disease

Question 1

What is meant by the term pathogen?

Answer 1

disease-causing (organism) ;

Question 2

Plasmodium is described as a parasite.

Define the term parasite.

Answer 2

lives , in / on , host ;
gains nutrition / feeds , from (host) ;
at the expense of / harms (host) ;

Question 3

Explain why the human body’s primary defences do not prevent the entry of Plasmodiuminto the body.

Answer 3

mosquito / vector / Anopheles , feeds on blood ;
breaks skin / skin cannot act as barrier / mosquito pierces
skin / mosquito bites skin ;

Question 4

Suggest why malaria is much more common in tropical areas than in other parts of the world.

Answer 4

suitable / AW , climate / temperature , for , mosquito / vector
/ Anopheles ; ora
more mosquitoes live there / AW ; ora
idea of relatively poor so methods of prevention less
effective ;

Question 5

Suggest two reasons why governments in parts of the world other than tropical areas, are also becoming increasingly concerned about malaria.

Answer 5

climate change / global warming / AW , may result in
spread to other parts of the world / AW ;
idea of increased movement of (infected) people ;
idea that (non-malaria) countries fund anti-malaria
measures via international aid ;
resistance of , parasite to drugs / mosquito to
insecticides ;

Question 6

In patients with IDA, anaemia is caused by the destruction of erythrocytes (red blood cells) by phagocytosis.
Suggest why erythrocytes that contain Plasmodium are more likely to be destroyed by phagocytosis than healthy erythrocytes

Answer 6

(different) chemicals that attract phagocytes (released from

infected erythrocytes) ;

Question 7

Antibodies are important biological molecules. Describe how the structure of antibodies allows them to perform their function.

Answer 7

2 light chains and 2 heavy chains / 4 polypeptide
chains ;
variable region allows , binding / attachment , to
antigen ;
two variable regions allow binding of more than
one (of the same) antigen ;
variable region on different antibodies allows specificity
to different antigens ;
constant region allows , recognition by / attachment to /
binding to , (named) phagocytes ;
hinge (region) allows flexibility ;
disulfide , bonds / bridges , hold , polypeptides / light
and heavy chains , together ;

Question 8

Outline the mode of action of antibodies in defending the body against pathogens by describing the processes of neutralisation and agglutination.

Answer 8

neutralisation
cover / block , binding site / antigen / receptor site (on
pathogen) ;
bind to toxins ;
prevent , binding / entry , to (host) cell ;
agglutination
clump / bind together , (many) pathogens ;
(clump) too large to , enter (host) cell / cross
membranes ;
increase likelihood of being consumed by (named)
phagocyte / more can be consumed by phagocyte at
once ;

Question 9

State what is meant by the term health.

Answer 9

mental and physical well-being ;

absence of disease ;

Question 10

The term immunity is often used when describing how vaccines work.
In a piece of school homework a student wrote:“Bacteria can evolve quickly and many are now immune to antibiotics.”
Explain why the student’s use of the word ‘immune’ was incorrect.

Answer 10

immunity involves / bacteria do not have , lymphocytes /
white blood cells / antibodies / memory cells /
plasma cells / an immune system ;
(correct term is) resistant ;
bacteria are unicellular / only multicellular organisms
(can) have an immune response;

Question 11

Why are phagocytes described as a secondary defence against pathogens?

Answer 11

(involved) after , pathogen / AW , has entered the

body ;

Question 12

Why is the response involving phagocytes regarded as non-specific?

Answer 12

(phagocytes) able to, digest / break down / engulf /
target / deal with, a range of / many
different , pathogens ; ora

Question 13

Explain how phagocytes, such as those shown in Fig. 3.1, are able to pass from the blood into the tissue fluid.

Answer 13

lobed / narrow , nucleus ;
(cells) can change shape ;
can squeeze / move / fit / AW , between cells
/ through pores , in (walls of) capillaries ;
histamine makes , capillary walls /
endothelium , leaky ;

Question 14

Bacterial pathogens initially attach to receptors on the surface of phagocytes.
Describe the process by which a pathogen is destroyed after it has become attached to the surface of a phagocyte.
In your answer you should describe clearly the sequence of events that takes place.

Answer 14

(pathogen) engulfed / enveloped / surrounded
by cytoplasm (from phagocyte) ;
endocytosis / phagocytosis ;
(formation of) phagosome / phagocytic
vacuole / phagocytic vesicle ;
(phago) lysosomes ;
(lysosomes / phagosome) move towards /
fuse with (each other) ;
(named) enzyme(s) / lysins / hydrogen
peroxide / free radicals (in lysosomes) ;
(pathogen) digested / broken down /
hydrolysed ;
(to) amino acid / sugar / glucose / fatty acid /
glycerol ;
(break down products) absorbed / AW (into
cytoplasm)
or
unwanted products removed (by exocytosis) ;
cytoskeleton involved in (endocytosis /
movement of vesicles) ;

Question 15

Name the infective agent that causes TB.

Answer 15

Mycobacterium /M. tuberculosis / M. bovis ;

Question 16

Describe how the infective agent that causes TB is transmitted from one individual to another.

