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A Level Biology AQA > CPACs & maths stuff > Flashcards

CPACs & maths stuff Flashcards

(62 cards)

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1
Q

CPAC 1: Rate of an enzyme controlled reaction

How is control set up in a practical measuring enzyme activity ?

A

Replace the enzyme solution with distilled water or boiled enzyme solution

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2
Q

CPAC 1: Rate of an enzyme controlled reaction

Outline the practical procedure used to measure the effect of temperature on enzyme activity using trypsin and milk

A
  • immerse equal volumes of trypsin and milk stored in different test tubes in a water bath for 5 minutes for the temperature to equilibrate
  • mix together and immediately start timing, record the time taken for the milk to be completely hydrolysed (become colourless/same as control set up)
  • test at least 5 temperatures with at least 3 repeats at each temp
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3
Q

CPAC 2: calculating mitotic index using plant cells

Where can plant cells undergoing mitosis be found ?

A

Meristem tissue as shoot and root tips

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4
Q

CPAC 2: calculating mitotic index using plant cells

Outline the procedure to prepare a root tip slide

A
  • warm 1M HCl to 60 degrees in a water bath
  • cut a root tip using a scalpel and add to HCl. Incubate for 5 mins
  • remove from HCl and wash with distilled water
  • cut the tip of the root top sample and place on slide
  • lower the cover slip down carefully ensuring no air bubbles
  • add a few drops of stain to make chromosomes visible
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5
Q

CPAC 3 : investigating water potential

What is the purpose of calibration curves ?

A

They are used to determine the concentration of an unknown sample by comparing it to a set of standard values with known concentrations

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6
Q

CPAC 3 : investigating water potential

How is a calibration curve used to find the concentration of plant tissue ?

A

Plot a calibration curve of percentage change in mass against concentration
Find the x-intercept where the plant tissue is isotonic to the sucrose solution

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7
Q

CPAC 3 : investigating water potential

Why are the potato discs left in solution for 20mins ?

A

To allow time for osmosis until the plant tissue reaches equilibrium with its surrounding solution

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8
Q

CPAC 3 : investigating water potential

Outline the procedure of investigating osmosis using potato tissue

A
  • make simple dilution of 1M sucrose to produce 5 concentrations. Add 5cm3 to 5 different testubes
  • cut a potato into equal sized chips and weigh
  • place a chip in each test tube and leave for 20 mins
  • take out dab the excess water and weigh them again
  • calculate the percentage change in mass
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9
Q

CPAC 3 : investigating water potential

Why is the percentage change used rather than the actual change in mass ?

A
  • potato chips may not all have the same starting mass
  • percentage change allows for comparison
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10
Q

CPAC 3 : investigating water potential

What are the controlled variables of this practical?

A
  • volume of sucrose solution
  • size of potato chips
  • length of time left in solution
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11
Q

CPAC 4: investigating cell membrane permeability

State 2 factors that affect the permeability of cell membranes

A
  • temperature
  • concentration of solvents
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12
Q

CPAC 4: investigating cell membrane permeability

How is beetroot used to measure the permeability of cell membranes ?

A
  • the higher the permeability the more red pigment that leaks out into the surrounding solution in a given time.
  • a calorimeter can be used to determine the absorbance, hence concentration of the pigment
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13
Q

CPAC 4: investigating cell membrane permeability

Outline the procedure to investigate the effect of temperature on the permeability of the cell membrane

A
  • cut beetroot into 6 identical cubes with scalpel
  • place each cube in a different test tube with equal volumes of distilled water
  • place each test tube into water baths ranging from 30-80 degrees
  • leave for 20 mins
  • filter each solution out into a cuvette and measure absorbance using calorimeter
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14
Q

CPAC 5: dissection

How should label lines in a diagram be drawn?

A

With a ruler, no arrows, without crossing other labels, in pencil

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15
Q

CPAC 5: dissection

How should a diagram be drawn ?

A

Large diagram - at least half the space given
No shading, single continuous lines (no sketching), in pencil

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16
Q

CPAC 6: aseptic techniques

State 6 aseptic techniques

A
  • wipe down surfaces with antibacterial cleaner before and after experiment
  • use a Bunsen burner in the work place so that convection currents draw microbes away from culture
  • flame the wire hoop before using it to transfer bacteria
  • flame the neck of any bottles before using them to prevent any bacteria entering the vessel
  • keep all vessels containing bacteria open for the minimum amount of time
  • close windows and door to limit air currents
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17
Q

CPAC 6: aseptic techniques

Why is bacteria incubated at 25 degrees C ?

A

To prevent the growth of pathogens which occurs at higher temperatures

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18
Q

CPAC 6: aseptic techniques

How can you compare the effectiveness of different antibiotics applied to the same bacteria ?

