1
Q
What is the function of a stage
micrometer?
A
To calibrate an eyepiece graticule so that
it can be used to make measurements.
2
Q
How is an eyepiece graticule calibrated?
A
Select the desired magnification and objective. Place the
stage micrometer on the stage.
Line up the scales of the micrometer and the eyepiece
graticule.
Count the number of divisions on the eyepiece graticule
equivalent to each division on the stage micrometre.
Calculate the length of one division of the eyepiece graticule.
3
Q
Outline the procedure to preparing a
slide.
A
Stain the sample with an appropriate
dye.
Mount the sample on the slide.
Place a cover slip carefully on the slide,
avoiding air bubbles
4
Q
How is magnification calculated?
A
Magnification =
Size of image / Size of object
5
Q
What can be observed when feeling the
walls of the 4 chambers of the heart?
A
The walls of the atria are thinner than the
ventricles, and the wall of the left
ventricle is thicker than the right
ventricle
6
Q
State an observable difference between
veins and arteries.
A
The walls of arteries are thicker, veins
have valves and a larger lumen
7
Q
Why are plant tissues stained before
they are observed?
A
So that different tissues can appear as
different colours to be more easily
identified.
8
Q
List 3 abiotic factors.
A
Light intensity Humidity
Temperature Wind speed
Water supply Day length
Nutrient supply Rainfall
9
Q
List 3 biotic factors.
A
Competition for resources
Predation
Disease
10
Q
How is percentage cover calculated?
A
Use a quadrat with squares. Count how
many squares the required species is
present in. Only count a square is more
than half of the square is covered.
11
Q
Outline the procedure of random
sampling.
A
- Choose an area to take samples from. Use a random number generator to
generate 10 sets of random coordinates. - Use two tape measures to create a set of axes off which coordinates can be
read. - Place the quadrat at each of the coordinates, placing the bottom left corner 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.
Eg. record light intensity using a photometer at each location
12
Q
How can the results of sampling be used to
determine the relationship between the
chosen factor and the percentage cover?
A
Use a statistical test eg. Pearson’s linear
correlation, Spearman’s rank
13
Q
State Simpson’s Index of Biodiversity.
A
D = 1 - [(n / N)2]
14
Q
What is species diversity?
A
Number of different species in a
community and the relative abundance
of each population.
15
Q
What is the advantage of random
sampling?
A
Prevents selective sampling from
causing bias.
16
Q
Outline the procedure of using a transect
for systematic sampling.
A
- Use a measuring tape to make a transect over the area you wish to
sample. - Place quadrats at given intervals along the tape measure (e.g. every 5
metres). The bottom left-hand corner of each quadrat should be
touching the relevant metre mark, and the left-hand edge runs along
the tape measure - Identify the different species in each quadrat using a key and count
the number of each present. Calculate the percentage cover.
17
Q
Which type of graph is used to represent
the distribution of a species along a
transect?
A
A kite diagram.
18
Q
What are the four factors affecting rate of
enzyme reaction?
A
Enzyme concentration
Substrate concentration
Temperature pH
19
Q
How can you measure the rate of
reaction using hydrogen peroxide and
catalase?
A
Measure the volume of oxygen gas
produced in a given time
20
Q
State the word equation for the action of
catalase.
A
Hydrogen peroxide → Oxygen + Water
21
Q
What are the controlled variables of for measuring the rate of enzyme controlled reaction with catalase
A
Enzyme volume and concentration
Substrate volume and concentration
pH
22
Q
State the hazards and safety precautions
involved in measuring the rate of enzyme controlled reaction using Hydrogen peroxide?
A
Hydrogen peroxide is an irritant. Wear eye
protection and avoid contact with skin.
Take care in handling hot water baths, and wash
hands after handling peas/ source of catalase.
23
Q
Outline the procedure to find the effect of
enzyme concentration on rate of reaction
using amylase.
A
- Put drops of iodine solution into each well of a spotting tile.
- Make a serial dilution of amylase to produce several concentrations.
- Add the same concentration and volume of starch to the first boiling tube. At
the same time, start the timer. - Use a dropping pipette to put a drop of this mixture into one of the wells
containing the iodine solution at regular intervals. - Time how long it takes for the colour to no longer turn blue-black.
- Repeat at least 2 more times and calculate the mean time taken.
- Repeat the experiment for each concentration of amylase.
24
Q
What are the controlled variables of enzyme controlled reaction with amylase
A
Temperature
pH
Substrate volume and concentration
Volume of enzyme added
25
What does calorimeter measure?
Absorbance/transmission.
The paler the solution, the lower the
absorbance and higher the transmission,
as more light can pass through the
sample.
26
Outline the procedure to find an unknown
concentration of reducing sugar.
