CIE Flashcards

1
Q

Describe how the malarial parasite is transmitted.

A

female Anopheles mosquito ; either takes blood meal / AW, from infected person or parasites enter mosquito in blood meal from infected person ;

takes blood meal / AW, from uninfected person ; parasite / pathogen / plasmodia, transferred in mosquito’s, saliva / anticoagulant ; ref. to transfusion malaria / congenital or mother-foetus malaria / needle sharing / needle stick injury for max 1

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2
Q

Explain how using such a vaccine may give long-term immunity to malaria.

A

protein is) antigen ;

following vaccination (clonal) selection for, appropriate / corresponding / specific, B cell ; clonal expansion / divide (by mitosis) (to form B cell clone) ; memory cells ;

on infection by parasite (B cells / plasma cells) secrete antibody ; A immunoglobulin / Ig secondary response (qualified) / higher levels of antibody / rapid production of antibody ; ref. to antigen-antibody specificity ; antibody attaches to, surface protein / antigen, on parasite ; prevents attachment to red blood cell ; A prevents entry into red blood cell

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3
Q

Researchers have been trying to develop a successful vaccine against malaria for about 20 years. Explain why it has proved so difficult to develop such a vaccine.

A

genetic complexity of Plasmodium ; A ref to Plasmodium, being eukaryotic / having many genes many antigens ; many stages in life cycle (within human) ; antigens change / antigenic variation, in different stages ; Plasmodium / parasite, lives within cells ; A antigenic concealment A only briefly free in the blood stream antibodies cannot work against stages within cells

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4
Q

explain why it is difficult to assign some organisms to trophic levels.

A

some animals feed at different (trophic) levels / animals do not obtain all their food from one (trophic) level ; A correct reference to at least two consumer levels animals may feed on different (trophic) levels at different, times / seasons ; some food chains, do not start from primary producers / start from decomposing matter ;

named examples from food web ;

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5
Q

State two factors that are likely to influence the efficiency of energy transfer by herbivorous copepods.

A

proportion of, phytoplankton / copepods, that is digested / some remains undigested ; phytoplankton have cell walls ; proportion that is absorbed after digestion ; loss in, egestion / faeces ; in terms of energy loss in, excretion ; loss or energy loss in, respiration / heat (by copepods) ; availability energy losses in movement / AW ; AVP ; e.g. denser phytoplankton means less energy loss in feeding

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6
Q

Describe how M. tuberculosis is transmitted from an infected person to an uninfected person

A

(infected person) coughs / sneezes / spits / releases sputum / breathes out / exhales ; A releases mucus R talks aerosol / droplets / moist air, inhaled / breathed in (by uninfected person) ;

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7
Q

Suggest why fatality ratios for TB are higher in some of the countries than in others.

A

poor / dense / overcrowded, housing / accommodation ; low protein diets linked to lowered immunity ; not, diagnosed / treated, early enough ; DOTS / described, not used ; lack of vaccination / vaccinations ineffective ; antibacterial drugs / antibiotics / AW, not available / too expensive ; medical services not available, qualified e.g. in rural areas / AW ; idea of TB, linked to HIV/AIDS / opportunistic disease ; MDR – TB / XDR – TB / not completing the course of antibiotic treatment increases resistance ; no effective antibiotics to use ; no facilities for isolating people ; lack of, testing / treatment of, cattle / milk ; A unpasteurised milk difficulty in obtaining reliable data / AW ;

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8
Q

ecosystem

A

all the organisms and the physical factors that influence them in an area, such as a forest

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9
Q

habitat

A

a place where an organism lives

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10
Q

community

A

all the organisms / plants and animals / populations / AW, in the ecosystem / forest / place / area / habitat ;

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11
Q

niche

A

role of organism in an ecosystem

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12
Q

population

A

all the organisms of the same species in an ecosystem at the same time

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13
Q

suggest why there are few predators, such as jaguars and harpy eagles, in the forest ecosystem even though there are many producers, such as trees.

A

predators are, secondary consumers / tertiary consumers / top carnivores ; (population, size / number of) predators limited by numbers of prey / sloths / AW ; energy loss, between trophic levels / along food chain / inefficient energy transfer ; detail e.g. only 10% transfer / respiration / heat / movement / excretion / inedible parts / egestion / to decomposers; (prey numbers small so) competition for, food / prey ; predators hunted by humans ; habitats / areas, of predators destroyed ;

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14
Q

reasons for decreased mortality rates

A

decreasing mortality rate because earlier diagnosis (so fewer die) ; improved, health care / treatment (extends life) ;

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15
Q

Explain how it is possible to reduce the number of deaths during a cholera epidemic in countries such as those in West Africa.

A

provide, boiled water / bottled water / sterile water ; A valid description of method to, remove / kill, bacteria provide, oral / intravenous, rehydration therapy / ORT ; A ORS (contains) glucose and, salts / electrolytes ; absorption of salts helps to absorb glucose ; (absorption of salts) increases water uptake, by osmosis / AW ; deaths usually caused by (rapid) dehydration ; idea of rapid provision (of, ORT / medical supplies / personnel) ; provide antibiotics (for severe cases) ; safe sewage disposal, qualified ; R sewage treatment plants

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16
Q

Explain why cholera is unlikely to be transmitted in developed countries.

A

transmission cycle is broken ; sewage treatment plants / mains drainage ; human faeces do not come into contact with drinking water supply ; water treatment plants ; A drinking water is, chlorinated / treated, to kill bacteria ; drinking water is piped to homes ;

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17
Q

Define the term term commnicable disease

A

caused by pathogen, transmissible / communicable / contagious / transferable / passed from
one person to another ;

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18
Q

Explain why malaria is found in mostly sub Saharan africa, but TB is found everywhere.

A

Anopheles / mosquito / vector, survives / breeds / lives, within the tropics / in hot and
humid areas ; ora
2 Plasmodium / pathogen / parasite, needs to reproduce within the mosquito (at
temperatures above 20°C) ;
3 eradicated in some countries outside the tropics ;
4 ref. to LEDCs and, poor / non-existent, mosquito control programmes ;
5 mosquitoes resistant to, DDT / insecticides / pesticides ;
6 Plasmodium resistant to, drugs / chloroquine / other named drug ;
7 TB is transmitted, by, droplets / coughing / sneezing ; A in the air
8 no vector / no mosquito / no requirement for hot or humid conditions ;
9 ref. to, HIV infection / lower immunity / immunocompromised ;

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19
Q

Explain how vaccination provides immunity as an important part of programmes to control and eradicate infectious diseases

A

active immunity ;
2 vaccine contains, antigen(s) / pathogen / microorganism / named type ;
3 (primary) immune response ;
4 B lymphocytes / B cells / plasma cells, synthesise / produce / secrete / release,
antibodies ;
5 ref. to T helper cells (enhancing humoral response) ;
6 clonal selection / described ;
7 specific, (T / B) lymphocytes / antibodies ; A ‘particular’ / AW
8 memory cells, remain (in circulation) / give long-term immunity / give immunological
memory / AW ;
9 fast(er) second(ary) response ;
10 ref. to boosters / AW ;
11 immunised person cannot spread disease to others ;
12 herd immunity / unimmunised people are safe(r) ;
13 surveillance of population for signs of disease / when there is an outbreak ;
14 ref. to ring immunity / AW ;

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20
Q

Suggest the advantages gained by legumes of having Rhizobium living in their roots

A

provide source of, fixed nitrogen
/ usable nitrogen / organic nitrogen / amino acids / ammonia
/ ammonium ions / AW ; R nitrate
ref. to protein production in legume ;
legume can, colonise / grow in, nitrogen / nitrate, deficient or poor soils ;
A not dependent on nitrate in soil
compete successfully with non-leguminous plants ;

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21
Q

Suggest two reasons for the differences shown in estimated life expectancy without HIV/AIDS between the different African countries.

A

more educated population ; in context of healt
2 better/greater access to, health care/AW ;
3 higher level of preventive medicine ; e.g. immunisation programmes
4 better diet ; A ref. to less malnourished
A ref. to access to food supplies
5 greater access to, therapeutic medicines/drugs ; A antibiotics
6 better/less overcrowded, housing/living conditions ;
7 better, sanitation/sewage treatment ;
8 greater access to uncontaminated drinking water ;
R clean water unqualified
9 fewer, fatal diseases/AW ;
10 ref. to effects of, civil war/war ;
11 ref. to natural disaster

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22
Q

List two factors in the prevention and control of HIV/AIDS that would help to improve average life expectancy in the African countries

A

anti HIV drug therapy/AW ;
2 ref. to treatment of AIDS-related diseases ;
3 ref. to education to prevent, transmission/spread ;
4 use/provide free, condoms/femidoms ; A dental dams
5 avoid promiscuity ; A one sexual partner
6 HIV mothers avoid breast feeding ;
7 heat treat/screen, blood (for transfusion) ;
8 needle-exchange schemes/AW ; A ref. to sterile syringes
9 use of sterile equipment, qualified e.g. in surgery/tattooing/piercing ;
10 testing for HIV status/contact tracing ;
11 ref. to vaccine development ;

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23
Q

Outline the events that occur in a newly-infected person, which lead to the production of antibodies to HIV.

A

primary/immune, response ;
2 ref. specificity; in correct context
3 (HIV/virus) antigens ;
4 antigen presentation/antigen presenting cell/APC/described ;
5 clonal selection/described ; e.g. recognition of/binding to, antigen by, B-lymphocyte
6 sensitisation/activation/described ; e.g. cell growth or cellular changes
7 clonal proliferation/formation of clone/mitosis/cell division/AW ;
8 B-lymphocytes/B-cells/plasma cells, synthesise/produce/secrete/release, antibody ;
9 T(helper)-lymphocyte response described ; e.g. cytokine production

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24
Q

Suggest how a change in the gene can lead to the different enzymes being made

A

altered, (mRNA) codon(s)/triplet(s) ; A named type of mutation
changed/AW, amino acid(s) ;
ref. to effects of stop codon ; e.g. shortened polypeptide chain
different, primary structure/described ;
A ref. to differences in, transcription/translation
ref. to different properties of, R group/side chain (of normal v replaced amino acid) ;
altered tertiary structure/AW ; A different R group interactions
A change/loss of, active site
idea of globular to fibrous change/hydrophilic R groups no longer to outside ;

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25
Q

what a producers

A

photosynthetic/autotrophic/fix carbon/ have chlorophyll

at the start of the food web/at the first trophic level/the source of energy to rest of
food web

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26
Q

Describe one method of controlling the spread of malaria by targeting its vector and explain its effect

A

any named biological control method e.g B. thuringiensis ;
kills mosquito larvae ;

use of insecticides ;
kills (adult) mosquitoes ;

elimination of standing water ;
removes, mosquito breeding sites/egg-laying areas ;

use of oil on water ;
prevents maturation of/kills, mosquito larvae ;

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27
Q

Suggest how HIV infection may have led to an increase in malarial infections in sub Saharan africa

A

HIV, infects/AW, T (helper)–lymphocytes/T-cells ;
qualified ref. to immune system ;
(HIV and) malaria may be contracted via blood transfusion ;
ref. to reduced number of workers so malaria prevention not carried out

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28
Q

Explain what is meant by the term nitrogen fixation

A

conversion of/AW, nitrogen (gas)/N2 ; in context of atmospheric nitrogen
(to) ammonium (ions/compounds)/NH4
+ /amino acids ;

further detail ; e.g. nitrogenase (enzyme)/ref. conversion from unreactive (nitrogen) to
reactive (compound)/reduction of nitrogen/ATP required/anaerobic conditions required for
enzyme function

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29
Q

Explain the importance of this process in making nitrogen from animals available for uptake by plants

A

) supplies, ammonia/ammonium ions, for, nitrifying bacteria/nitrification ;
ammonia/ammonium ions, converted/oxidised/AW ;
to nitrite ;
to nitrate ;
Nitrosomonas /Nitrobacter ; in correct context
ref. nitrate useable form for plants ;

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30
Q

State the trophic levels to which each of the organisms named in the passage belong and outline the energy losses that occur in the food chain.