Answer 16

droplets (containing pathogen) ;
(released by) coughing / sneezing ;
inhaled by (uninfected) , individual / AW ;

Question 17

Suggest three reasons why the incidence of TB is higher in the low income group.

Answer 17

overcrowded / AW (living space) ;
poorly ventilated (living space) ;
poor diet / malnourished ;
poor health ;
homelessness ;
idea that more likely to consume , meat / milk,
from infected cattle ;
idea of vaccination / medical treatment , more
difficult to access ;

Question 18

Explain why the influenza virus is usually described as a pathogen rather than a parasite.

Answer 18

pathogen causes disease / not all parasites cause
disease ;
(influenza) virus causes a disease / influenza is a
disease ;
parasite gains , nutrition / energy , from host ;
or
(influenza virus) does not gain , nutrients / energy ,
from host ;
virus takes over / AW , (host cell) DNA
/ genetic material ;

Question 19

Define the term immune response.

Answer 19

(response) to an antigen ;

involves , lymphocytes / production of antibodies ;

Question 20

Outline two ways in which antibodies reduce the threat from pathogens.

Answer 20

Z antibodies bind to antigens (on pathogen) ;
otherwise, mark as follows:
N1 neutralisation ;
N2 antibodies , cover binding sites on pathogen / bind to
toxins ;
N3 prevent , binding / entry , to (host) cell ;
A1 agglutination ;
A2 clump / bind together , (many) pathogens ;
A3 (clump) too large to enter host cell / increase likelihood
of being consumed by (named) phagocyte;
the following could be credited
O1 opsonisation ;
O2 activation of complement ;
O3 increase likelihood of being consumed by (named)
phagocyte ;
L1 lysins ;
L2 destroy / AW , pathogens ;

Question 21

In an attempt to reduce the consequences of further outbreaks of influenza, the government encourages immunisation of key groups of people, such as the elderly and children that have another risk factor. Suggest two other groups who should be immunised and explain why immunisation for them would be particularly important.

Answer 21

G1 patients with , HIV+ / AIDS / transplant /
chemotherapy ;
E1 weak immune system / cannot produce (many)
antibodies ;
G2 pregnant women ;
E2 foetus / embryo , has undeveloped immune system
or
antibodies can cross placenta ;
G3 health workers
or
people , living / working , close to outbreak ;
E3 likely to be at (increased) risk (of disease) ;
G4 those with (named) chronic diseases ;
E4 idea of inability to withstand further disease / already
being in poor health ;

Question 22

Other than the direct effects on health or reducing the number of deaths, suggest a reason why spending a large amount of money on immunisation is considered worthwhile.

Answer 22

idea of days lost at work / effect on economy ;
idea of costing more to deal with the ill people (than the cost
of vaccination) ; ora
idea of response to public opinion ;
idea of health service unable to cope ;
idea of eliminating a disease ;

Question 23

Give one reason why, despite being aware of the immunisation programme, some people choose not to be immunised.

Answer 23

idea of:
being too busy / can’t be bothered / feel it is unnecessary ;
lack of trust in government ;
media scare stories ;
concerned about side effects ;
cost implication to individuals ;
allergic to vaccine ;
altruistic reason / other people more deserving ;
fear of needles ;
religious / cultural / ethical , reasons ;

Question 24

The malarial parasite is carried by an insect, the female Anopheles mosquito.
Describe how the mosquito transmits the malarial parasite to a human.

Answer 24

(mosquito), is vector ;
Plasmodium / parasite, present in (mosquito), saliva /
salivary gland ;
idea that infected mosquito, feeds on / bites, human ;
Plasmodium / parasite, passes (from saliva) to blood ;

Question 25

Suggest why the resistance of MRSA to existing antibiotics is of major concern to humans.

Answer 25

MRSA / it, is harder to treat / may become untreatable ;
potential for, disease outbreak / epidemic / pandemic / killing
many people ;
developing new / more powerful, antibiotics, is expensive /
takes time ;

Question 26

Describe the changes in antibody concentration that occur in the patient’s blood during the primary response.

Answer 26

no antibodies detected before 4 days / antibodies appear at 4 days ;
increase then decrease / peak ;
figures for peak with time and antibody concentration ;
decrease less steep than increase / AW ; ora
antibody concentration returns to zero at 27 days ;

Question 27

The patient was subsequently infected with the same pathogen 30 days after the initial infection.
Draw a line on the graph to show the likely concentration of antibodies in the patient’s blood from 30 days onwards.

Answer 27

the drawn line should show
higher peak and steeper initial increase ;
antibodies appear between days 30 and 34 and concentration at 60
days above peak for primary response ;

Question 28

Complete the table below by stating the name and function of each of the region of an antibody

Answer 28

hinge (region) ; flexibility / binding of more than one antigen ;

constant / Fc
(region) ;
attachment / binding , to
phagocytes ;

variable /
hypervariable /
Fab (region) ;
binding / attachment , to
antigens ;

Question 29

Each winter, the UK government recommends that vulnerable members of the public are vaccinated against the influenza (flu) virus.
State two groups of people that the government would consider as being vulnerable.