1. Carry out a Benedict’s test on a range of standard solutions of reducing
sugar.
2. Using the colorimeter, measure the percentage transmission for each sample.
3. Plot a graph of transmission against reducing sugar concentration.
4. Carry out a Benedict’s test on the unknown solution and measure the
transmission using the colorimeter.
5. Plot the transmission on the calibration curve, and read off the x axis
(reducing sugar concentration) for the concentration of the unknown solution.
27
What indicates a higher reducing sugar
concentration where carrying out calorimetry
Higher absorbance, lower transmission.
28
What is the function of a potometer?
A device used to measure the rate of
water uptake of a plant, and hence the
rate of transpiration
29
Which factors affect the rate of
transpiration?
Temperature Water supply
Humidity Surface area
Wind speed Presence of cuticle
Light intensity
30
Why must the leafy shoot be cut
underwater?
To prevent air bubbles from forming in
the vascular tissue
31
Why should the cut of the shoot be
slanted?
To increase the surface area available
for water uptake.
32
Outline the procedure of the potometer practical.
1. Set up the potometer.
2. Clamp the capillary tube into the stand. Place the bottom of the
capillary tube into the beaker of water.
3. Smear petroleum jelly around the join to maintain airtight conditions.
4. Leave for 5 minutes for a bubble to be drawn into the capillary tube.
5. Measure the movement of the bubble along the capillary tube in a
certain length of time.
6. Repeat the experiment and change the abiotic variable
33
How is the rate of transpiration
calculated from a potometer
Measure the distance travelled by the bubbles in the
capillary and the radius of the capillary.
Find the volume of water taken up by using πr2
.
Divide the volume by time.
34
How is light intensity controlled during the potometer practical?
By changing the distance between the
lamp and the potometer.
35
How can wind speed be controlled during the potometer practical?
By placing a fan near the potometer with
different speeds.
36
How can humidity be controlled during the potometer practical?
By wrapping a plastic bag around the
plant to maintain a humid environment.
37
What are some limitations of this
method for the potometer practical?
Not all of the water taken up is
transpired, some is used to maintain
turgidity and for photosynthesis
The plant is dying when the stem is cut,
rate of water uptake is lower than normal
38
What is the purpose of chromatography?
To separate different components in a
sample
39
State the factors affecting the rate of
migration of different pigments during chromatography.
Solubility
Mass
Affinity to the paper
40
What is the formula of the RF value?
Distance moved by pigment / Distance
moved by solvent
41
What is the purpose of finding the RF
value of a pigment?
Experimental RF value can be compared to a
standard value in a database to identify the
pigment.
The standard value should be using the same
paper and solvent.
42
Outline the procedure of using
chromatography to separate
photosynthetic pigments.
1. Draw a pencil line 1cm above the bottom of the filter paper.
2. Add some acetone and use the mortar and pestle to grind up the leaf sample
and release the pigments.
3. Use a capillary tube to transfer the pigment onto the pencil line.
4. Suspend the paper in the solvent so that the level of the liquid does not lie
above the pencil line and leave until the solvent has run up the paper to near
the top.
5. Remove the paper from the solvent and draw a pencil line marking where the
solvent moved up to.
6. Calculate the Rf value for each spot.
43
State the hazards and precautions of using chromatography to identify photosynthetic pigments.
Solvents are irritant and flammable.
Keep away from naked flame, wear eye
protection and avoid contact with skin.
Leaf extract may be a biohazard. Wash
hands after use.
44
Why should the final locations of the
pigments be marked?
The pigments may also disappear as the
solvent dries.
45
How can chromatography be used to
separate amino acids?
Same method as leaf extract, except
spray the chromatography paper after
the solvent had run with ninhydrin
solution to stain each residue purple.
46
What is the purpose of gel
electrophoresis?
To separate fragments of DNA. It can be
used for DNA fingerprinting.
47
How does gel electrophoresis work?
It separates DNA fragments by their length. Due to
the negative charge of the phosphate groups in
DNA, it is attracted to the positive electrode (anode),
and shorter fragments move at faster rates. Hence,
the fragments move different distances within a
given time.
48
What are controlled variables in gel electrophoresis?
Voltage applied
Thickness of agarose gel
Temperature
Time allowed for DNA to run
Restriction enzymes used
49
What are restriction endonucleases?
They are a type of enzyme derived from
bacteria that cuts DNA into fragments at
specific restriction sites.
50
Outline the procedure of gel
electrophoresis.
1. Use restriction enzymes to cut the DNA sample.
2. Load into wells near the cathode of the agarose
gel, along with buffer.
3. Apply an electric current and allow the fragments
to separate. Stop the current before the DNA
reaches the end of the gel.
51
Other than DNA, which molecules can
be tested using electrophoresis?