A

energy losses in
respiration ;
heat loss, qualified ; e.g. heat loss, from digestion / movement / metabolism
heat loss in respiration = 1 mark
indigestible parts ; A named, e.g. cellulose
inedible parts ;
excretion ; A named excretory products
egestion ; I waste
death, not eaten

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31
Q

State one factor, other than drug therapy, that contributed to the steady decrease in the number of new cases of tuberculosis

A

ref. (BCG) vaccine / vaccination programme ;
improvements in housing conditions / less overcrowding (housing) / better ventilated
homes ; R better standards of living unqualified
earlier detection / mass, chest X-ray / screening ; i.e. in preventing spread
improvements in diet (leading to better immune system) / AW ;
improved awareness of, transmission / AW ; R better education unqualified
contact tracing / explained ;
ref. testing / treating, cattle / milk ;

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32
Q

Outline three reasons why, in many developed countries, the number of new cases of tuberculosis is now increasing

A

development of antibiotic resistance (by organism) ; A drug resistance
R immunity
ref. impact of HIV infection ;
higher rate of immigration from countries with high incidence / AW ;
increase in tourism to countries with high incidence ;
reduced surveillance leading to undetected cases (and hence spread) ;
(detected cases, MDR) unwillingness / AW, to maintain drug regimen / AW ;
ref. to vaccination programmes no longer taking place ;
ref. to poor / overcrowded, housing (in cities) / AW ; must be in context of developed
countries

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33
Q

Streptomycin was the first antibiotic to be discovered that was effective against the pathogen that causes tuberculosis. Streptomycin causes the death of the pathogen by binding to ribosomes and inhibiting protein synthesis.
(i) Suggest two ways in which streptomycin acts at ribosomes to inhibit protein synthesis

Streptomycin does not harm mammalian cells.
Suggest an explanation for this.

A

binding of tRNA prevented ;
(so) no anticodon-codon binding ;
peptide bond formation prevented ;
mRNA attachment prevented ;
inhibition of enzymes involved in translation ;
ribosome movement along mRNA, hindered / prevented ;
inhibits association of large and small subunits / AW

also cell surface membrane impermeable ;
degraded, before entry into / within, the cell ;
broken down by enzymes ;
eukaryotic / 80S (22nm) / larger / different, ribosomes / ribosome structure

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34
Q

why is In agriculture, canglucose + nitrate -> water + carbon dioxide + nitrogen be undesirable

A

nitrate required for, amino acid / protein / nucleic acid, production in plants ;
A other relevant named N-containing biochemicals
nitrogen (gas) not useable form for (most) plants ;

removal of nitrate
slows / AW, growth of plants ; A reduces crop yield A plants need nitrates for growth
decreases fertility of soil / fertilisers need to be added to soil ;

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35
Q

For Examiner’s Use
6 In anaerobic soil, bacteria, such as Pseudomonas stutzeri, can use nitrate ions (NO3–) as a source of oxygen for their respiration. The word equation below summarises the process

Suggest how bacteria, such as Pseudomonas stutzeri, can be used in the process of purifying water for drinking

A

(ii) P. stutzeri / bacteria, can be (added to the water and) used to, remove nitrate / carry out
denitrification ;
detail ; e.g. use of filter bed
ref. to leave for sufficient time to remove nitrates
nitrogen escapes to air

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36
Q

In recent years there has been an increase in flooding of agricultural land worldwide.
Explain why crop yields are often significantly reduced even after the flood water has drained away.

A

1 air / oxygen, will not get into soil ;
2 lack of oxygen reduces uptake of ions by plants / AW ;
3 ref. saprobiotic bacteria and fungi / nitrifying bacteria / (some) nitrogen fixing bacteria,
are aerobic ;
4 ref. reduced populations (of bacteria in mp 2) ;
5 example of effect on nitrogen cycle ;;
6 e.g. slower rate / AW, of decomposition / decay
nitrogen fixation cannot occur (as rapidly)
nitrification cannot occur / nitrate will not be produced / less nitrate produced
(more) denitrification will occur
7 crops / plants, will use up remaining nitrate ;
8 ref. leaching of, nitrates / other nutrients, for growth or (only) low levels of nitrates / other
nutrients, for growth remain in soil ; A ref. leaching reducing soil fertility
9 AVP ; e.g. named example of another nutrient, with role
will take time to, recover nitrate levels / resume nitrogen fixation ;
fertilisers (previously) applied washed away ;

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37
Q

Antibiotic resistance is a serious worldwide problem.
Suggest how antibiotics can be used effectively to avoid the development of widespread
resistance in bacteria.

A

do not prescribe for viral diseases ;
2 only use when necessary / do not overprescribe ;
3 only available on prescription / not available ‘over the counter’ ;
4 people must, complete the course / take as instructed ;
R take a long course
5 test to find out which is most appropriate antibiotic to use ;
A use most, appropriate / effective, antibiotics
A use narrow-spectrum antibiotics
6 details of sensitivity test ;
7 rotate / AW, antibiotics / use in combination ; R use many antibiotics
8 do not use same antibiotics for humans and animals ;

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38
Q

The amoeboid cells of D. discoideum feed on protein-rich material and break it down
to form ammonium ions (NH4
+). The cell membranes of D. discoideum have transporter
proteins that are responsible for the excretion of ammonium ions.
Describe what happens to the ammonium ions excreted by D. discoideum into the soil.

A

1 nitrification / nitrifying / oxidation ;
2 ammonium ions to nitrite ions ;
3 nitrite ions to nitrate ions ; A one mark for ammonium to nitrate
4 one named microorganism in correct context
Nitrosomonas / Nitrobacter ; R Rhizobium
5 ammonium / nitrate / AW, absorbed by plants / leached / AW ;

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39
Q

The amoeboid cells of D. discoideum feed on protein-rich material and break it down
to form ammonium ions (NH4
+). The cell membranes of D. discoideum have transporter
proteins that are responsible for the excretion of ammonium ions.
Suggest why a transporter protein is required for the removal of ammonium ions from
D. discoideum.

A

ammonium ions are (positively) charged ; A hydrophilic / polar / water-soluble
2 cannot pass through, phospholipid bilayer / membrane ;
either
3 active transport ;
4 moved against concentration gradient ;
or
3 facilitated diffusion ;
4 moves down its concentration gradient ;

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40
Q

Explain how the virus that causes measles is transmitted

A

(infected) person, sneezes / coughs / talks / breathes out, (airborne)
droplets / aerosol/ moist air ;
inhaled/ inspire/ breathed in, by uninfected, person ;

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41
Q

Explain the functions of variable region

A

binds / attaches / combines, to antigen ;

ref. to specificity ;

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42
Q

Explain the functions of disulphide bond

A

holds, polypeptides /heavy chains / long chains, together ;

maintains, tertiary / quaternary / 3D, structure/ shape ;

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43
Q

Explain the functions of constant region

A

binds to, receptors / cell (surface) membrane, on, phagocytes / macrophages ;
antigen, marking/ tagging, for, phagocytosis / macrophage action ; AW

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44
Q

Antibiotics are prescribed to people who have HIV/AIDS for the treatment of secondary
infections, but not to treat the HIV infection.
Explain why this is so.

A

antibiotics are not effective against HIV or viruses / antibiotics are effective against,
(named) bacteria/ bacterial disease ;
A fungi/ protoctists / protists / malaria
R antibiotics prevent infection
2 idea that viruses have no, sites / targets, where antibiotics can work ;
3 viruses have no, cell walls /ribosomes / cell membranes ;
A have different enzymes
4 viruses are within cells, idea that antibiotics cannot reach them ;
5 people with HIV are more susceptible to bacterial infections /reference to immune
suppression/weak immune system ;

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45
Q

Describe how V. cholerae is transmitted from an infected person to an uninfected person

A

one mark for infected person with contaminated faeces, e.g.
faeces / sewage, contaminates (drinking)water/ cooking utensils / vegetable plots / crops / food ;
A diarrhoea for faeces
R (human) waste unqualified
A ref. to houseflies landing on contaminated faeces

one mark for uninfected person
eating contaminated food/using contaminated utensils / drinking contaminated water ;
A bacteria enters water in context of drinking
R infected food or water
I handling contaminated food
A faecal-oral route for two marks

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46
Q

Explain the importance of nitrogen-fixing organisms, such as in ecosystems

A

provides ammonium (ions)/ ammonia/nitrogen(ous) compounds /fixed nitrogen/ organic
nitrogen ; A organic compounds
R nitrate / nitrite
R nitrate/ nitrite, and ammonia
A formulae NH3 /NH4
+
if only a formula is used then it must be completely correct
accept the following in context of plants / animals
for synthesis of amino acids / nucleotides ;
synthesis of protein/ nucleic acids /DNA/RNA ;
proteins required for, growth/ enzymes / tissue repair/AW ;
nucleic acids for storage of genetic information/AW ;
idea of offsets loss of, (fixed) nitrogen/ nitrate ions ;
reduces effect of (fixed) nitrogen as a limiting factor (for growth) ;

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47
Q

Explain what is meant by the term non-self antigen.

A

non-self
foreign/AW ; A ref. to epitope(s) I pathogen /organism
antigen
macromolecule/(glyco)protein/ carbohydrate/ polysaccharide/ oligosaccharide ;
stimulates /AW, an immune response/production of antibodies ;
A results in formation of antigen-antibody complexes
A other described events in an immune response

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48
Q

Outline how B-lymphocytes recognise non-self antigens.

A

antibody / immunoglobulin/ IgG, on cell surface/on cell membrane ;
(act as) receptors ;
ref. to antigen-binding/AW ;
(shape) specific / complementary, to antigen ;

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49
Q

Outline how plasma cells produce antibody molecules.

A

DNA/ gene transcribed/ mRNA using DNA as template/AW ;
A transcription unqualified
idea of mRNA associating with ribosome(s) ;
ref. to tRNA with specific amino acid (carried to ribosome) ;
pairing/AW of codons on mRNA with anticodons on tRNA ;
formation of peptide bonds (between adjacent amino acids) ;
antibody /protein/ polypeptide(s), enters RER/ moves to Golgi body ;
ref. to forming, secondary / tertiary structure ;
antibody /protein/ polypeptide(s), modified/processed/glycosylated/ formation
of quaternary structure/ formation of disulphide bond(s) in Golgi (body / apparatus /
complex) ; I ref. to packaging

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50
Q

Describe how antibody molecules are released from the plasma cell.

