Biology Revision: Practical

Front 1

Some plant material was crushed and shaken with ethanol. Suggest two
improvements that could be made to this method

Back 1

1. weigh known amount plant ;
2. known volume of ethanol;
3. shake for known time ;
4. standardised crushing method ;
5. filtration
6. use same part of plant / same strain / variety of the plant ;

Front 2

Describe how you would prepare an agar plate that would produce this result,
using a sterile Petri dish, sterile nutrient agar, a pure culture of a suitable
bacterium in a bottle and some garlic extract.

Back 2

1. plate pouring ;
2. putting bacteria into molten agar and mix;
3. how garlic extract added (filter paper) ;
4. incubate at stated temperature, <35 ;
5. incubate or appropriate time 1-3 days
6. aseptic precaution e.g. flaming neck of bacteria bottle at beginning ;
7. reducing biohazard described e.g. autoclave used

Front 3

The effectiveness of the extract can be estimated by measuring the size of the
clear zone. Suggest an accurate method for finding the size of the clear zone
in the diagram in (a)(ii).

Back 3

1. graph paper tracing / {mean / average} diameter
/ eq ;
2. count squares / calculate area / eq ;
3. subtract area of {well / paper} / eq ;

Front 4

What do these results suggest about the relationship between the
concentration of garlic extract and its antibacterial effects?

Back 4

1. increasing concentration increases antibacterial
effect / eq ;
2. no effect 25 and below /positive correlation 50
above / eq ;

Front 5

(ii) Compare the antibacterial effect of garlic extract with that of the three
antibiotics.

Back 5

1. garlic better than both tetracycline and
streptomycin / converse / eq ;
2. {not quite as good as / similar to}
chloramphenicol / converse / eq ;
3. credit correct figure manipulation / eq ;

Front 6

What does this information suggest about the validity of the results for the garlic
extract?

Back 6

1. correct ref to clear zone size related to
judgement on validity ;
2. correct ref to relatedness of onion to garlic ;

Front 7

(i) Using the diagram above to help you, draw a similar flow chart summarising
Withering’s research.

Back 7

1. potential substance identified ;
2. trial on a small group of people ;
3. larger group ;
4. dosage refined / ref to near death incident ;
5. publication of treatise ;
6. specific material in passage e.g. how substance identified / numbers in ‘large’ trial

Front 8

Discuss one economic implication of modern drug trialling, compared with
Withering’s methods.

Back 8

1. more expensive / eq ;
2. large numbers / long time / animal testing / legal
costs / equipment qualified ;

Front 9

Identify one similarity and one difference, other than economic factors,
between Withering’s drug trial and a modern drug trial. In each case, give an
explanation for your answer.

Back 9

Similarity
1. discovery / testing on people/ small to start with/
scale up / careful recording of results,
publication/ finding effective dosage / similar
response to safety issues / monitoring patients /
need for replication ;
2. appropriate comments for both protocols ;
Difference
3. animal tests / large scale synthesis / placebo,
double blind trials / sample size ;
4. appropriate comments for both protocols ;

Front 10

Using all the information in Figures 1, 2 and 3, evaluate the benefits and risks
to humans of lowering blood cholesterol with statins.
There will be up to 2 marks awarded for the quality of spelling, punctuation
and grammar and the use of technical terms in your answer to this question.

Back 10

1. people who take statins have muscle problems ;
2. MP1 qualified e.g. named one/ relative incidence
of different ones / wide range of problems / most /
57% of people have muscle problems ;
3. raised cholesterol causes increased CVD /
correlation / converse / eq ;
4. v low ch increase death rate from all causes/ eq ;
5. v high ch increase death rate from all causes / eq ;
6. but not so with all mortality / low and high
cholesterol leads to increased total mortality / eq ;
7. lowering cholesterol (too much) is an overall risk in
men ;
8. from v low to medium cholesterol increase risk of
death from CVD / eq ;
9. from v high to medium cholesterol increases risk of
death from CVD /eq ;
10. ref to in men in relation to fig 2 and/or ref to in
women in relation to fig 3 ;

Front 11

Suggest how the information that you have been given about statins,
cholesterol and CVD might be expanded upon. Consider what further
questions you might want to ask, and where you might look for answers.
(3)
What further questions you might want to ask

Back 11

1. other side effects of statins than muscle problems;
2. data for other age / children ;
3. other causes of CVD ;
4. data on women to do with having babies;
5. comparative cost of treatment vs consequences ;
6. data on effect of cholesterol on named conditions other than CVD ;
7. gender of people with muscle problems ;
8. search engine ;
9. library qualified / journal qualified ;

Front 12

Suggest a source of information about the effects of statins on CVD that
might be unreliable or biased.

Back 12

drug company websites / sites related to scientists
(e.g. their own / institution where they
work/worked) who have big stake in the
cholesterol hypothesis / government sites where
promoting this hypothesis / any appropriately
explained alternative / website or other source
saying things without refs ;

Front 13

how to soften onion root?

Back 13

use hydrochloric acid 盐酸

Front 14

how to make mitosis visible?

