Biology Unit 3 Edexcel Cram Notes o2m1h

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

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 ;

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.

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

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

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

1. increasing concentration increases

effect / eq ; 2. no effect 25 and below /positive correlation 50 above / eq ;

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

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 ;

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

1. correct ref to clear zone size related to

judgement on validity ; 2. correct ref to relatedness of onion to garlic ;

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

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 age e.g. how substance identified / numbers in ‘large’ trial

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

1. more expensive / eq ;

2. large numbers / long time / animal testing / legal costs / equipment qualified ;

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.

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 ;

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 in your answer to this question. statins have muscle problems ; 2. MP1 qualified e.g. named one/ relative incidence

1. people who take

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 ;

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 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 ;

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

how to soften onion root?

use hydrochloric acid 盐酸

how to make mitosis visible?

acetocarmine

why use iron to chop the root tip into tiny pieces? Iron in the razor blade and scalpel and dissecting needle reacts with the acetocarmine stain to give a better staining reaction

how to dry tiny pieces of root tip?

blotting paper

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

using pestle & mortar

how to dry the 0.1% of the extract of garlic with industrial alcohol? sterile filter paper disc

how to incubate?

using pipette and drop it on

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

whats the best plant to investigate the fibre strength? stinging nettle

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

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

how to measure the strength? 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

how to get a cell with totipotency? 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.

how to make an agar? 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.

which part is the totipotency explants? how to get it? apex with scissors as explants.

cut off top of seedlings just below the shoot

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

use

1mm = ? um

1000

explain why staining is necessary in this preparation 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.

risk assessment for practical on the antimicrobial flames

1, keep alcohol (inflammable) away from naked

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

how to make sure something is sterile?/aseptic?autoclave

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

1, same size discs

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

risk in fibre strength?

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

accuracy of fibre strength investigation? 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

what's to control in fibre strength investigation? temperature, humidity, other relevant factor

risk in totipotency investigation?

accuracy of totipotency?

wear eye protection and care when boiling and pouring agar

1, seedling from the same species

2, no microrganisms in the agar 3, provide all optimum conditions

aseptic techniques 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

explain why it is important to use equal–sized cylinders of beetroot in this experiment amount/volume of pigment, same surface area, number of cells on surface

same

state the independent variable in beetroot experiment temperature

describe how the degree of redness could be measured 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 ;;

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

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 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;

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

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 • 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

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. 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;

explain why it is important to use equal–sized cylinders of beetroot in this experiment amount/volume of pigment, same surface area, number of cells on surface

same

state the independent variable in beetroot experiment temperature

describe how the degree of redness could be measured 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 ;;

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

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 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;

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

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 • 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

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. 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;