A

vesicles move to cell/ surface/plasma, membrane (via cytoskeleton) ;
R secreting vesicles unqualified
vesicles fuse with cell (surface) membrane/exocytosis ; R active transport
movement of vesicle/ exocytosis requires energy or ATP/ is active ;

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51
Q

Explain the role of meomory cells

A

) memory cells ; A form immunological memory I ‘gives immunity’
remain/ stay in circulation/ blood/lymphatic system ;
R ‘last a long time/ long lived’ unqualified
for secondary response ;
fast(er) response when exposed again to same pathogen/ same antigen ;
A fast(er) clonal selection/ fast(er) clonal expansion
A divide quickly /rapidly
A long(er) lasting response
to form plasma cells (and more memory cells) ;
more antibodies produced/higher concentration of antibodies ;
R if in context of memory cells
to prevent person feeling ill/ to prevent symptoms ;

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52
Q

Acute lymphoblastic leukaemia (ALL) is a cancer of B-lymphocytes. It is very rare in adults,
but more common in children. A study in 2009 found that exposure to tobacco smoke in the
home may put children at risk of developing ALL.
Suggest how smoking by adults in the home may put their children at risk of cancers, such as
ALL

A

breathing in/ inhale smoke/ ‘second hand’ smoke/ sidestream smoke ;
A passive smoking
I exposed to smoke
2 (tobacco smoke contains) carcinogen(s) ;
3 causes mutation/ described ;
e.g. change to/alters / damages, DNA R if in wrong type of cell
4 leads to uncontrolled cell division/ mitosis / growth ;
5 forming a tumour/ mass of cells ;
6 correct ref. to (proto-)oncogenes /tumour suppressor genes ;
e.g. formation of oncogenes / mutation of tumour suppressor genes / ‘switching off’
tumour suppressing genes
mutation of correct named gene = 2 marks
e.g. mutation of tumour suppressor gene

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53
Q

Explain the role of nitrogen fixation in the nitrogen cycle.

A

1 either
converts, (inorganic) nitrogen/ dinitrogen/N2, into organic nitrogen/
ammonia/NH3 / ammonium/NH4
+ ; R if nitrate given
or
lightning converts, nitrogen/ ammonia/NH3 / ammonium/NH4
+
, into,
nitrite/ nitrate (ions) ;
2 reduces nitrogen/ breaks triple bond ;
3 makes (fixed) nitrogen available to, legumes / other organisms /
community / AW ; A ref. to amino acids / proteins
not to be awarded if it follows nitrification
4 increase soil fertility ;
5 balances the loss of fixed nitrogen in, denitrification/ ocean deposits ; [

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54
Q

Farmers in some parts of the world grow legume crops together with cereal crops in the
same field. This is known as intercropping.
Explain how intercropping results in an increase in the yield of the cereals when the
legumes die.

A

idea of decay /decomposition ;
e.g. breakdown by, (saprophytic) bacteria/ fungi
2 legumes eaten by, detritivores ; A named detritivores
3 decomposers produce proteases ;
4 to, hydrolyse/ convert/ change/AW, protein to amino acids ;
5 amino acids are deaminated ;
6 (amino acids) to, ammonia/NH3 / ammonium (ions)/NH4
+ ;
7 nitrifying bacteria/Nitrosomonas, convert ammonia to nitrite (ions);
8 nitrifying bacteria/Nitrobacter, convert nitrite to nitrate (ions) ;
if mp7 or mp8 not awarded allow one mark for the following as mp9
9 (named) nitrifying bacteria convert, ammonia/ ammonium, to nitrate
(ions) ;
mp10 only to be awarded following nitrification
10 nitrate (ions) used for making, amino acids / proteins (hence increase in
growth of cereals) ;

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55
Q

explain how the response to a second infection by this bacterial
pathogen differs from the first.

A

faster ;
in context of whole secondary response
2 memory cells;
in context of production during the first response
3 idea that there are many more cells specific for this pathogen ;
4 (so) increases chances of encountering pathogens more quickly /AW ;
5 fast(er) production of, B lymphocytes / plasma cells / antibodies /helper (T)
cells / cytotoxic T cells / cytokines ;
6 greater concentration of antibodies (in, blood/ lymph) or greater numbers of, B/ plasma, cells ;
A more, antibodies / plasma cells /B cells
7 pathogen, removed/ killed, faster ;
8 person does not become ill/ no symptoms ;
A pathogen does not, spread through the body / infect cells /AW

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56
Q

Suggest how each of the following reduces the effectiveness of an immune response.
(i) The number of T-lymphocytes is reduced in a person with HIV/AIDS.

A

little/ no/ slower/weak, immune response ;
stated function of T-lymphocytes, does not occur/ occurs slowly ;
e.g. release of cytokines / stimulating macrophages / stimulating B cells /
killing infected cells
high susceptibility to infectious diseases ;

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57
Q

Suggest how each of the following reduces the effectiveness of an immune response
Some pathogens are covered in cell surface membranes from their host

A

pathogen not recognised, as non-self/ foreign ;

pathogen is recognised as self ; A non-foreign

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58
Q

Suggest how each of the following reduces the effectiveness of an immune response
B-lymphocytes do not mature properly and do not recognise any antigens

A

no, antibodies /plasma cells / memory (B) cells, produced ;
no humoral response ;
no antigen presentation by B cells ;

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59
Q

name of TB pathogen
type of
organism

A

Mycobacterium
tuberculosis

bacterium

via, (airborne)
droplets / aerosol(s)
(infection) ;

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60
Q
name of malaria pathogen
type of
organism 
mode of
transmission
A

Plasmodium ;

protoctist

(feeding or biting by)
Anopheles / mosquito ;

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61
Q

what are the different modes of transmission of HIV

A

sexual intercourse/ passed via semen/ passed via vaginal fluids /AW ;
blood transmission ; A described, e.g. blood transfusion
sharing (contaminated), needles / syringes
accept transmitted in body fluids for one mark if above two points not gained
mother to, foetus / baby, transmission ;
A described, e.g. across placenta/ during birth/ breastfeeding

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62
Q

Explain why antibiotics do not affect viruses.

A

b) antibiotics (only) used against bacteria (and some fungi) ;
idea that antibiotics act at a cell structure not possessed by virus ;
e.g. viruses, do not have, a cell wall/ a cell surface membrane/ribosomes
suggestion that viruses are, inside host cells / not within reach ;
antibiotics act only on, living/ growing, cells (viruses do not grow) ;
antibiotics do not act on, protein coat/ capsid/ capsomeres / viral envelope ;

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63
Q

suggest the role of viral polymerase

A

replication of RNA/ to make copies of genes /AW ;
transcription/ production of mRNA ;
detail ; e.g. to make viral proteins ;

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64
Q

outline how monnoclonal antibodies are made

A

immunise/ inject/AW, mice / small mammals, with /antigen ;
immune response occurs / leave for a number of weeks ; A description
harvest/ collect/AW, splenocytes /B-lymphocytes /B-cells / plasma cells ;
fuse with, myeloma cells / cancer cells ; A tumour
form hybridoma cells ;
select for (hybridoma) cells secreting antibody against, /antigen ;

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65
Q

An activated B-lymphocyte divides repeatedly by mitosis to produce many identical
plasma cells.
(i) Explain why it is important that many identical plasma cells are produced.

A

part of the immune response ; A primary / secondary, response
many plasma cells
2 to produce high, concentration / level / AW, of, antibody / immunoglobulin ;
3 (high concentration antibody so) more effective against pathogens / AW ;

identical plasma cells
4 specific / particular / AW, to an, antigen / epitope ;
in context of antibodies or plasma cells
5 antibody (molecules) produced are all the same ; A ora, qualified
6 only the gene coding for particular antibody, switched on /
transcribed / expressed ;

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66
Q

Explain why tuberculosis (TB) is known as an infectious disease.

A

caused by, a pathogen ;
2 transmissible / communicable ; A passed from, person / animal, to person
ignore contagious
in context of tuberculosis
3 (pathogen is) a bacterium / Mycobacterium (tuberculosis / bovis) / M. tuberculosis /
M. bovis ;
4 mode of transmission detail ; one from
aerosol / droplet, infection / transmission
in droplets, from (infected) person, exhaling / AW
/ coughing / sneezing / talking in droplets, / inhaled /
AW, by (uninfected) person
person, drinks (unpasteurized) milk / eats meat, from infected cattle

A contaminated, milk / meat

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67
Q

Outline the role of antibiotics in the treatment of infectious diseases, such as TB

A

kill bacteria / bactericidal ; A cause bacteria to, lyse / burst A destroy
2 (or) bacteriostatic / prevents bacterial growth / prevents bacterial replication;
A ref. to preventing protein synthesis / inhibiting metabolic reactions
3 ref. to preventing spread (of bacteria) within body ; A prevents reservoir for re-infection
4 do not affect, human cells / human tissue / not toxic (to humans) ;
5 prevents death / consequences may be fatal if no antibiotic treatment / AW ;
A ref. to, alleviating symptoms / faster recovery
A restores good health / person feels well again / person cured
6 ref. to role in preventing, transmission / spread, of disease ; do not confuse with mp 3

ref. to (antibiotic) treatment of TB ; e.g.
one of isoniazid, rifampicin (rifampin), pyrazinamide, ethambutol, streptomycin
one of 6–12 months (latent), longer for active disease, two years or more for
drug-resistant forms
need combination treatment if active disease
ref. to, MDR-TB / multidrug- resistant TB or XDR-TB / extensively drug-resistant TB
8 part of DOTS regimen / described ;
(directly observed therapy short-course / direct observation treatment short course)
[max 4]

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68
Q

) Suggest what epidemiological evidence would lead to the conclusion that tobacco
smoking is a risk factor for TB.

A

statistical, correlation / link / association, between smoking and TB ; AW
A another valid suggestion in addition to mps 2-6 suggesting link
2 where TB, cases / death rates, are high tobacco smoking is also high ;
3 in areas where there is, no overcrowding / AW, smokers have higher number of TB
cases ;
4 (ref. projects) death rates from TB reduced where patients stop smoking ;
5 higher cases TB in work places where smoking occurs ;
6 higher cases of TB in children living with parents who smoke

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69
Q

Suggest and explain how the effects of smoking can increase the risk of becoming
infected with TB

A

.1 lack of / paralysed / AW, cilia, so mucus, not wafted away / accumulates ;

R dead cilia
2 pathogen / bacteria / Mycobacterium, remains in lungs / accumulates ;
3 ref. to increased opportunity / AW, for bacteria to, enter cells / infect ;
4 nutrients provided by excess mucus encourage growth ; AW
5 smoking weakens the immune system ;
6 detail ; e.g. fewer / less active / AW, phagocytes / macrophages

70
Q

List two treatments used by medical practitioners to treat coronary heart disease.

A
coronary bypass (surgery) / coronary artery bypass (graft) ;
 A bypass, surgery / graft / operation
 R heart bypass
 heart transplant ;
 angioplasty ;
 stent (insertion / AW) ;
71
Q

Define the term gene mutation.

A

change / alteration / AW, in sequence / order / arrangement, of, bases /nucleotides (of DNA /
gene) ; change to give a new allele ;
one additional detail ;
(may result in) altered, changed / non-functioning / no, polypeptide / protein
ref. to changed genetic code / different codons
different sequence of amino acids / different primary structure
named type of mutation
example e.g. HbS

72
Q

Explain why existing vaccines may no longer be effective when the surface antigens
of a disease-causing organism change.

A

ref. specificity ; in context of the immune response
qualified ; e.g. existing , (B / T) lymphocytes / B-cells / T-cells, no longer
activated / no recognition ora
R if T lymphocytes produce antibodies
existing plasma cells do not produce new antibody ora
existing memory cells no longer activated / AW ora
different / new, immune response required ora

73
Q

State precisely the type of immunity gained by a person who has been vaccinated.