A
  • measure the diameter and calculate the area of the zone of inhibition on the agar
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19
Q

CPAC 6: aseptic techniques

What does the zone of inhibition indicate ?

A

Bacteria killed by antibiotic
The larger the zone, the more effective the antibiotic
If little or no zone of inhibition, the bacteria is likely resistant

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20
Q

CPAC 6: aseptic techniques

Why should the lid not be completely taped to the Petri dish?

A
  • to allow oxygen to enter the Petri dish, preventing the harmful growth of anaerobic bacteria
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21
Q

CPAC 7 : chromatography of photosynthetic pigments

State the factors affecting the rate of migration of different pigments

A
  • solubility
  • mass
  • affinity to the paper
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22
Q

CPAC 7 : chromatography of photosynthetic pigments

Outline the procedure of using chromatography to separate photosynthetic pigments

A
  • draw a horizontal pencil line 1cm above the bottom of the filter paper
  • add some acetone and use the pestle and mortar to grind up leaf sample to release pigments
  • use capillary tube to transfer the pigment onto pencil line
  • suspend the paper in the solvent so that the level of the liquid does not lie above the pencil line and leave until solvent has run up paper to near the top
  • remove the paper from the solvent and draw a pencil line marking where the solvent moved to
  • calculate the Rf
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23
Q

CPAC 8: dehydrogenase activity in chloroplasts

What is the function of dehydrogenase in chloroplasts ?

A

It catalysed the acceptance of electrons by NADP in the LD reactions

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24
Q

CPAC 8: dehydrogenase activity in chloroplasts

What is the purpose of DCPIP?

A

It’s a redox indicator dye and acts as an alternate electron acceptor instead of NADP
It turns from blue to colourless when reduced

