CIE Flashcards
Describe how the malarial parasite is transmitted.
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
Explain how using such a vaccine may give long-term immunity to malaria.
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
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.
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
explain why it is difficult to assign some organisms to trophic levels.
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 ;
State two factors that are likely to influence the efficiency of energy transfer by herbivorous copepods.
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
Describe how M. tuberculosis is transmitted from an infected person to an uninfected person
(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) ;
Suggest why fatality ratios for TB are higher in some of the countries than in others.
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 ;
ecosystem
all the organisms and the physical factors that influence them in an area, such as a forest
habitat
a place where an organism lives
community
all the organisms / plants and animals / populations / AW, in the ecosystem / forest / place / area / habitat ;
niche
role of organism in an ecosystem
population
all the organisms of the same species in an ecosystem at the same time
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.
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 ;
reasons for decreased mortality rates
decreasing mortality rate because earlier diagnosis (so fewer die) ; improved, health care / treatment (extends life) ;
Explain how it is possible to reduce the number of deaths during a cholera epidemic in countries such as those in West Africa.
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
Explain why cholera is unlikely to be transmitted in developed countries.
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 ;
Define the term term commnicable disease
caused by pathogen, transmissible / communicable / contagious / transferable / passed from
one person to another ;
Explain why malaria is found in mostly sub Saharan africa, but TB is found everywhere.
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 ;
Explain how vaccination provides immunity as an important part of programmes to control and eradicate infectious diseases
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 ;
Suggest the advantages gained by legumes of having Rhizobium living in their roots
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 ;
Suggest two reasons for the differences shown in estimated life expectancy without HIV/AIDS between the different African countries.
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
List two factors in the prevention and control of HIV/AIDS that would help to improve average life expectancy in the African countries
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 ;
Outline the events that occur in a newly-infected person, which lead to the production of antibodies to HIV.
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
Suggest how a change in the gene can lead to the different enzymes being made
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 ;
what a producers
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
Describe one method of controlling the spread of malaria by targeting its vector and explain its effect
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 ;
Suggest how HIV infection may have led to an increase in malarial infections in sub Saharan africa
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
Explain what is meant by the term nitrogen fixation
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
Explain the importance of this process in making nitrogen from animals available for uptake by plants
) 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 ;
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.
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
State one factor, other than drug therapy, that contributed to the steady decrease in the number of new cases of tuberculosis
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 ;
Outline three reasons why, in many developed countries, the number of new cases of tuberculosis is now increasing
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
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.
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
why is In agriculture, canglucose + nitrate -> water + carbon dioxide + nitrogen be undesirable
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 ;
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
(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
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.
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 ;
Antibiotic resistance is a serious worldwide problem.
Suggest how antibiotics can be used effectively to avoid the development of widespread
resistance in bacteria.
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 ;
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.
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 ;
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.
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 ;
Explain how the virus that causes measles is transmitted
(infected) person, sneezes / coughs / talks / breathes out, (airborne)
droplets / aerosol/ moist air ;
inhaled/ inspire/ breathed in, by uninfected, person ;
Explain the functions of variable region
binds / attaches / combines, to antigen ;
ref. to specificity ;
Explain the functions of disulphide bond
holds, polypeptides /heavy chains / long chains, together ;
maintains, tertiary / quaternary / 3D, structure/ shape ;
Explain the functions of constant region
binds to, receptors / cell (surface) membrane, on, phagocytes / macrophages ;
antigen, marking/ tagging, for, phagocytosis / macrophage action ; AW
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.
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 ;
Describe how V. cholerae is transmitted from an infected person to an uninfected person
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
Explain the importance of nitrogen-fixing organisms, such as in ecosystems
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) ;
Explain what is meant by the term non-self antigen.
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
Outline how B-lymphocytes recognise non-self antigens.
antibody / immunoglobulin/ IgG, on cell surface/on cell membrane ;
(act as) receptors ;
ref. to antigen-binding/AW ;
(shape) specific / complementary, to antigen ;
Outline how plasma cells produce antibody molecules.
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
Describe how antibody molecules are released from the plasma cell.
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 ;
Explain the role of meomory cells
) 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 ;
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
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
Explain the role of nitrogen fixation in the nitrogen cycle.
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 ; [
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.
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) ;
explain how the response to a second infection by this bacterial
pathogen differs from the first.
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
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.
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 ;
Suggest how each of the following reduces the effectiveness of an immune response
Some pathogens are covered in cell surface membranes from their host
pathogen not recognised, as non-self/ foreign ;
pathogen is recognised as self ; A non-foreign
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
no, antibodies /plasma cells / memory (B) cells, produced ;
no humoral response ;
no antigen presentation by B cells ;
name of TB pathogen
type of
organism
Mycobacterium
tuberculosis
bacterium
via, (airborne)
droplets / aerosol(s)
(infection) ;
name of malaria pathogen type of organism mode of transmission
Plasmodium ;
protoctist
(feeding or biting by)
Anopheles / mosquito ;
what are the different modes of transmission of HIV
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
Explain why antibiotics do not affect viruses.
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 ;
suggest the role of viral polymerase
replication of RNA/ to make copies of genes /AW ;
transcription/ production of mRNA ;
detail ; e.g. to make viral proteins ;
outline how monnoclonal antibodies are made
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 ;
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.
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 ;
Explain why tuberculosis (TB) is known as an infectious disease.
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
Outline the role of antibiotics in the treatment of infectious diseases, such as TB
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]
) Suggest what epidemiological evidence would lead to the conclusion that tobacco
smoking is a risk factor for TB.
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