Back 14

acetocarmine

Front 15

why use iron to chop the root tip into tiny pieces?

Back 15

Iron in the razor blade and scalpel and dissecting needle reacts with the acetocarmine stain to give a better staining reaction

Front 16

how to dry tiny pieces of root tip?

Back 16

blotting paper

Front 17

how to crushing 3g garlic with 10 cm3 industrial alcohol?

Back 17

using pestle & mortar

Front 18

how to dry the 0.1% of the extract of garlic with industrial alcohol?

Back 18

using pipette and drop it on sterile filter paper disc

Front 19

how to incubate?

Back 19

close petri dish, tape down, incubate the plates for 24 hours at 25C

Front 20

whats the best plant to investigate the fibre strength?

Back 20

stinging nettle

Front 21

how to water retting fibres?

Back 21

place it in a bucket of cold water for 1 week, then remove the stems and softened tissues, dry the fibres

Front 22

where do you hang the fibres with cotton thread on the end of the fibre

Back 22

clamp stand boss

Front 23

how to measure the strength?

Back 23

attach a newton-meter at the bottom and gently pull on the newton-meter until the fibre snaps. the weigh the fibre can take before it snaps is a measure of the tensile strength of the fibre

Front 24

how to get a cell with totipotency?

Back 24

dampen the cotton wool with water and place in plastic tray, spinkle some seeds onto the cotton wool and cover it with transparent cling film. place it in a light, warm place to germinate. use the light bank as a light source. leave it for 3-4 days.

Front 25

how to make an agar?

Back 25

measure 2.5g agar powder into a beaker and add 250 ml distilled water. boil and stir gently with a glass rod until all the agar powder has dissolved. pour the molten agar into several test tubes. let them cool and solidify.

Front 26

which part is the totipotency explants? how to get it?

Back 26

cut off top of seedlings just below the shoot apex with scissors as explants.

Front 27

what you use to touch the onion root to see if it has been softened in the hydrochloric acid?

Back 27

use dissecting needle

Front 28

1mm = ? um

Back 28

1000

Front 29

explain why staining is necessary in this preparation

Back 29

because in a cell that is not actively dividing the chromosomes cannot easily be identified as individual structures. they are translucent to both light and electrons so they cannot easily be seen. when the cells starts to actively divide the chromosomes condense, they become much shorter and denser. they can take up stains very readily and individual chromosomes can be identified.

Front 30

risk assessment for practical on the antimicrobial

Back 30

1, keep alcohol (inflammable) away from naked flames
2, do not open petri dishes containing growing microorganisms
3, use aseptic techniques
4, only dispose of used petri dishes after they have been autoclaved

Front 31

how to make sure something is sterile?/aseptic?

Back 31

autoclave

Front 32

how to make sure that in "antimicrobial " is accurate?

Back 32

1, same size discs
2, same amount of ingredient
3, 10 mol of industrial alcohol
4, use forcep not hands

Front 33

risk in fibre strength?

Back 33

1, wear eye protection and gloves when handling unretted nettles
2, wash hands after handling the soaked fibres
3, when testing fibres to breaking point, make sure the loads on the material can fall without causing injury

Front 34

accuracy of fibre strength investigation?

Back 34

1, 10 cm length fibre
2, newton-meter starts at zero
3, choose approximately same richness of fibre
4, same length same diameter
5, same species of coconut
6, age, type of coconut young fruit

Front 35

what's to control in fibre strength investigation?

Back 35

temperature, humidity, other relevant factor

Front 36

risk in totipotency investigation?

Back 36

wear eye protection and care when boiling and pouring agar

Front 37

accuracy of totipotency?

Back 37

1, seedling from the same species
2, no microrganisms in the agar
3, provide all optimum conditions

Front 38

aseptic techniques

Back 38

1, all apparatus (petri dishes, pipettes, flasks, etc) must be sterilised by autoclaving at 121 c for 15 minutes at 103 kPa, or by irradiating with ultraviolet rays
2, sterile the culture medium by autoclaving
3, wipe the bench / work surfaces with 70% ethanol before and after work
4, flame the necks of bottles to prevent air-borne contamination
5, flame wire loops and forceps before and after use or sterilise by dipping in ethanol
6, lids of containers should not left on benches
7, petri dishes opened slightly during operation to avoid contamination
8, cultures after study and contaminated must be autoclaved / sterilised before disposal or reuse

Front 39

explain why it is important to use equal-sized cylinders of beetroot in this experiment

Back 39

same amount/volume of pigment, same surface area, number of cells on surface

Front 40

state the independent variable in beetroot experiment

Back 40

temperature

Front 41

describe how the degree of redness could be measured

Back 41

colorimeter (or description) ;

Then any two from
• shake before measurement
• use of appropriate colour filter
• zeroing against blank
• clean cuvettes
• wiping cuvettes
• transparent side REJECT smooth side
• measure absorbance / transmission
• enough liquid to allow light go through ;;

OR

comparison of colour ;

Then any two from
• with {known / chart / standard} samples
• comparing tubes by looking down and adding water until same and measurement is depth
• convert to numerical ;;

Front 42

name other variables in beetroot experiment. in each case, describe how the variable could be controlled.