A

artificial active

74
Q

Outline two reasons why measles is still common in many parts of the world, even
though the vaccine is available.

A

ref. malnourishment / poor diet, vaccine ineffective / poor immune response / insufficient
protein for antibody production ;
2 some (healthy) people do not respond to vaccines ;
3 one-dose not always effective / problems administering boosters ; AW
4 ref. percentage cover / herd immunity, insufficient ; A description
A idea of people in rural areas have less / no, access to vaccine
A people avoid vaccine, worry about side-effects / other reason
5 ref. cost to authorities ; e.g. of, administering vaccination programme
6 people in some areas cannot afford to buy vaccine
7 vaccine may not be thermostable ; AW
8 high density of population / overcrowding, increases chance of spread ;

75
Q

three ways food web turns to organic matter in the soil

A

excretion
egestion ;
death
idea of shed body parts ; e.g. leaf fall/ shed petals / fruit drop/ moulting

76
Q

People with sickle cell anaemia have a form of haemoglobin that is unable to bind to oxygen
efficiently. The cause of the condition is a mutation in the gene coding for the β-globin
polypeptide of haemoglobin.
Outline how this mutation can lead to an altered amino acid sequence of the β-globin
polypeptide

A

nucleotide/ base, sequence of, DNA/ gene, changed/AW ;
A new allele (formed)
2 base substitution (mutation)/(DNA) thymine replaced by adenine/(DNA is)
CTC to CAC/CTT to CAT (template codon) ;
this cannot be used for mp 1 as well
3 altered/ changed, mRNA codon ; (allow codons) A idea of different mRNA
R altered genetic code
4 (mRNA codon is) GAG to GUG/GAA to GUA ;
5 glutamic acid, substituted/replaced/AW, by valine ; A glutamate
A glu and val
6 tRNA/ anticodon, with different amino acid (to ribosome) ;
A tRNA with different anticodon
7 AVP ;
e.g.amino acid substitution at position 6
valine, hydrophobic /AW (R-group)
glutamic acid, polar/AW (R-group)

77
Q

Discuss the factors that should be considered when making recommendations concerning
the prevention of sexual transmission of HIV. and solutions

A

(geographical) availability of condoms so condoms should be available (in all
relevant locations) ;
where available, insufficient stock of condoms condoms should be stocked in sufficient
quantities ;
condoms (available but) unaffordable free/affordable, condoms (should be
provided) ;
A condoms should be provided;
low level/ no, advertising campaigns for
condom use
ref. advertising campaigns for, condom
use/ safe sex /protective
sex ;
poor condom storage (idea of deterioration) safe storage of condom supplies (to avoid
deterioration) ;
lack of education in, use of condoms / how HIV
is spread/other relevant
R low level of awareness of HIV/ lack of
education about HIV
ref. education ; e.g. should use
condoms / proper use of condoms
A (should practice) safe sex / protective
sex ;
low level of (interest in) condom use or,
religious / cultural, objections
A few people use condoms
ref. changing perception of people to
encourage use (of condoms) ;
identifiable, high risk / named high risk, groups
e.g. sex workers, (male) homosexuals, multiple
partners,
IV drug abusers (in context of sexual activity)
idea of targeting, high risk / named high risk,
groups ;
e.g. sex workers, homosexual males,
multiple partners, IV drug abusers
IV drug abusers (in context of sexual
activity)
low rate of male circumcision encourage circumcision procedure/ train
health personnel ;
poor treatment of sexually transmitted infections treatment of sexually transmitted infections
(as risk of contracting HIV increases) ;
no/ poor/AW, antiretroviral therapy ref. antiretroviral therapy reducing risk of
sexual transmission ;

78
Q

role of t hlper cells

A
release/AW, cytokine/ lymphokine/
interleukin ; stimulate/AW, humoral/B-lymphocyte/ B-cell, response ;
humoral/B-lymphocyte/B-cell, response not stimulated ;
(stimulate B-cell response so) antibodies
produced ;
A secreted/released
R if antibodies from T-cells
stimulate/AW,
A (result in) angry macrophages
A make macrophages more active (in
phagocytosis)
remain in circulation for second
encounter with antigen ; AW
79
Q

Suggest how whooping cough is transmitted

A

1 aerosol/ droplet, infection ;
only need to have one of ‘infected’/ ‘uninfected’ to gain mps 2 and 3
2 infected/AW, person, coughs / breathes / spits / talks / sneezes ;
3 uninfected/AW, person, inhales / inspires / breathes in, droplets ;
2/ 3 allow one mark if mps 2 and 3 given with no reference to, infected/ uninfected
4 organism/ pathogen/bacteria/B. pertussis, in, airborne droplets / droplets in air ;
A without ‘airborne’ or ‘in air’ if mp 2 gained

80
Q

Suggest how phagocytes can recognise the difference between healthy body cells and
cancerous tumour cells.

A

healthy body cells, (recognised as) self/ have self-antigens ; A non-foreign
2 cancer(ous)/ tumour, cells, (recognised as) non-self/ have non-self antigens ;
A foreign
3 idea that changes occur to structure of cell surface membrane of, cancer(ous)/
tumour, cells ;
4 phagocytes have receptors for, non-self/ foreign, antigens or
phagocytes have receptors for antibody complexed to non-self/ foreign antigens ;

81
Q

Only a small proportion of the light energy striking the leaves of producers becomes
converted to chemical energy. The proportion that is converted is known as the photosynthetic
efficiency (PE).

(i) Outline the possible reasons why a large proportion of light energy striking the leaves of
plants is not converted into chemical energy.

A

energy losses from
1 reflection (from leaf surface) ;
2 idea that some light, passes through (leaf)/ misses chloroplasts / strikes
non-photosynthetic tissue ;
A suggestion that cell walls may not allow all of light through
3 heating plant ; I lost as heat to surroundings A converted to heat
4 evaporation ; A transpiration
5 not all light (reaching chlorophyll) is, the right wavelength (for photosynthesis)/AW/
absorbed by chlorophyll ;
A idea that only a proportion of light energy is useable
A absorbed and, lost as phosphorescence/ lost as luminescence/re-emitted
6 ref. to photosynthetic process inefficient ; A loss of heat energy during
photosynthesis
7,8 AVP ;; e.g. ref. to photorespiration
ref. to factors that limit photosynthesis

82
Q

Only a small proportion of the light energy striking the leaves of producers becomes
converted to chemical energy. The proportion that is converted is known as the photosynthetic
efficiency (PE).
Suggest the advantages of growing crops with high PE for food production or for biofuel.

A

increased production of / more, biomass / plant matter / named (e.g. carbohydrate /
cellulose / starch / oils) ; R more plants I more crop I food
2 (so) more energy / more energy stores ;
A more chemical energy produced
A higher energy
A suggestion that high PE crop may be more energy dense
3 more crop / greater yield, per unit, area / volume / time ; A each year
4 idea of (comparatively) less space required (for growing) ;
5 ref. to supplying increasing demand for, food / fuel ;
6 more, profit (for farmers) / economic / AW ; I cheaper
7 AVP ; e.g. efficient use of carbon dioxide

83
Q
Name two organic compounds containing nitrogen that are made by plants and state one
function of each in plant growth.
A

mino acids production of proteins (for cell growth);
A provide energy / for respiration
proteins cell division/ mitosis / increase in cell number/
increase in, biomass or yield/(cell) membranes ;
A reproduction A cell cycle
A (tissue) repair
A provide energy / for respiration
enzymes synthesis of, macromolecules or organic molecules /
anabolic reactions / for photosynthesis / for
respiration ; [max 2]
A named molecules e.g. carbohydrates / amino
acids / proteins / lipids / nucleic acids
(organic / nitrogenous) bases component/ synthesis of, nucleotides
component of, DNA/RNA/ nucleic acids ;
nucleotides component/ synthesis of, DNA/RNA ;
DNA ref. genes /genetic material/ coded information/
genetic information, (for protein synthesis) ;
RNA ref. transcription/ translation/ protein synthesis ;
(some) phospholipids (for cell) membranes ; R lipids
ATP synthesis / anabolic reactions /active transport/
translocation/ described ;
A provide energy for reactions
chlorophyll photosynthesis / light (dependent) stage ;
NADP (in) photosynthesis / light (dependent) stage ;
NAD (involved in) respiration ;
FAD (involved in) respiration ;
auxin growth hormone/ cell elongation/ cell division ;
cytokinin growth hormone/root growth ;

84
Q

Planning the prevention and control of a disease using a vaccination programme means that
financial costs must be considered.
State two examples of these costs.

A

1 preparing/ manufacturing/ purchasing, vaccine ; A cost to provide vaccine
free to developing countries
2 disposables / equipment to administer (vaccine) ;
e.g. syringes / needles /(protective) gloves
3 storage ; e.g. space, security
4 refrigeration/ maintaining cold chain ;
5 transport (of, vaccine/ health care workers) ;
6 wages / training, of staff involved ; e.g. wages for, health care workers
administering vaccine/ staff involved in training health care workers
7 record keeping/ contact tracing ;
8 advertising/ informing/ marketing/education ;
9 research/ development ;
10 setting up vaccination/ immunisation, camps (for remote/ epidemic, areas) ;
I building, hospitals / clinics

85
Q

Explain what is meant by a gene.

A

treat as neutral unit of inheritance
sequenceof, nucleotides /bases ;
section/ length/ part, of DNA (molecule) ;
codes for a polypeptide ; A protein for polypeptide A enzyme
A information to produce a polypeptide
A codes / information, for sequence of amino acids / primary structure (of
a, polypeptide/ protein)
R genetic code for a polypeptide

86
Q

Outline how a gene mutation can lead to the formation of an altered polypeptide
where one amino acid is replaced by a different amino acid.

A

(in DNA/ gene) altered, sequence/AW, of, nucleotides / bases ;
I DNA sequence
2 base substitution
or base/ nucleotide, replaces another, base/ nucleotide;
A example must be in context of, DNA/ gene
3 (mRNA synthesised) during transcription ;
4 (mutation leads to) altered/AW, mRNA/ messenger RNA ;
5 (only) one (mRNA) codon changed/ a different codon ;
A one DNA, triplet/ codon, changed I ref. to codons changed
6 tRNA, with / has, a different anticodon ;
7 (tRNA) brings, a different/ a changed/ the incorrect, amino acid, during
translation/ to the ribosome ;
8 codon-anticodon, binding/ complementary /AW ; A matches
R amino acid with anticodon

87
Q

Explain how natural disasters can sometimes result in transmission of communicabl diseases to more
individuals.

A

general ref. to problems associated with increased numbers of people and lack of
infrastructure ;
examples ;;
e.g. problem providing, safe / uncontaminated, drinking water ;
faeces / sewage, mixing with drinking water ; A no / poor, sanitation
unable to practise good hygiene ; A example e.g. hands not washed after defaecation
infected people sharing latrines with uninfected / AW ;
lack of, medical care / treatment, leading to larger pool of infected people (at any one
time)
lack of, health services / drugs / antibiotics / ORT / skilled personnel
unable to supply sufficient vaccines
lack of food / poor diet, so vaccines less effective
credit relevant examples linked to a particular type of disaster

88
Q

Explain why the Plasmodium parasites were killed using radioactivity and not by using high
temperatures.