Protein, RNA.
52
State 5 aseptic techniques.
● Wash your hands and disinfect your work area.
● Have Bunsen Burner on nearby to sterilise the air and prevent air-borne
microorganisms settling.
● When opening the bottle of broth, pass the neck over the Bunsen Burner
flame to prevent the microorganisms in the air entering the bottle.
● Only open a petri dish enough to allow you to introduce your desired
organisms.
● All equipment should be sterilised by passing it over the flame before and
after use.
53
Why is bacteria incubated at 25°C?
To prevent the growth of pathogens
(harmful bacteria), which occurs at
higher temperatures.
54
Why are petri dishes incubated upside
down?
To prevent condensation from forming on
the lid and dripping down onto the
bacteria.
55
Outline the procedure to find the effect of
antibiotics on bacteria growth
1. Using a sterile pipette, add the same volume of each antibiotic to a different
Petri dish.
2. Dip an inoculating loop in the broth. Recap the broth bottle.
3. Spread a streak of broth over the agar surface, then close the Petri dish, and
tape it shut. Repeat for the remaining Petri dishes. Label each petri dish.
4. Place the petri dishes in a warm incubator. Leave all the plates for the same
amount of time (e.g. a day) then observe the results.
5. Count the number of colonies that have formed on each plate and record
results in a table. Calculate the mean number of colonies formed for each
antibiotic.
56
How should the controls be set up for The Microbial Techniques PAG?
Two petri dishes with no antibiotic and
two uncultured petri dishes.
57
State the hazards and precautions of the Microbial techniques.
Naked flame: keep away from flammable materials,
tie hair up, wear goggles
Bacteria is a biohazard, use disinfect and wash
hands, dispose of bacteria safely
Disinfectant is flammable, keep away from naked
flame.
58
Why should the lid not be completely
taped to the petri dish?
To allow oxygen to enter the petri dish,
preventing the growth of harmful
anaerobic bacteria.
59
State 2 factors that affect the
permeability of cell membranes
Temperature
Concentration of solvents (ethanol)
60
How is beetroot used to measure the
permeability of cell membranes?
The higher the permeability, the more red
pigment that leaks out into the surrounding
solution within a given time. A colorimeter can
be used to determine the absorbance, hence
concentration of pigment.
61
Outline the procedure to investigate the
effect of temperature on permeability of
cell membrane.
1. Cut beetroot into 6 identical cubes with a scalpel.
2. Place each cube in a different test tube with equal
volumes of distilled water.
3. Place each test tube into water baths ranging from 30-80°
C. Leave for 20 minutes.
4. Filter each solution out into a cuvette and measure the
absorbance.
62
What are the safety hazards involved in
testing the effect of ethanol
concentration on membrane
permeability?
Ethanol is an irritant and is flammable, keep away
from naked flames, wear eye protection.
Keep sharp scalpel away from fingers.
Handle hot liquid with care.
63
What is the effect of temperature on
membrane permeability?
Increasing temperature results in
increase membrane permeability.
64
What is the effect of ethanol
concentration on membrane
permeability?
Increasing ethanol concentration leads to
increased membrane permeability, as
ethanol causes gaps to form in the
membrane.
65
Outline the materials used to measure
the rate of diffusion.
Make agar jelly mixed with phenolphthalein.
Place in HCl and measure the time taken for the
agar jelly to turn colourless.
Change the factor and repeat eg. concentration
of HCL, surface area of agar jelly.
66
What is the effect of concentration on the
rate of diffusion?
Increasing concentration increases the
steepness of the concentration gradient,
hence increasing the rate of diffusion
(decreasing the time taken for the agar jelly to
decolourise).
67
What is the effect of surface area on the
rate of diffusion?
Increased surface area to volume ratio
increases the rate of diffusion.
68
What is Biuret’s test for?
Protein.
69
Outline the procedure to a Biuret test.
1. Add sodium hydroxide solution.
2. Add copper (II) sulphate solution.
3. If the colour changes from blue to
purple, protein is present.
70
What does iodine test for?
starch
71
What is the colour change for a positive
iodine test?
orange brown -> blue black
72
Outline the procedure to the emulsion
test.
1. Add ethanol.
2. Pour solution into water.
3. A white emulsion forms.
73
What does Benedict’s reagent test for?
Reducing Sugars
74
Outline the test for reducing sugars
1. Add equal volume or excess
Benedict’s reagent to a sample and
boil.
2. If positive, colour changes from blue to
red, with a brick-red precipitate.
75
Outline the test procedure for
non-reducing sugars.
1. Add dilute HCl and boil.
2. Neutralise with sodium hydrogen
carbonate.
3. Add Benedict’s reagent and boil.
4. If positive, colour changes from blue to
red, with brick-red precipitate.