Answer 29

the elderly / older people ;
‘at risk’ children / young people ;
pregnant women ;
those with compromised immune systems ;
those with chronic diseases ;
health workers ;
poultry workers / pig farmers ;

Question 30

Suggest why the influenza vaccine has to be changed each year.

Answer 30

different strains of the virus / virus mutates (each year) ;
(new strains have) different antigens ;
idea that antibody produced , needs to match new strain /
antigen ; ora

Question 31

state two differences between the primary and secondary immune responses.

Answer 31

secondary response , starts earlier / has shorter delay
before response ; ora
secondary response , more rapid / faster ; ora
secondary response , higher / produces more antibodies ;
ora

Question 32

Describe the role of these memory cells when the influenza virus enters the body.

Answer 32

recognise , virus / antigen / pathogen ;
produce a clone ;
can , change to / form , plasma cells (on infection) ;
make antibodies (against influenza , virus / antigen) ;
responsible for secondary response /
destroy virus before symptoms appear ;
can , change to / form , named T-cell ;

Question 33

State why a doctor would not prescribe antibiotics to treat influenza.

Answer 33

(antibiotics) are, not effective against viruses / effective

(only) against bacteria (and fungi / protozoa ) ;

Question 34

Suggest how Tamiflu® could help to reduce the spread of influenza.

Answer 34

fewer , viruses / pathogens , produced ;
fewer , viruses / pathogens , (in droplets) when ,
sneezing / coughing ;
(as) viruses / pathogens , cannot leave cell ;
(so) cannot , infect / spread to , other cells ;
idea of treating , large / proximate , population ;

Question 35

Suggest why researchers in Nepal concentrated their research on plants that had been used in traditional medicine.

Answer 35

(plants) already identified as likely to have , medicinal
properties / few side effects / AW ;
reduces , time / effort , in finding , plants / active chemicals ;
(possibly) reduces cost ;

Question 36

Identify the infective agent that causes AIDS.

Answer 36

human immunodeficiency virus / HIV ;

Question 37

The government has introduced needle exchange programmes for drug users.
Explain how this may help reduce the transmission of AIDS.

Answer 37

(infective agent), in blood / body fluids ;
idea of: used needles are contaminated ; ora
reduces chance of sharing needles ; ora

Question 38

State three factors that increase the chance of infection with TB.

Answer 38

not vaccinated against TB ;
weakened immune system ;
(lifestyle) e.g. poor diet / lack of protein / malnourished /
smoking / alcoholism ;
homelessness ;
poor ventilation (of housing) / AW ;
overcrowding ;
close contact with people from / visiting, area where TB is
common ;
close / prolonged, contact with individual(s) with TB ;
consumption of milk or beef, from infected cattle / in
developing countries

Question 39

Describe how cytokine molecules can stimulate specific groups of B lymphocytes to divide.

Answer 39

cytokine / interleukin / receptor has, specific / unique,
shape ;
(cytokine / interleukin), binds / attaches / bonds to / fits into,
receptor ;
receptor on (cell surface) membrane (of B lymphocyte) ;
(receptor and cytokine have) complementary shapes ;
activates / stimulates, clonal expansion / mitosis ;

Question 40

State two features of the body that form part of the primary defence.
For each feature explain how it helps to prevent the entry of pathogens and parasites into the body.

Answer 40

skin ;
idea of: physical barrier to prevent entry of microorganisms ;
mucous membrane(s) / goblet cells ;
(produce) mucus to trap, pathogens / parasite ;
OR
mucus ;
traps pathogens ;
cilia / ciliated epithelium ;
remove, pathogen / parasite, laden / AW, mucus ;
blood clotting ;
prevents, pathogens / parasite, entering bloodstream ;
ear wax / nasal hairs ;
traps, pathogens / parasite ;
lysozyme / tears / nasal secretions / saliva ;
kills bacteria / contains antibacterial agent ;
gastric juice / stomach acid ;
kills, pathogens / parasite ;

Question 41

Define the term parasiteand suggest how the threadworm benefits from this relationship.

Answer 41

lives, on / in / in contact with, and harms host ;
takes nutrition from / feeds on (host) ;
warmth ;
protection / safe place / AW ;
allows transmission / spread, to a new host / AW ;

Question 42

suggest two ways in which the cycle of infection could be broken.

Answer 42

wash / clean / disinfect / sterilize, hands ;
not, scratching / touching, of anus ;
drugs to, kill / remove, parasite / eggs ;

Question 43

Suggest two further benefits of using antibiotics.

Answer 43

reduces / prevents (infectious) disease ;
prevent, problems / named problem, with gut ;
digest food more, efficiently / easily / quickly ;
greater proportion of, food / energy,
can contribute to growth ;
reduce risk of transmitting, pathogens / named pathogen, to
humans

Question 44

The use of antibiotics as growth promoters in animal production was banned in the European Union in 2006.Suggest a concern that led to this ban.

Answer 44

(antibiotic) resistant, pathogens / bacteria ;
antibiotics kill useful, bacteria ;
idea of: antibiotic passing into human food ;