A

ref. vaccines contain antigens ;
2 antigens are (mostly), proteins / glycoproteins ;
3 antigens, denatured by heat / not denatured by radioactivity ; A proteins denatured in
context of antigenic proteins
R parasite is denatured
4 detail e.g. loss of tertiary structure / bonds break ;
5 shape to be maintained for specificity of immune response / AW ;
6 AVP ; e.g. ref. to production of memory cells (for immunity)

89
Q

explain why the researchers decided to use the form of the

parasite which is injected by mosquitoes and not the form which leaves the liver.

A

1 first form of, pathogen / parasite, free / exposed, in plasma ;
A not inside cells
2 second form of, pathogen / parasite, concealed / hidden, in liver / red blood cells ;
for either mp 2 or 3
3 ref. to degree of exposure to antibodies / lymphocytes
idea that
4 fewest number of parasites to destroy / earlier defence always more effective ;
5 vaccination against form leaving liver would, not protect against liver invasion / still cause
liver damage ;
6 AVP ; e.g. suggestion that first form of parasite is easier to harvest

90
Q

Outline the events that occur following injection of the parasites, which lead to the
production of antibodies

A

1 primary (immune) response / artificial active response ;
2 antigen presentation / described ;
3 clonal selection / described ; e.g. A specificity to malarial antigen
4 clonal proliferation / B-lymphocyte division by mitosis / AW ; A B cell
5 detail of changes occurring from B-lymphocyte to plasma cell ;
6 B-lymphocytes / B cells / plasma cells, produce antibody ;
7 correct ref to role of Th cells in context ;

91
Q

commmunity

A

all populations of all species within a specified area / AW, at a particular time ;

92
Q

describe the features of producers.

A

photosynthetic / carry out, photosynthesis / carbon fixation ; A autotrophic
2 conversion of light energy to chemical energy ;
3 equation ;
4 have light-absorbing pigments ; A chlorophyll
5 ref. to independence or dependence of other organisms ; in context of energy
6 ref. to input of energy to ecosystem ;
7 base of the food chain(s) / first trophic level / AW ; A consumed by, herbivores /
primary consumers

93
Q

In the wild, only about 10% of the energy taken in by the catfish in their food is used
to increase biomass.
Suggest why this percentage is lower in the wild than in the pond

A

more confined space so less movement ;
move more so greater energy loss (through respiration / as heat ) ;
more predators so use more energy escaping from them ;

94
Q

Dead animal and plant material can also contribute to the pool of inorganic nitrogen
in soil.
Describe how this happens.

A

decomposition/decay ;
A reference to decomposers
saprotrophs / bacteria/ fungi ;
A detritivores
digest/ breakdown/ hydrolyse, organic nitrogen/ protein/ amino acids / urea ;
protease/urease ;
deamination ;
production of ammonium (ions)/ ammonification ;
nitrification/ammonium (ions) to nitrate (ions) ;

95
Q

Nitrogen and phosphate are both cycled more rapidly in ecosystems where there
are high rates of growth within trophic levels and high rates of energy flow between
trophic levels.
With reference to the use of both nitrogen and phosphate in organisms, explain
this statement.

A

growth linked to, increase in cell size/ cell number ;
2 growth linked to, increase in biomass /reproduction ;
3 increases energy available as food for next trophic level ;
4 nitrogen is in, amino acids / proteins, for growth ;
5 ATP (containing phosphate) required for, transcription/protein synthesis / enzyme
synthesis / anabolic reactions /growth ;
6 idea that, growth of cells / cell division, requires membrane synthesis ;
7 nitrogen in membrane proteins / phosphate in membrane phospholipids ;
8 (cell division and), DNA, synthesis /replication ;
9 idea that more biomass (per unit time) returned to soil ;
10 AVP ; e.g. ref. to phosphate taken up by plants and passed into food chain

96
Q

Define the terms:

(i) vaccination

A

1 (method to) stimulate/AW, an immune response ;
A gives immunological memory
2 giving/AW, antigens ;
3 (method to provide long-term) artificial active immunity ;
4 one relevant detail ;
e.g. no ability to cause disease
ref. to, harmless /AW, form of pathogen used
(protection through) production of (specific) memory cells
(contains, pathogen/antigen) in an injection or an oral dose

A (to provide long-term) artificial active immunity
if not already credited in mp 3

97
Q

communicabe disease.

A

(disease) caused by, a pathogen/ microorganism ;
A two of bacteria, virus, fungus, protoctist
one relevant detail e.g.
transmissable/ communicable/ passed from one organism to another/AW ;
A spread to others if qualified
affecting the normal function of the body / causing ill health ;

98
Q

Suggest why TB is more likely to be fatal in people who have HIV/AIDS than in those who do
not have HIV/AIDS.

A

(HIV/AIDS leads to) weak immune system/reduced immunity (to disease) ;
detail ; e.g. reduced action of phagocytes
Th lymphocytes low in number
B-lymphocyte response low
(so TB) pathogens, can multiply faster/ are not destroyed before they cause
disease ;
idea that important, organs / systems, may already be suffering from
consequences of HIV/AIDS (so more likely to stop functioning) ;
ref. to, inactive/dormant/ latent, TB more likely to become active ;

99
Q

Suggest advantages of Rhizobium living in root nodules of leguminous plants.

A

idea that Rhizobium will receive, photosynthates /assimilates (from plant) ;
gains, carbohydrate/ amino acids ;
for energy / growth/replication ;
receives oxygen ;
idea of (nodules provide) correct living conditions /ideal habitat/ anaerobic
conditions (for nitrogenase)/AW ;
A ref. to protection, qualified mutualistic relationship ; A described

100
Q

Explain the role of Rhizobium in the growth of leguminous plants.

A

involed in nitrogen fixing and the production of, ammonium/NH4
+ / ammonia/NH3 ;
(fixed/ useable) nitrogen transferred to plant ;
used for amino acid production (in plants) ;
ref. to other uses relevant to growth ; e.g. in DNA replication/transcription
increased/used in, protein synthesis ; A named protein
(for) production of new, cells / tissues ;

101
Q

Some transcription factors may prevent transcription.

Suggest two ways in which they may do this.

A

may prevent
breaking of hydrogen bonds between, base pairs / bases /nucleotides,
(and access of RNA polymerase) ;
attachment of, RNA polymerase (to DNA) ;
progress / functioning, of RNA polymerase (along gene) ;
synthesis / elongation of (pre) mRNA ;
AVP ; e.g. interfere with action of helicase

102
Q

Suggest why plasma cells contain a large quantity of rough endoplasmic reticulum.

A

(endoplasmic reticulum/RER) has ribosomes ;
(ribosomes /RER) site of protein synthesis ;
antibodies are proteins ;
RER for, modification/transport/ transport vesicle formation ;

103
Q

(e) State two reasons why the vaccination programme was successful in eradicating smallpox

A

two relevant e.g.
1 vaccine, thermostable/ freeze-dried ; A idea of longer shelf-life/ no wastage
2 virus did not mutate ; A pathogen/ strain
3 same vaccine could be used everywhere ;
4 cheap to produce (in large quantities) ;
5 ease of production ;
6 used a live virus / vaccine gave a strong immune response ;
7 no need for boosters ;
8 ease of administration ; e.g. ref. to enthusiastic volunteers
needles could be, sterilised/re-used
9 high percentage cover/AW ;
10 ref. to ring vaccination/ described ;
11 global effort/AW

104
Q

Explain how a single dose of vaccine can provide immunity for up to 10 years when the
plasma cells are short-lived.

A

memory cells produced (along with plasma cells) ;
to max 2
idea of greater number of (specific immune system) cells ;
(memory cells are) long(er) lived/remain in circulation ;
memory T and B cells ;
ref. to/ detail of, faster secondary response (to give immunity) ;

105
Q

Describe how nitrogen in nitrate can be returned to the atmosphere in the form of nitrogen
gas.

A

by bacteria ;
denitrification/reduction;
ref. anaerobic conditions ; A ref. to waterlogging

106
Q

) ecosystem

A
idea of (unit made up of ) biotic and abiotic, components ; AW
 further detail ; interacting/ functioning together ;
 A idea of self-sustaining unit
107
Q

Explain what is meant by the term non-self antigens.

A

non-self
foreign / AW ; A not from the person’s own body
triggers / AW, an immune response/production of antibodies ;
A other events in immune response described
antigen
protein/ glycoprotein ; A polysaccharide
ref.to, binding of specific antibody /formation of antigen-antibody complex ;

108
Q

During the first few years after the introduction of streptomycin treatment, an increasing
number of M. tuberculosis bacteria developed resistance to streptomycin.
Outline how this happened.

A

incomplete treatment/ dose not finished ;
2 not all bacteria killed/ some bacteria survive ; R TB for bacteria
3 mutation ; R mutation to give immunity
4 further detail of mutation ;
5 selection of resistant bacteria/resistant bacteria selected for ;
6 resistant bacteria reproduce/ vertical resistance ;
7 death of, susceptible/ non-resistant, bacteria ;
8 AVP ; e.g. horizontal resistance/described

109
Q

describe the modes of action of the two cells in defence against infectious diseases.
phagocyte

A

phagocyte move to sites of infection ; ingest / engulf / pseudopodia enveloping / phagocytosis of / endocytosis of, bacteria / microbes / pathogens / AW ; R antigens, virus (form) phagocytic / endocytotic, vacuoles ; A vesicles, phagosomes ref to lysosomes ; enzymes / named (hydrolytic) enzymes ; digest / hydrolyse, (bacteria / AW) ; antigen presentation / description ;

110
Q

describe the modes of action of the two cells in defence against infectious diseases.
plasma cell

A

produce / secrete / release / synthesise , antibodies ; A make into, plasma / tissue fluid / lymph ; A blood antibodies are proteins ; ref to, RER / ribosomes ; specificity qualified e.g. of, antibodies / lymphocyte / plasma cell or description e.g. each type of plasma cell produces one type of antibody ; Golgi (body) packages antibodies / ref to formation of (Golgi) vesicles ;

111
Q

Explain why the antibiotics used to treat TB are taken in combination over a long period of time.