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25
CPAC 8: dehydrogenase activity in chloroplasts Why is the plant extract chilled in an ice water bath?
To lower the activity of enzymes to provient them from breaking down chloroplasts
26
CPAC 8: dehydrogenase activity in chloroplasts How is the control set up ?
Fill a cuvette with chloroplast extract and distilled water
27
CPAC 8: dehydrogenase activity in chloroplasts How is light intensity controlled ?
Adjust the distance of the lamp from the set up Perform the practical in a dark room so that the only source of light is the lamp
28
CPAC 8: dehydrogenase activity in chloroplasts What is the function of the muslin cloth ?
To fileter out any debris in the ground leaf mixture but allowing chloroplasts to pass through
29
CPAC 8: dehydrogenase activity in chloroplasts Why are the stalks of the leaves removed before grinding ?
The stalks to don’t contain any chloroplasts
30
CPAC 8: dehydrogenase activity in chloroplasts Outline the procedure of investigating the effect of light intensity after chloroplast extract has been obtained
- set the colorimeter to the red filter. Zero using a cuvette containing chloroplast extract and distilled water (control) - place the test tube rack 30cm from light source and add DCPIP - immediately take a sample and add to cuvette. Measure the absorbance of this sample - take a sample and measure its absorbance every 2 mins for 10 mins - repeat for different distances from lamp up to 1metre
31
CPAC 9: respiration in single celled organisms What is the function of methylene blue in this practical ?
It’s a redox dye and acts as an alternate electron acceptor of electrons transferred during ATP synthesis It turns from blue - colourless indicating the end point
32
CPAC 9: respiration in single celled organisms Outline the procedure to investigate the effect of temperature on the rate of respiration of yeast
- set up a water bath at 35 degrees C - add equal volumes of yeast and glucose solution to 3 test tubes - place the test tubes in the water bath and leave them to equilibrate for 10mins - add 2cm3 of methylene blue to the test tubes and start the timer. Shake for 10 seconds and place the test tube back into water bath - record how long it takes for the methylene blue to change colour for each test tube - repeat at different temperatures
33
CPAC 10: Investigating simple animal responses How can a choice chamber be used to measure the favourable environment of a small organism ?
By setting up chambers in different quadrants with different environmental conditions Organisms will move to the quadrant they find favourable
34
CPAC 10: Investigating simple animal responses What factors must be controlled when repeating the experiment ?
Number of animals Environmental conditions Time allowed for animals to choose
35
CPAC 10: Investigating simple animal responses Which statistical test is used to analyse the results of this practical and why ?
Chi squared It compares the expected and observed values and tests if there is a significant difference
36
CPAC 10: Investigating simple animal responses What do animals do when they are in unfavourable environments ?
They move faster and change direction more frequently to increase chances of survival
37
CPAC 11: measuring the concentration of glucose using a calibration curve How can Benedict’s solution be used to measure the concentration of glucose in a solution ?
Use a colorimeter to measure the absorbance of a series of solutions of known concentrations to create a calibration curve Compare the absorbance of an unknown sample to the calibration curve
38
CPAC 11: measuring the concentration of glucose using a calibration curve Outline the procedure of this practical
- make a serial dilution of glucose ranging form 0 to 10mmoldm-3 - place 2cm3 of each of the unknown samples in separate boiling tubes - add 2cm3 of Benedict’s do,union to all the boiling tubes - place the boiling tubes in a water bath at 90degreesC for 4 mins - zero the calorimterbusing a cuvette with distillled water and set to red filter - place the known samples into cuvette and measure the absorbance of each using the calorimeter - make a calibration curve - measure the absorbance of the unknown samples using calorimeter. - Use calibration curve to determine glucose concentrations
39
CPAC 11: measuring the concentration of glucose using a calibration curve How can you increase the accuracy of the estimate of the unknown glucose solutions?
Increase the number of concentrations (at smaller intervals) for the calibration curve within the range of concentrations that the unknown solution belongs in
40
CPAC 12: effect of different variables on species distribution How is percentage cover calculated ?
Use quadrat with squares. Count how many squares the required species is present in Only count a square if more than half of it is covered Calculate the percentage of squares the species is present in
41
CPAC 12: effect of different variables on species distribution Outline the procedure to this practical
- choose an area to take samples from. Use a random number generator to generate 10 sets of coordinates - use 2 tape measures to create a set of axes off which the coordinates can be read - place the quadrat at each of the coordinates, placing the bottom left courier on the coordinate every time - record the percentage cover for the chosen species - at each coordinate a measure of the independent variable should be taken
42
CPAC 12: effect of different variables on species distribution Why should a random number generator be used ?
To avoid bias in random sampling
43
What do each of the species represent in the Hardy Weinberg equation? p2 + 2pq + q2 = 1
p2 = homozygous dominant genotype 2pq= heterozygous genotype q2 = homozygous recessive genotype
44
Give the formula for the chi squared test
x2 = ∑ ([O-E]^2 ÷ E) O= observed value E = expected value
45
How do you determine the critical value for a chi squared statistical test ?
n-1 where n represents the number of phenotypes
46
If you are asked for a 95% confidence level which probability column of the critical value table should you use ?
0.05
47
How can you determine whether or not to accept / reject the null hypothesis using x2 value and critical value for a chi squared test?
If x2 < critical value, accept the null hypothesis If x2 > critical value, reject the null hypothesis **if below accept Ho**
48
What is the expected phenotypic ratio when 2 heterozygotes for 2 genes are crossed ?
9:3:3:1
49
Give the formula for standard deviation
s = √ ∑(x - x̅)^2 ÷ n - 1 x̅ represents the mean x represents an individual value n represents the sample size
50
What is standard deviation a measure of ? What can it be used to calculate?
Variation. And can be used to measure the amount of variation or spread from the mean
51
State the assumptions when using the mark-release recapture method
- No births, deaths or immigrations. - Random mixing of marked individuals within population. - Marking does not affect behaviour of individuals or make them more vulnerable to predators.
52
How are null hypothesis written for the following statistical tests ? Standard deviation and error, chi squared, spearman’s rank
There is no statistically significant **difference** - standard deviation and error, chi squared There is no statistically significant **correlation** - spearman’s rank
53
What are the 2 equations needed to calculate dilution series
C1 x V1 = C2 x V2 V2 = V1 + volume of distilled water to dilute with C1: conc of a stock solution V1: vol of a stock solution to make new conc C2: conc of the solution you’re making V2:vol of new solution you’re making
54
What are the advantages of using a dilution series ?
- Enables you to make solutions with very low concentrations without having to measure out small volumes - improves accuracy
55
What does standard error measure ?
Measure of reliability of means to see if representative of the whole sample
56
If there is no overlap of the bars or values when using standard deviation & error what does this mean ?
That there is a significant difference between the 2 means
57
Give the equation for standard error
SE = s ÷ √n where s is standard deviation n is sample size
58
What does spearman’s rank measure ?
Carried out in order to assess the degree of association between different measurements of the same sample when you have 5-30 pairs of data
59
Give the spearman’s rank correlation coefficient
6 Σdi^2 rs = 1 - ———- n^3 - n n= number of individuals in sample di = difference in ranks of the two measurements made of an individual
60
What can we conclude from a positive/negative rs value for spearman’s rank ?
- A negative value for rs implies a negative correlation - a positive value for rs implies a positive correlation
61
How do you calculate degrees of freedom for spearman’s rank ?
n - 2
62
What can be used if there is only one degree of freedom using chi squared test?
Yates correlation is applied to enhance accuracy of the x2 value

A Level Biology AQA (9 decks)

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