slide gently macerate with mounted needle add 1 small drop of orcein ethanoic stain and leave for 2 mins. add cover slip and blot with filter paper.
- view under microscope to observe mitosis.
calculations: percentage of cells in each stage of mitosis
mitotic index. the number of cell containing visible chromosomes + total number of cells in the field of view.

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11
Q

T3 prac 5
observing mitosis
evaluation issues (3)

A
  • resolution of microscope
  • human error in counting number of cells
  • enough time in the solution to enable successful maceration or staining
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12
Q

T4 prac 6
the strength of plant fibres
variables
(2 control)

A

independent. source and type of fibre
dependent. mass that can be held
control
length of fibre
- size of each individual mass

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13
Q

T4 prac 6
the strength of plant fibres
methods and outcomes

A

method

  • plant material should be left to soak in a bucket of water for a week so fibres can be easily extracted (retting)
  • once fibres are removed, connect between 2 clamp stands and gradually add mass in the middle until the fibre snaps try with individual fibres from different plants and different ways of combining
    outcomes: the more fibres combined together the stronger it is.
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14
Q

T4 prac 6
the strength of plant fibres
evaluation issues

A
  • maintaining length of fibres
  • ensuring consistency when twisting or plaiting
  • using fibres of the same age (as they get older they become more brittle)
  • extracting whole fibres that are useful.
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15
Q

T4 prac 7
investigating plant mineral deficiencies
variables
(4 controls)

A

independent. minerals present
dependent. physical characteristics of the plant
control
- volume of mineral solution
- species of plant
- size of container
- amount of light received

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16
Q

T4 prac 7
investigating plant mineral deficiencies
method

A
  • half fill a tube with all nutrients present solution. cover the tip with foil and push down on covering to create well.
    gently push the geranium roots of Mexican plant plant-let through hole so it is in solution. repeat with solutions lacking in nitrogen, phosphate, potassium, magnesium, calcium or lacking all. wrap all tube sin aluminium fill and place in tube holder on sunny window sill. observe regularly
17
Q

T4 prac 7
investigating plant mineral deficiences
observations

A
  • lacking nitrate. stunted growth with yellowed leaves. NO3- needed to make amino acids, nucleotides, chlorophyll, ATP and some plant growth substances
  • lacking calcium. gives gnarled and misshapen leaves. used in the formation of calcium pectate in the middle lamella, the glue between plant cells
  • lacking magnesium. causes leaves to yellow away from veins but stay green near them. important part of the chlorophyll molecule
18
Q

T4 prac 8
effect of garlic and mint on bacterial growth
variables
(4 control)

A

independent. presence of garlic or mint
dependent. zone of inhibition around disc
control:
- concentration of plant material
- lawn of bacteria on petri dish
- contamination of petri dish by other microbes
- same volume of plant material on each disk.

19
Q

T4 prac 8
effect of garlic and mint on bacterial growth
method and outcome

A

method

  • make plant extract by crushing 3g of plant material with 10cm3 of denatured alcohol. shake occasionally for 10 mins.
  • pipette 0.1 cm3 of extract onto sterile paper disc. allow to dry. meanwhile label agar plates and split into 4 sections.
  • place 1 disc of each extract in each quadrant, close and tape. leave to incubate overnight and observe zone of inhibition. carry out controls with just distilled water on discs
    outcomes: the control discs completely covered with bacteria, some plant extracts will create larger zones of inhibition than others, meaning they are more effective at lower concentrations
20
Q

T4 prac 8
effect of garlic and mint on bacterial growth
evaluation issues

A
  • growth of unwanted microbes on agar plate due to bad aseptic technique
  • not shaking extract enough to ensure enough active ingredient
  • inconsistency when adding plant extract to paper discs
  • contaminating controls
  • using wrong species of bacteria for lawn
21
Q

T4 prac 9
viewing plant fibres
method

A

cut section of a stem, transfer to a watch glass of water, transfer to slide, draw around with crayon add the dye (acidified phloroglucinol) and a cover slip, view under microscope, draw a low power plan