A

(bacteria likely to be) resistant to (at least) one antibiotic (so useless) ; less likely to be resistant to all / chance that bacteria will develop resistance to all antibiotics used is very small ; ref to mutation / change to DNA ; (bacteria are) inside cells where protected from antibiotics ; (mycobacteria) divide / grow, slowly ; ensures all bacteria killed / reduces below critical level ; otherwise, bacteria remain / reservoir of infection ; (so) prevents development of antibiotic resistance ;

112
Q

Describe the roles of T-lymphocytes in a primary immune response

A

helper cells secrete / release / produce, cytokines / lymphokines / hormones ; to stimulate B cells to, divide / develop into plasma cells ; (which) produce antibodies ; stimulate macrophages to carry out phagocytosis ;

cytotoxic / killer T cells seek out / find / bind to, (foreign) antigens, on host cells / pathogens ; destroy, virally infected host cells / intracellular parasites / viruses ; attach to surface of cells / ‘punch holes’ into cells / disrupt cell surface (plasma) membrane; (release) toxic substances / hydrogen peroxide (into cells) / interferons ;

113
Q

Describe three functions of cell surface membranes,

A

control of entry and exit of substances ; barrier to, polar molecules / water soluble molecules ; adhesion ; idea of retaining, large molecules / cell contents; allow substances across, passively / by diffusion ; ref to channel proteins ; A pore allow transport protein once move substances through carrier proteins ; active transport ; ref to facilitated diffusion ; endocytosis / exocytosis / phagocytosis / pinocytosis ; recognise, hormones / neurotransmitters / chemical signals ; sites of chemical reactions / sites for enzymes ; the recognition of antigens

114
Q

Explain why malaria is restricted to the tropics

A

transmitted by, Anopheles / mosquito / (insect) vector ; P. falciparum / parasite, needs, warm / hot, temperatures / >20oC, to complete its life cycle (in the mosquito) ; requirement for areas of still water (ref. mosquito life cycle); eradicated in areas outside tropics (e.g. North America)

115
Q

Describe how antibodies provide protection against pathogens

A

secreted / synthesised / produced / released, by, plasma cells / B lymphocytes / B cells ; 2 combines / AW, with, antigens / pathogens / toxins / viruses / bacteria / microbes ; A ‘bonds with’ / ‘sticks to’ / ‘attaches to’ R ‘disease’ 3 ref to, specificity / described ; in context of antibody / B cells / antigen 4 variable region is antigen binding region ; R ‘receptors on antibodies’ 5 neutralises toxins / antitoxin(s) ; 6 lysis of pathogens / described / lysin(s) ; R breaks down 7 prevents viruses entering cells ; 8 clumps / agglutinates / aggregates / AW, bacteria ; R ‘coagulation’ 9 opsonisation / opsonins ; A enable recognition 10 coats / AW, bacteria to facilitate phagocytosis ; only in context 8 or 9 11 receptors on phagocytes for constant regions (of antibodies)

116
Q

Discuss the problems in attempting to control the spread of HIV/AIDS

A

1 no (effective) vaccine ; 2 HIV has a high mutation rate ; 3 antigens change / different antigens / different strains ; 4 no cure ; 5 drugs, are expensive / not widely available / not effective / AW ; 6 vertical transmission / mother to child ; problems with: 7 symptomless carriers (spreading the virus) ; 8 testing people for HIV status ; 9 providing, condoms / femidoms ; 10 promiscuity ; 11 educating about risks / AW ; 12 reuse of needles ; 13 tracing contacts (of infected people) ; 14 testing / screening, blood donations ; 15 treating, blood / blood products, to, destroy / inactive / ‘kill’, HIV ; 16 ref to cultural issues ; accept relevant examples 17 ref to poverty ; 18 AVP ; e.g. war / civil disturbance, out of date drugs, ref to transport links ignore resistance of HIV

117
Q

Explain why the energy efficiency between secondary and tertiary consumers is greater than that between producers and primary consumers

A

1 some parts inedible ; 2 indigestible / cannot digest cellulose or lignin ; 3 more material goes to decomposers (rather than consumers) ; 4 plant material is less energy rich / animal flesh is more energy rich ; 5 manipulated data in support ; e.g. ×2 to decomposers from producers 0.8% (energy available to primary consumers divided by the energy available to plants)

118
Q

Describe the roles of decomposers in recycling nitrogen

A

protein → ammonia / ammonium ions = 1 mark 1 convert protein → amino acids ; 2 deamination ; 3 urea / amino acids → ammonia / ammonium ions ; A ammonification 4 make, ammonia / ammonium ions, available to nitrifying bacteria ; A role of nitrifying bacteria / correctly named

119
Q

Very little of the energy consumed by grazing animals is available to carnivores.
State two reasons why this is so

A

loss (of energy-containing food in producers or in grazers) in
indigestible parts / not being absorbed / faeces / egestion ;;
one mark for producer, one mark for grazer

excretion (in, grazers / herbivores / primary consumers) ;
respiration (in, grazers / herbivores / primary consumers) ;
loss of energy in movement / AW (in, grazers / herbivores / primary consumers) ;
AVP ; e.g. heat energy

120
Q

State why lung cancer is categorised as a non-infectious disease

A

not transmissible from one person to another / AW ;

not caused by a pathogen ; R bacterium / virus / fungus / AW / ‘worm’

121
Q

Explain the roles of the cells in an immune response

A

foreign / AW, antigens are non-self ;
non-self / foreign antigens, induce immune response ; AW ora

macrophage / APC (A)
phagocytosis / described ;
cuts up / AW, bacterium / pathogen ;
presents antigens / becomes antigen presenting cell / antigens on cell surface ;

B/T, cells (B and C)
antigen recognition by lymphocytes ;
(with) complementary / specific, receptors / immunoglobulins (B) / antibodies (B) ;
divide by mitosis ; A clonal expansion
ref. formation of memory cells (for secondary response);

Th cells (C)
secrete cytokines to stimulate B cells ;
cytokines stimulate macrophages ;

Tc/k cells (C)
ref. destroy pathogen / AW ;
produce perforin / AW ;

B cells (B)
B cells become plasma cells ;
(plasma cells) secrete antibodies ;

AVP ; e.g.
macrophages, non-specific / faster response
ref. specificity of, lymphocytes / B and T cells
antibody variable region is the antigen binding site

122
Q

Describe how mitosis is involved in an immune response

A

occurs in both primary and secondary (immune) responses ; selected / specific / AW ; lymphocytes / B -cells / T-cells / divide (by mitosis) ; clonal expansion / described in terms of producing, clone / many cells ; A idea that different types of immune cell can result reference mitosis in memory cells (for rapid) secondary response ;

123
Q

how macrophages function to protect the lungs from becoming infected

A

1 recognise, non-self / foreign, antigens, (on pathogen) ;

2 receptors (on macrophage) bind antigens (on pathogen) ;

3 (or), pathogen / AW, adheres / ‘sticks’, to (cell surface) membrane ;

4 infolding of (macrophage cell surface) membrane around / engulf / phagocytosis of, pathogen ; R engulf antigen

5 vacuole / vesicle / phagosome, forms ;

6 ref. to lysosomes ;

7 hydrolytic / digestive / named, enzymes ; e.g. lysozyme / protease / nuclease A pathogen broken down by enzymes

8 hydrolysis of named compound(s) ;

9 ref. to destroying / killing, pathogen ;

10 ref. to antigen presentation ;
accept idea even though does not occur in alveoli

124
Q

what is meant by keystone species

A

changing numbers of keystone species has (large) effect on the rest of the ecosystem ;

125
Q

autotroph

A

carries out photosynthesis/photosynthetic ; A acts as a producer synthesises (complex) organic compounds from inorganic, compounds ; uses light energy ;

126
Q

heterotroph

A

obtains energy from, complex/organic, compounds ; A insects/animals ref. digestion/absorption soluble products ; AW acts as a consumer/feeds on other organisms ;

127
Q

Suggest how a change in the amino acid sequence of the enzyme results in antibiotic resistance.

A

change in, tertiary / quaternary, structure (of enzyme) ; A change in polypeptide, folding / coiling ;

(enzyme) binding site for antibiotic, lost / changes shape ; R active site unless clear that substrate binding and catalytic site remains unchanged

antibiotic / nalidixic acid, cannot bind (so enzyme remains active) ; allow ecf for active site

128
Q

Discuss the consequences of multiple resistance for health authorities

A

risk of, further spread / wider epidemic, (from people still infected) ; AW 2 reduces chance of succesful treatment / higher death rates ; 3 increased, treatment / hospitalisation times ; A takes longer to treat A more complex treatment 4 increased costs of treatment / strain on health budget / AW ;

5 risk of, further resistance / resistance to all antibiotics ; 6 fewer antibiotics left that are effective ; A risk that no antibiotics will be left to successfully treat

7 need to find, new antibiotics / alternative treatment ; A difficulty in finding new treatments / AW 8 (so) cost of research ; allow cost once

9 AVP ; e.g. strain on, resources / health personnel, to treat other diseases need to identify type of resistance so that effective treatment is given education, qualified [4]

129
Q

Suggest how the binding of monoclonal antibody to the diseased cells causes their destruction by cells of the person’s immune system.

A

four from 1 ref. to monoclonal antibody, is recognised as, non-self / foreign ; or diseased cell (now) recognised as non-self / foreign ;

2 stimulates an immune response ;

max three suggestions from 3 recognition and binding by / activation of / AW, T-lymphocytes / B-lymphocytes / AW ; A clonal selection A T- / B-, cell 4 ref. to specificity so healthy cells not destroyed ;

5 clonal expansion / mitosis ;

6 plasma cells (formed that) secrete antibody ; A B-lymphocyte

7 consequence ; e.g. antibody binds monoclonal antibody to lead to cell destruction

8 T-helper lymphocyte secretes cytokine, to activate macrophages / B-lymphocyte response / T-killer response ; AW e.g. stimulates humoral response

9 T-killer / T-cytotoxic, releases, perforin to, punch holes in (cell) membrane / cause death of cell ; AW

10 detail of involvement of phagocytes / macrophages ; e.g. receptor recognition of (monoclonal) antibody engulf the diseased cells with monoclonal antibody attached / AW A diseased cell (with monoclonal antibody) destroyed by phagocytosis [4]

130
Q

Explain the term auto-immune disease.

A

one of failure to distinguish self and non-self (antigens) ; A foreign for non-self immune response / antibodies produced, against self antigens ;

in context of lack of good health R does no harm [1]

131
Q

Apart from a cost benefi t, suggest one advantage of using immobilised phosphatase to produce dephosphorylated DNA.

A

enzyme / phosphatase, can be reused ; enzyme / phosphatase, easily recovered ; enzyme / phosphatase, doesn’t contaminate, DNA / product ; less purifi cation of product / DNA, required ; A less downstream processing required enzyme / phosphatase, longer shelf life / AW ; enzyme / phosphatase, more stable to, temperature / pH

132
Q

State one way of immobilising an enzyme

A

in (sodium) alginate (beads) / encapsulation ; A other named methods, e.g. entrapment / trapped in pores of silica gel adsorption onto, clay / glass / resin (within) polymer / partially permeable membrane, microspheres covalent bonding to support, material / collagen

133
Q

B-lymphocyte activation can occur as a result of direct contact with a specifi c antigen on the invading pathogen.
State two other ways for the B-lymphocyte to become exposed to the antigen.

A

antigen-presenting cell ; A description e.g. macrophage that has phagocytosed pathogen and has antigens on surface vaccine containing antigen ;

134
Q

Suggest why antibodies need to be globular proteins

A

soluble in, blood / plasma / tissue fl uid / lymph ; tertiary / quaternary, structure allows formation of, variable site ; AW idea of easier to transport (than fi brous proteins)

135
Q

With reference to antibody structure, explain what is meant by quaternary protein structure.

A

more than one, polypeptide ; (antibodies have) two heavy and two light, polypeptides / chains ;

136
Q

Name the type of cell used to produce monoclonal antibody.

A

hybridoma (cell)

137
Q

) Phagocytic cells contain many lysosomes.

Describe the function of lysosomes in destroying ingested bacterial cells.