Back 42

1. volume of water in the boiling tube;
2. suitable method e.g. measuring cylinder, pipette;

3. rinsing ;
4. until clear / for fixed time for all ;

5. similar {variety / density / eq} of beetroot ;
6. method to ensure same variety e.g. same beetroot ;

7. pre-treatment e.g. storage;
8. use same part of beetroot; detail e.g. cut from middle, peeling ;

Front 43

use the graph to describe and explain the pattern of results. (temperature&redness). 0-10/20 falls, 10/20 to 40 flat/varies little above 40 to 60 steep rise. above 60 falls/levels off

Back 43

1. freezing / condensation effect at low temperature explained ;
2. effect of temperature on membrane permeability ;
3. effect of temperature on membrane component ;
4. {all / as much} pigment as possible gone at 60 °C / idea of high temperature destroys pigment;

Front 44

state two ways in which the reduction in the incidence of Tay-Sachs disease in certain groups of people might have been brought about.

Back 44

1. pre-implantation screening of embryos to select healthy embryos;
2. fetal screening, followed by abortions;
3. adult screening, followed by voluntary / statutory ban on marriage / reproduction, between carriers;

Front 45

nearly all strategies designed to help with genetic disorders have ethical implications. choose one of the methods you have mentioned and discuss the ethical implications of this method

Back 45

• invasive procedure
• elimination / disposal / storage of unused embryos / right to life
• eugenics / designer babies / discrimination
• who should have access
• high cost

(false positives)
• distress - abortion not justified
• distress - worry about baby / not having children when not a problem
• distress – about abortion that was not needed

(false negatives)
• shock of diseased baby born
• false confidence

Front 46

make suggestions as to how the information about genetic screening that you have been presented with might be expanded upon. consider what further questions you might want to ask, and where you might look for answers.

Back 46

For example
• what research is being done on treatments for TSD
• what is gene therapy
• what progress on gene therapy (in relation to named diseases)
• is it available

internet search engine / scientific journals / magazines / reference to specialist library / reference to relevant experts;

Front 47

explain why it is important to use equal-sized cylinders of beetroot in this experiment

Back 47

same amount/volume of pigment, same surface area, number of cells on surface

Front 48

state the independent variable in beetroot experiment

Back 48

temperature

Front 49

describe how the degree of redness could be measured

Back 49

colorimeter (or description) ;

Then any two from
• shake before measurement
• use of appropriate colour filter
• zeroing against blank
• clean cuvettes
• wiping cuvettes
• transparent side REJECT smooth side
• measure absorbance / transmission
• enough liquid to allow light go through ;;

OR

comparison of colour ;

Then any two from
• with {known / chart / standard} samples
• comparing tubes by looking down and adding water until same and measurement is depth
• convert to numerical ;;

Front 50

name other variables in this experiment. in each case, describe how the variable could be controlled.

Back 50

1. volume of water in the boiling tube;
2. suitable method e.g. measuring cylinder, pipette;

3. rinsing ;
4. until clear / for fixed time for all ;

5. similar {variety / density / eq} of beetroot ;
6. method to ensure same variety e.g. same beetroot ;

7. pre-treatment e.g. storage;
8. use same part of beetroot; detail e.g. cut from middle, peeling ;

Front 51

use the graph to describe and explain the pattern of results. (temperature&redness). 0-10/20 falls, 10/20 to 40 flat/varies little above 40 to 60 steep rise. above 60 falls/levels off

Back 51

1. freezing / condensation effect at low temperature explained ;
2. effect of temperature on membrane permeability ;
3. effect of temperature on membrane component ;
4. {all / as much} pigment as possible gone at 60 °C / idea of high temperature destroys pigment;

Front 52

state two ways in which the reduction in the incidence of Tay-Sachs disease in certain groups of people might have been brought about.

Back 52

1. pre-implantation screening of embryos to select healthy embryos;
2. fetal screening, followed by abortions;
3. adult screening, followed by voluntary / statutory ban on marriage / reproduction, between carriers;

Front 53

nearly all strategies designed to help with genetic disorders have ethical implications. choose one of the methods you have mentioned and discuss the ethical implications of this method

Back 53

• invasive procedure
• elimination / disposal / storage of unused embryos / right to life
• eugenics / designer babies / discrimination
• who should have access
• high cost

(false positives)
• distress - abortion not justified
• distress - worry about baby / not having children when not a problem
• distress – about abortion that was not needed

(false negatives)
• shock of diseased baby born
• false confidence

Front 54

make suggestions as to how the information about genetic screening that you have been presented with might be expanded upon. consider what further questions you might want to ask, and where you might look for answers.

Back 54

For example
• what research is being done on treatments for TSD
• what is gene therapy
• what progress on gene therapy (in relation to named diseases)
• is it available

internet search engine / scientific journals / magazines / reference to specialist library / reference to relevant experts;