22
Q

T7 prac 16
measuring the rate of oxygen uptake / rate of respiration
method

A
  1. place 5g of organism into tube and replace bung. soda lime in the bottom to remove CO2 produced.
  2. put drop of glass in glass tube. open the connection to the syringe and move the fluid to convenient place on the pipette. mark the starting position.
  3. isolate resporimoter. stark stop clock. mak the position of fluid at 1 min intervals for 5 mins.
  4. at end open the connection to outside. measure distance travedlled by liquid each minute. convert distance into volume of oxygen ( Pi r^2 X distance moved)
  5. record results and calculate mean rate of oxygen uptake.
23
Q

T7 prac 16
measuring the rate of oxygen uptake / rate of respiration
outcomes

A

oxygen molecules are absorbed by the organism and used in respiration. the same number of CO2 molecules are released bu these are absorbed by the soda lime. this reduces the pressure inside the test tube (fewer molecules lower pressure). atmospheric pressure pushes the liquid along the tube, until the pressure in and outside the tube is equal. oxygen is the final acceptor and it eventually combines with hydrogen to make water. CO2 comes from CO2 released in the link reaction and the krebs cycle as the carbohydrate is broken down

24
Q

T7 prac 17 spirometry

metiod

A

the spirometer is effectively a tank of water with an air filled chamber suspended in the water. it is set up so that adding air to the chamber makes the lid rise. movements are recorded using a kymograph. tubes run from the chamber to a mouthpiece and back again. the volume of air the person inhales and exhales can be calculated from the distance the lid moves. apparatus can be calibrated so that the movement of the lid corresponds to a volume. canister of soda lime absorbs the CO2. after calibration the spirometer is filled with oxygen. nose clip. after normal breathing the subject will take as deep a breath as possible to give vital capacity

25
Q

T7 prac 17 spirometry

outcomes

A

the tidal volume is the volume of air breathed in and out at rest. tidal volume is 0.5 dm3. vital capacity is the maximum.
breathing rate is the number of breaths taken per minute
minute ventilation is the volume of air breathed into and out of the lungs in one minute
= tidal volume X rate of breathing
some air always remains in the lungs as residual air and cannot be breathed out. residual air prevents the walls of the bronchi oles and aveoli sticking together.

26
Q

T7 prac 16 evaluation of a simple respirometer

A
  • does not allow you to reset
  • it needs a control tube used alongside it
  • no scale so measurements likely to be less accurate
    adv
  • very simple to set up
  • minimal number of connections makes a good seal easier to obtain
27
Q

T7 prac 16 evaluation of a U tube respirometer

A
  • tendency for the connections to leak
  • expensive
    adv
    0 does not need to have an additional control as the second tube balances out the effects of changes in temperature or atmospheric pressure
  • syringe allows you to move the liquid in the U to reset the apparatus
28
Q

T8 prac 18 investigating habituation to a stimulus

variables

A

independent: number of pokes
dependent: retraction time
control:
- replication using snails of approx same size and age
- equal handling history
- drying out

29
Q

T8 prac 18 investigating habituation to a stimulus

method

A
  • collect one giant african land snail and place it on a clean, firm surface.
  • allow the snail to get used to its new surroundings for a few minutes until it has fully emerged from its shell. dampen a cotton wool bud with water.
    firmly touch the snail beteeen the eye stalks with dampened cotton bud and immediately start the stopwatch.
    measure the length of time between the touch and the snail being fully emerged from its shell once again, with its eye stalks fully extended. repeat the procedure in step 3 for a total of 10 touches, timing how long the snail takes to reemerge each time. record your results in a suitable table. present in graph
30
Q

T8 prac 18 investigating habituation to a stimulus

outcome

A

spearman’s rank stats test to look for correlation in data.
there is a negative correlation, as the number of stimuli increase the time taken for the snail to re-emerge decreases. student should make a reference to the data.
with repeated stimulation Ca2+ channels in the presynaptic membrane become less responsive. less Ca2+ crosses the membrane into the presynaptic neurone. as a result less neurotransmitter is released into the synaptic cleft. this means that an action potential across the postsynaptic membrane is less likely. fewer action potentials are produced in the postsynaptic motor neurone so less of a response is observe.

31
Q

T8 prac 18 investigating habituation to a stimulus

evaluation

A
  • snails already handled before the experiment may not react in the same way
  • determining when a snail has fully emerged
  • lack of moisture may encourage snail to stay more in its shell
  • measuring eye stalk length instead.

Biology (13 decks)

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