A

lysosomes fuse with, vacuole / vesicle / phagosome ; A form secondary lysosomes lysosomes contain, enzymes / named digestive enzyme ; (catalyse) hydrolysis / digestion ; A breakdown (digests / breaks down) protein / murein (or peptidoglycan) / carbohydrate / lipid / phospholipid / nucleic acid / DNA / RNA ; named bond ; e.g. peptide, glycosidic, ester, phosphodiester [4 max]

138
Q

community

A

all populations / all organisms / all plants + animals (+ microorganisms) ; R all the species

in same, place / ecosystem / area / (common) habitat, (at same time) ;

139
Q

Explain the significance of the following statements in the control of malaria.
(i) The female Anopheles mosquito has been more closely studied with regard to
malaria than the male Anopheles mosquito

A

(only) female feeds on blood / male does not feed on blood ;
female requires blood (protein) for (development of) eggs ;
(only) female carries, pathogen / disease-causing organism / Plasmodium / parasite ;
A (only) female transmits the disease
(only) female is vector ; ora ignore female carries, the disease / malaria

140
Q

Explain the significance of the following statements in the control of malaria.The infective stages of the malarial organism are present in anti-coagulant produced
by the mosquito.

A

anti-coagulant (in saliva) is passed when mosquito, sucks blood / feeds / bites / takes a
blood meal ;
anti-coagulant prevents blood clotting when mosquito, sucks blood / feeds / bites / takes
a blood meal ;

141
Q

Explain the significance of the following statements in the control of malaria After circulating in the blood for a short time, the pathogen enters liver cells of the
newly infected person and then enters red blood cells.

A

in marking accept
Plasmodium / pathogen / causative organism / malarial organism where parasite is given
below
short time (in blood plasma)
for exposure to cells of the immune system / AW ;
next stage(s) of life cycle inside cells ;
A sporozoites into merozoites in liver /
merozoites into schizonts in red blood cells
parasite gains, food / energy, from cells ;
parasite, reproduces / multiplies, inside (liver / red blood) cells ;
damage to / bursting of / lysis of / impaired function of, cells ;
(antimalarial) drugs cannot penetrate (liver / red blood) cells ;
parasite, concealed / ‘hides’, from host immune system ;
A antigen concealment ;
no symptoms, until parasite leaves cells / while parasite is in cells ;
idea that people incubating disease are symptomless ;
A symptomless carriers
idea that treatment unlikely to prevent spread from infected person ;
AVP ; examples
different stages provide problems with drug / vaccine development
AVP ; mode of action of potential drugs – block attachment sites on cells
parasite in blood cells allows testing by taking blood samples
further development of any idea given above

142
Q

Discuss the factors that determine the distribution of malaria worldwide

A

(mainly in) tropics / between the tropics
or
any two named, areas and/or countries, affected ;
e.g. areas (sub-Saharan) Africa, Central America, South America, South Asia, Central
Asia, Middle East, Caribbean
e.g. countries India, Sri Lanka, China, Vietnam, Cambodia, Brazil, Kenya
1 (areas where) both parasite, and, vector / mosquito / Anopheles, are present ;
2 Anopheles / mosquito / vector, survives / breeds / lives, in, hot and humid areas / moist
tropical areas ; ora A standing / stagnant, water
3 parasite, needs to reproduce within the mosquito (at temperatures above 20°C) ;
4 eradicated in some countries / any e.g. (USA, Italy) ;
5 ref to LEDCs and, poor / non-existent, control programmes ;
A poor health facilities / poor drug supplies / AW
6 mosquitoes resistant to, DDT / insecticides / pesticides ;
7 parasite resistant to, chloroquine / drugs ;
8 link between human population density and Anopheles ;
e.g. human activity provides (lots of) breeding sites for Anopheles
9 occurs where named high risk group(s) exist ;
e.g. refugees, HIV-positive pregnant women (more likely to pass HIV to unborn
children), (young) children
10 (outside tropics) disease spread by, travellers / tourists / migrants / refugees ;
11 AVP ;
most cases / over 90% cases, in (sub-Saharan) Africa
not, at high altitude / in deserts
different species of Plasmodium differ in geographical distribution / AW
misdiagnosis (so not reported)
changing pattern linked to, global warming / changes in land use / deforestation /
irrigation / other relevant named
R references to sickle cell

143
Q

x Suggest an explanation for the fact that a different mixture of enzymes is required
to remove the walls of plant cells compared to the walls of fungal cells.

A

idea that plant cell walls and fungal cell walls have different components
fungal cell walls made of, glucans / chitins / fungal cellulose / different components to
plant cell walls ; A peptidoglycan / murein
A plant cell walls contain cellulose, but fungi do not
idea of specificity in context of question
enzymes are specific ;
A specificity explained e.g. both substrates not complementary / shape of active site
specific to one substrate

144
Q

Explain why the person is unlikely to become ill if they are infected by the same pathogen
some months later.

A

active (artificial) immunity ;
2 memory cells / immunological memory ;
3 idea that many specific, B-cells / T-cells / lymphocytes, in the body ;
A large(r) clones of specific, B- / T-cells or lymphocytes
actual invasion by the pathogen
4 fast secondary (immune) response ;
5 fast increase in antibodies / immediate production of antibodies ;
ignore incorrect type of cell secreting antibodies
6 high(er) concentration of antibodies are produced ; A more antibodies produced
7 pathogen destroyed before person becomes ill / AW ; R antigen
A pathogen do not, increase in number / infect cells / AW

145
Q

Some parents decide that their children should not take part in a vaccination schedule.
Suggest how a country-wide vaccination schedule can give protection against infection
to unvaccinated children.

A

(if) most / sufficient / many / AW, people / children, immunised / vaccinated ;
A herd immunity
reduces the pool of infected, people / children, in the, community / population ;
A fewer people can catch disease and be source of infection
A protects those unvaccinated as, disease / illness, does not spread
A less chance of transmission
A pathogen cannot develop in immunised people
A reduced exposure to pathogen

146
Q

Describe and explain the benefits to humans of the presence of nitrogen-fixing bacteria,
such as A. vinelandii, in agricultural land.

A

increase / maintain, nitrogen content of soil ; A add, ammonium / nitrates, to soil
2 increase / maintain, soil fertility ;
3 uptake / absorption, of, ammonium ions / nitrates /fixed nitrogen (by plants) ;
4 (plants use) for, amino acid / protein, production ;
5 increased, growth / yield, of (crop) plants ;
6 ref. feeding, livestock / human populations ;
7 reduced need for fertilisers ;
8 example of environmental benefit of reduced fertilisers ;
9 cost saving from reduced use of fertilisers ;
10 qualified ref. to, Rhizobium / legumes ;

147
Q

The humpback whale is a carnivore, feeding on krill and herring. The herring feed
on krill.In terms of energy transfer, explain how the humpback whale is able to reach such
a large size.

A

plenty of food available / AW;
A feeding on more than one trophic level
2 further detail; e.g. phytoplankton efficient at converting light energy
phytoplankton blooms
little / no competition
ref. efficient feeding mechanism
3 short food chains / fewer links of the food chain;
4 less energy lost overall;
A idea in terms of percent lost at each level
5 few, indigestible / inedible parts;

148
Q

The thickness of blubber in humpback whales decreases during the non-feeding season
and increases during the feeding season.
Suggest explanations for this observation.

A

fat / blubber = triglyceride;
2 fat / blubber / triglyceride, used as energy, store / reserve;
decreases
3 less fat in cells; ora
A fewer fat-filled cells / less adipose tissue
4 mobilised / respired / converted to fatty acids (A glucose), to release energy (during
non-feeding season);
5 energy (from fat mobilisation) used, qualified; e.g. for movement
increases
6 food eaten / during feeding season, conversion to, fat / AW (for storage);
7 ref. thermal insulation;
A idea of prevents heat loss R keeps it warm

149
Q

After infection, the ingested typhoid bacteria are engulfed by phagocytes.
(i) Explain why the phagocytes act only against the bacteria and not against human
cells.

A

1 bacterial (surface) antigens / epitopes, act as, non-self / foreign antigens;
2 human cells have self antigens;
3 (antigens are), proteins / polysaccharides;
4 (non-self antigen) will trigger phagocytosis / phagocytes have receptor
(only) for, bacterial / non-self, antigens / proteins; ora for self antigens
5 ref. to non-self and self antigens containing different sequences of amino acids / self
antigens are products of body’s genotype / AW;
6 idea that phagocytes bind to antibodies complexed with (non-self) antigens (and
human cells will not have bound antibody);

150
Q

Unlike other bacteria, the typhoid bacteria are able to survive and multiply within
the phagocytes.
Suggest an explanation for this observation

A

cmechanism to prevent, phagosome formation / lysosome fusion with phagocytic vacuole
able to withstand attack by (hydrolytic) enzymes
contain enzyme inhibitors
able to degrade (hydrolytic) enzymes
protective capsule

151
Q

With reference to coronary heart bypass surgery, discuss the difficulties in achieving a
balance between prevention and cure.

A

cure for, coronary artery disease / atherosclerosis in artery;
A arteriosclerosis
so less risk of, myocardial infarction / heart attack / AW;
prevention of coronary artery disease to avoid bypass surgery
one example; e.g. no smoking
increase exercise
low, (saturated) fat / cholesterol, diet
reduce alcohol consumption
reduce salt intake
statins
avoid, excessive / AW, sugar
avoid obesity
ref. to difficulties in getting people to change lifestyle to prevent;
disadvantage of, surgical procedure / cure;
accept ora prevention
e.g. invasive / painful
costly medical
lost time / money, by absence from work
risk of complications / graft rejection / infection
risk / graft becoming diseased / collapsing
AVP; e.g. idea that as cure is available, more difficult to encourage prevention

152
Q

State the main difference in the composition of the plant cell wall compared to the
bacterial cell wall.

A

plant cell
cellulose ; treat as neutral ref. to microfibrils / fibres
bacterial cell
murein / peptidoglycan ;
A peptoglycan / polysaccharide and amino acid

153
Q

) Suggest why the sloth and its fur can be described as a small ecosystem.

A

has biotic and abiotic components / biological and physical components ;
A living and non-living components
2 described by use of examples from text ; e.g. water and organisms
A fur as an abiotic factor
3 ref. energy flow / nutrient cycling ;
A described e.g. food web, algae as producers, fungi as decomposers
A food chains look for at least one link
4 ref. interactions / functional entity ; AW e.g. self-contained / self-sustaining /
inter-relationships

154
Q

there are differences in the number of cholera cases reported
between the high economic status country and the low economic status countries.
Suggest three reasons to explain these differences.

A

look for comparative statements
A points if both sides are compared even without ref. to high or low economic country
if not comparative, A if stated as low (or high if ora) economic status country
max 1 if no points stated as low or high but all points themed as low or high
points below are for low economic status countries – ora for high
poor sanitation ;
water
no/ poor water treatment
or
ref. to unable/ do not know to boil water ;
no bottled water
or
have to drink contaminated/ unsafe/ unclean water ;
sewage
inadequate/ poor treatment of sewage
or
sewage contamination of crops ;
medical
no/ poor access to (oral) rehydration therapy ;
vaccines not available/ effective (because poor diet) ;
I vaccination programmes in Canada
antibiotics / drugs / medication not available ;
other
greater number of refugee camps / squats ;
less able to cope after natural disasters ;
less education about disease prevention/ transmission ;
poor hygiene/ described ; e.g. not washing hands after defecating

155
Q

Suggest two reasons why some vaccination programmes may fail to prevent
epidemics.

A

1 required percentage cover not reached/ high percentage cover required/ not enough
people vaccinated ;
2 some do not respond successfully to vaccine ;
3 poor diet/ lack of vitamin A ;
4 poor storage of non-thermostable vaccine ;
5 vaccine not cost-free to population ;
6 inaccessible vaccination stations for some of the population ;
7 ref.to difficulty in giving boosters ;
8 ref.to reluctance to have children vaccinated ;
9 lack of advertising/ campaigns /education to encourage vaccination ;
10 different strain (to the one used in vaccine)/ antigens changing;
R ref.to resistance

156
Q

Outline the response produced by B-lymphocytes on exposure to Morbillivirus in an
individual who already has immunity to measles.