76
What is a method to test for glucose
specifically?
Dip the pad of a glucose test strip into the
sample. Colour change will occur if glucose is
present.
Concentration can be found by comparing colour
to a colour standard chart.
77
What is the function of a spirometer?
What is the function of a spirometer?
78
How is tidal volume found using a
spirometer?
It is the distance from peak to trough
when the participant is breathing
normally.
79
How is vital capacity found using a
spirometer?
The distance from peak to trough when
the participant takes a forced deep
breath.
80
What does an upward slope on the
spirometer trace indicate?
Person breathing in.
81
What does a downward slope on the
spirometer trace indicate?
Person breathing out.
82
Outline the procedure to investigating the
effect of exercise on heart rate.
1. Measure the resting heart rate.
2. Do some gentle exercise, such as stepping on and off a step for 5
minutes. Immediately afterwards, measure the heart rate again.
3. Return to the resting position. Measure the heart rate every minute
until it returns to the resting state.
4. Record the time taken to return to normal.
5. Repeat the experiment for different people (e.g. 8 people).
83
How is heart rate measured?
Place your fingers on your forearm.
Count the number of beats in 15
seconds and multiply that by 4 to get the
number of beats per minute
84
Which test can be used to test if the
effect of exercise is significant, and why?
T-test, because it is comparing 2 means.
85
What is phototropism
The orientation of a plant in response to
light.
86
What should be the controlled variables
when investigating phototropism?
Temperature, nutrient concentration,
humidity, light intensity
87
How should the shoots be prepared?
1: Cover tips with foil
2: Cover base with foil
3: Leave without foil
88
What is geotropism?
The growth of plants in response to
gravity.
89
Outline the procedure to investigating
geotropism.
1. Line three petri dishes with moist cotton wool.
2. Space out 10 cress seeds on the surface of the wool. Press them down in the
wool slightly.
3. Put a lid on each dish. Wrap the dishes in foil to prevent light reaching the
seeds. Leave the dishes where the temperature is constant and warm.
4. Set up the dishes so they’re placed at different angles: 90, 45, 0 degrees.
5. Leave the seeds for 4 days.
6. After 4 days, unwrap each dish and note the direction of the shoot and root
growth of cress seedlings. Record in a table.
90
What are the controlled variables for
investigating geotropism?
Volume of water provided
Mass of cotton wool Number of seeds
Exposure to light Species of seed
Temperature Time allowed for growth
91
What is the function of auxin in plants?
It stimulates cell elongation for growth,
and has a role in apical dominance.
92
What is apical dominance?
Where the main stem inhibits the growth
of lateral buds.
93
Outline the procedure to investigate the
effect of auxin.
1. Select 30 plants similar in height, mass and age. Count the number of
side shoots growing from the main stem.
2. Apply a paste with auxin to 10 plants, apply a past without auxin to
another 10 plants, and leave the remaining 10 as they are.
3. Allow 6 days for the plants to grow.
4. Count the number of side shoots that have grown from the main stem
94
What are the controlled variables of finding the affects of auxin?
Age, height, mass of plant
Species of plant Temperature
Light intensity
Water
95
What is the role of gibberellins in plants?
They have a role in germination and
stem elongation
96
Outline the procedure to find the effect of
gibberellin on plant stem elongation.
1. Select 40 plants of similar height, age and mass.
2. Leave 20 to grow, and water the other 20 with a dilute gibberellin
solution.
3. Leave the plants to grow for 28 days.
4. Measure the length of the stem of the plants every 7 days. Calculate
the mean stem length.
97
Describe how a respirometer works.
It is a chamber connected to a manometer tube
with a drop of manometer fluid. As the organism
in the chamber respires and uses oxygen, the
pressure decreases and the liquid moves in the
manometer tube.
98
How is the rate of respiration calculated
using data from the respirometer?
Rate =
Volume of oxygen used / mass / time
99
What are the controlled variables of measuring the rate of respiration using a respirometer?
Mass of organism Time
Temperature
Mass of soda lime
Apparatus must be airtight, and replace air
between each set-up
100
What does the change in volume in the
manometer tube indicate?
The volume of oxygen consumed by the
organism.
A-Level OCR Biology
flashcards
Decks in class (12)
# Cards
-
2.1 Foundations in Biology194
-
3.1 Exchange and Transport106
-
4.1 Communicable disease, disease prevention and immune system57
-
4.2 Biodiversity94
-
5.1 Communication and Homeostasis241
-
5.2 Energy for Biological Processes57
-
6.1 Genetics and Evolution109
-
6.1.3 Chi squared and Evolution15
-
6.2 Cloning and Biotechnology51
-
6.3 Ecosystems35
-
STUFF I AM GETTING WRONG1
-
PAGs100