A

ref. to secondary (immune) response ;
2 memory (B), lymphocytes / cells ;
3 recognition of/ binding to antigens ; A clonal selection
A proteins /glycoproteins (on Morbillivirus)
4 clonal expansion/ described ;
5 plasma cells secrete antibodies ;
6 idea of faster production/ higher levels of antibody ;
7 ref. to T (helper)-lymphocytes, release cytokines / stimulate humoral response;
[max

157
Q

Suggest and explain the advantages of using glucose isomerase from T. thermophilus to
produce high fructose corn syrup, rather than using glucose isomerase that has an optimum
temperature of 37 °C.

A

1 maximum / peak of, activity, at lower pH for free enzyme ora
or
free enzyme lower optimum pH ora
or
free enzyme pH 7.4 / 7.5/ 7.6 v immobilised pH 8.5 ;
2 free enzyme has higher/AW activity, at pH, 6 / 6.5/ 7/ 7.5 ; A up to pH 8
ora for immobilised (lower up to pH 8) *
or
free enzyme has higher activity over greater range of pH** (between pH 6–9) ;
3 data to support mp 2 ; *any one pH and comparative activity
** needs two pHs and comparative activities
A manipulated data

4 free enzyme has lower activity, pH 8 to pH 9 ; A after pH 8.0
ora for immobilised (higher after pH 8)
5 data to support mp 4 ; any one pH and comparative activity /manipulated
data
increase to max activity

6 free enzyme has (slightly) steeper increase in activity as pH increases to
pH 7 ; ora
7 data to support mp 6 ;

158
Q

Explain how the action of lysozyme will lead to the destruction of the bacterial cell.

A

breakdown /weaken / digests /AW, cell wall ; A destroyed / damaged
I breaks cross-links / cross-links cannot form
(water enters so) lysis occurs / bursts /AW ;

159
Q

Suggest possible explanations for the decrease in the number of people newly
infected with HIV.

A

stated precaution(s) to reduce risk of infection by
1 using, condoms / femidoms ;
A safe(r) sex / use protection during sexual intercourse
2 abstinence / monogamy / less promiscuity ;
3 not sharing needles / using sterile needles / needle exhange ; A syringes
4 not breast feeding ;
5 (heat) treated blood (products) / testing potential blood donors or donated blood ;
6 ref to contact tracing ;
7 increased awareness of, precautions / risks / transmission ;
8 increased use of (antiviral) drugs reduces transmission ;
9 some strains are less infective than others ;
10 less reporting of new cases ;
11 AVP ; e.g. fewer HIV+ babies born (to HIV+ mothers)
improved, screening / detection, qualified

160
Q

the relationship between

new HIV infections and deaths due to HIV/AIDS. is a postive linear correlation. explain why

A

idea that estimates are subject to large uncertainty / AW ;
idea that needed for any use of the data for planning health services / AW ;
AVP ; e.g. explanation of mp 1 rather than general statement, such as
symptomless carriers
many new cases not diagnosed
many new cases not reported
remote areas

161
Q

the interaction of all living organisms with each other and their non-living environment
in a self-contained location

A

ecosystem

162
Q

Explain how nitrogen from compounds in the dead leaves is made available to the
growing plants.

A

1 protein / amino acids, (in leaf litter) ;
2 ref to, decomposition / decay / decomposers / saprobiotic bacteria or fungi ;
3 deamination ;
4 amino acid converted to, ammonia / ammonium ;
5 ammonia / ammonium, converted / oxidised , to nitrite (ions) / NO2 ;
6 nitrite (ions) / NO2 , converted to, nitrate (ions) / NO3 ;
7 by, nitrification / nitrifying bacteria / named example ; e.g. Nitrosomonas / Nitrobacter
8 nitrate (ions) / NO3 , taken up / absorbed, by mangrove / plant (roots) ;
9 AVP ; e.g. ammonia / ammonium, taken up

163
Q

Explain the importance of taking a complete course of antibiotics.

A

1 (to ensure) all bacteria are, killed / removed / eliminated / destroyed / AW ;
R virus / bacteria and virus
ignore antigen or pathogen or disease
‘all’ may be implied e.g. award if gain mp 2,3,4
2 (so) no reservoir of infection remains / AW / ora ;
3 (disease) cannot be transmitted / cannot infect others / AW e.g. spread / ora ;
4 no recurrence / disease does not return ; in context of same person
5 to reduce chance of / AW, (antibiotic / drug) resistance developing ;
R idea that human becomes resistant to antibiotics
6 ref. to mutation in context of resistance ;

164
Q

State why penicillin, which is an enzyme inhibitor, can be taken by humans.

A

ideas that
(humans) do not have the enzyme for cell wall synthesis ;
A penicillin only inhibits bacterial enzymes
penicillin will not inhibit any human enzyme ;
(human cells) do not have cell walls ;

165
Q

Suggest the effect which penicillin will have on bacterial cells.

A

cell wall synthesis will stop / slow / be inhibited ;
A inhibit, murein / peptidoglycan, synthesis
ref. to uptake of water by osmosis ;
cell cannot withstand osmotic stress / cell cannot withstand turgor pressure /
lysis / bursting / AW ;
A cell wall weakened
bacteria die / are killed / destroyed ;
stops bacteria dividing / reproducing / ‘replicating’ ;
AVP ; e.g. detail of action of penicillin (e.g. prevents cross-links forming),
(penicillin) only works on growing cells

166
Q

Explain why only a small percentage of the energy present at each trophic level is
available to the organisms at the next level.

A

c) energy loss at each level because of
1 inedible parts / not all of the organism can be eaten ;
2 indigestible parts / not all is digested / egestion / faeces ;
3&4 energy / heat, losses from ;;
respiration R energy used for respiration
movement A energy used for movement
excretion
digestion
ignore energy not utilised by plants by e.g. reflection from leaves, etc.

167
Q

Outline what happens to the nitrogen-containing compounds in the organisms at the top
of the food web.

A

1 decomposers / saprotrophs / bacteria / fungi / scavengers / detritivores ;
2 digest / breakdown / hydrolyse, protein / urea ;
3 idea of assimilation in / growth of, decomposers / AW ;
4 deamination ;
5 production of ammonium (ions) / ammonification ; A ammonia / NH3
6 nitrification described or denitrification described ;
A formulae for ammonium ions, nitrite ions and nitrate ions but must be correct including
signs
A nitrification described in terms of ammonium (ions) to nitrate (ions)
ignore nitrogen fixation as used correctly (N2 to fixed N)
ignore uptake of nitrate ions or ammonium ions by plants
do not credit nitrification if any confusion with nitrogen fixation

168
Q

When a pathogen enters the body, a primary immune response occurs. This response
includes the production of antibodies.
Describe the stages in the immune response that lead to antibody being produced
against a specific antigen.

A

antigen recognised as / AW, non-self / foreign ;
accept once for macrophage, B-lymphocyte or T-lymphocyte
A non-self / foreign, antigen leads to immune response
2 idea of phagocytosis leading to antigen presentation ;
3 antigen (on pathogen or APC) binding to, receptor / membrane, of B-cell(s) /
B-lymphocyte(s) ; A clonal selection of B-lymphocytes occurs
4 (helper) T-cell / T-lymphocyte, activate B-cells ; I killer T-cells
A release cytokines to stimulate B-cells
5 B-cells / B-lymphocytes, divide by mitosis ; A replicates / proliferates by mitosis
A clonal expansion of B-cells
6 plasma cells, formed / AW ;
7 plasma cells / B-cells / B-lymphocytes, produce / secrete / AW, antibody /
immunoglobulin / Ig ;

169
Q

Bacteria in root nodules of leguminous plants carry out nitrogen fixation.
Describe how nitrogen that is available to these bacteria can eventually become part of
animal protein.

A

nitrogen, converted / reduced / fixed, to, ammonium / ammonia (in root nodules) ;
A correct equation ( ) () () 2 e6N 8H 2 NH4 2/ NH3
− + + ++ →
R if nitrogen fixation is said to happen in the soil
I nitrogen fixation is carried out by leguminous plant
2 (catalysed by) nitrogenase ; accept if part of equation
3 ATP, hydrolysed / AW ; accept if part of equation
4 ref. to anaerobic conditions ;
5 ammonia (converted) to amino acids to protein (in plants) ;
6 plant protein, digested / hydrolysed / broken down, by animals (into amino acids and
absorbed) ;
7 amino acids used to synthesise (animal) protein ;

170
Q

(iv) Suggest why there are few drugs that have any effect on viruses

A

two from
1 idea that there are few targets for drugs ;
A e.g. virus has no, cell wall / cell membrane /ribosomes
2 no / few, enzymes ;
3 antibiotics only work on, growing / living, cells ;
A viruses have no, metabolism / growth
4 viruses are inside (host) cells / not within reach of antibiotics ;
R if antibodies
5 antibiotics do not work on, protein coat / capsid/ viral envelope ;
I capsule

171
Q

The search for new antibiotics is important because there are many strains of bacteria that
are resistant to antibiotics.
Suggest two ways to reduce the spread of antibiotic resistance.

A

) two from
do not use for viral infections ;
do not use as preventative medicine ;
antibiotics should only be used (for treatment) when necessary ;
carry out antibiotic sensitivity test ;
ensure, correct /effective, antibiotic, prescribed/used ; AW
ensure people take the correct dose ;
ensure people complete the course of their antibiotic ; A ensure people follow the
instructions
ensure people do not use, left-over/other people’s, antibiotics ;
only supply on prescription / not over the counter/AW ;
only use, wide / broad, spectrum antibiotic when pathogen not known ; A ora use
narrow spectrum antibiotic when pathogen is known
use more than one antibiotic (at the same time) ; A mixture of
antibiotics /antibiotics in combination
monitor antibiotics to check that they are effective ;
report cases of antibiotic resistance ;
reporting patterns of antibiotic resistance (temporal and geographical) ;
rotate antibiotics so not used all the time ;
keep some antibiotics to use as a last resort ;
do not use the same antibiotics for animals as for humans ;
reduce use of antibiotics in, food production /(livestock) agriculture ;
use other antimicrobial drugs ;
develop new, types of antibiotics /drugs, to kill bacteria ;
ensure /improve, knowledge of, healthcare professionals /public ; A ref. to
education about awareness of antibiotic resistance
ref. to breaking transmission cycle/ described example of a method ; e.g.
vaccines /good hygiene in hospitals
break transmission cycle of resistant bacteria/ described example ; e.g.
quarantine

172
Q

) Explain why countries that have established vaccination programmes still have cases

A

1 measles introduced by people who caught the disease when abroad ;
A any e.g. tourists / visitors /travellers /returning tourists / migrants /displaced
people
2 idea that herd immunity, needs to be >90%/ is not 100% ;
A herd immunity not achieved
3 some people in these countries have not been vaccinated ;
A too young to receive vaccine /refusal of vaccination /live in remote
places /war zones /AW ;
4 some people do not respond to the vaccine ; A people have weak immune
system / malnutrition
5 some people do not receive booster(s) ;
6 (reconstituted) vaccine is not thermostable /difficult to maintain the cold
chain ;