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 Chapter 26
1.
2.
3.
4.
5.
Body defence mechanisms
Which term describes a molecule capable of triggering an immune response?
A
antibody
B
antigen
C
pathogen
D
antibiotic
A humoral response is best described as
A
a response by T lymphocytes to foreign antigens.
B
a response by B lymphocytes to foreign antigens.
C
the production of antibodies by T lymphocytes.
D
the production of antigens by B lymphocytes.
What causes artificial active immunity?
A
deliberately exposing a child to a disease
B
secretion of antibodies in milk
C
inoculation with a vaccine
D
injection of monoclonal antibodies
Which of the following best describes antibodies?
A
made by phagocytes and specific to one antigen
B
made by lymphocytes and specific to one antigen
C
made by leucocytes and non-specific
D
made by phagocytes and non-specific
What are antigens?
A
substances that stimulate the production of antibodies
B
harmful bacteria that are contained in vaccines
C
substances that attack any foreign material when it enters the body
D
harmful bacteria that are found in some foods
1
6.
7.
8.
Which of the following is an immune response?
A
T lymphocytes secreting antigens
B
T lymphocytes carrying out phagocytosis
C
B lymphocytes combining with foreign antigens
D
B lymphocytes producing antibodies
Which of the following is an example of active immunity?
A
antibody production following exposure to antigens
B
antibodies crossing the placenta from mother to foetus
C
antibodies passing from the mother’s milk to a suckling baby
D
antibody extraction from one mammal to inject into another
Some infectious diseases are treated by injecting the patient with antibodies after
they have been exposed to the disease.
What type of immunity is this?
A
B
C
D
9.
artificial and active
artificial and passive
natural and active
natural and passive
An allergy is an overreaction of the immune system to foreign substances. Which
of the following substances would be at high levels during allergic reactions?
A
B
C
D
pathogens
antibiotics
antibodies
enzymes
2
10. The diagram below shows a molecule involved in body defence.
Which of the following statements about this molecule is not correct?
A
It is a protein molecule.
B
C
D
It is produced by a plasma cell.
It can combine with specific antigens.
It can activate killer T cells to carry out phagocytosis.
11. Which of the following comparisons between B cells and T cells is not correct?
B cells
T cells
A
mature in bone marrow
mature in thymus gland
B
responsible for humoral immune
responsible for cell-mediated
responses
immune responses
give rise to plasma cells and
give rise to helper T cells, killer T
memory B cells
cells and memory T cells
activated by antigens and helper T
activated by infected cells or
cells
cancer cells.
C
D
12. Which of the following statements about cell-mediated immune response is not
correct?
A
Killer T cells cause the infected cells to lyse.
B
Helper T cells activate B cells to carry out humoral immune response.
C
Helper T cells are activated by antigens on pathogens.
D
T cells secrete lymphokines to activate phagocytes.
13. In mammals, bacteria in food are killed by
A
saliva.
B
gastric juice.
C
bile.
D
mucus.
3
14. Our skin prevents the entry of pathogens with the help of
A
mucus-secreting cells.
B
ciliated epithelial cells.
C
dead cells.
D
phagocytes.
15. Which of the following kills specific pathogens only?
A
B
tear
antibody
C
D
phagocyte
gastric juice
16. Antibodies take part in body defence by
(1) lysing the pathogens.
(2) attaching to the antigens.
(3) engulfing the pathogens.
A
C
(1) only
(1) and (2) only
B
D
(2) only
(2) and (3) only
17. Which of the following substances can stimulate the body to produce an immune
response?
(1) bacterial toxins
(2) dead pathogens
(3) live pathogens
A
B
C
D
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
18. Which of the following is not a chemical barrier that prevents pathogens from
entering the body?
A
B
C
D
sebum
gastric juice
antibody
saliva
4
19. Pathogens that enter the respiratory tract are
(1) trapped by mucus.
(2) removed by the beating action of cilia.
(3) killed by lysozyme.
A
B
C
D
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
20. Antibodies are produced by
A
phagocytes.
B
C
D
plasma cells.
killer T cells.
helper T cells.
21. Which of the following comparisons between primary and secondary responses
is not correct?
A
B
C
D
Primary response
lasts for a shorter period of time
produces a smaller amount of
antibodies
Secondary response
lasts longer
produces a larger amount of
antibodies
effected by stimulation of B cells
and T cells
shorter latent period
effected by stimulation of memory
B cells and memory T cells
longer latent period
22. Vaccination is
A
B
C
D
a kind of natural immunity.
a kind of artificial immunity.
always effective in preventing a disease.
the injection of a small amount of active pathogens into our body.
23. The formation of a blood clot over the wound
(1) cuts off the supply of oxygen to the invading pathogens.
(2) prevents excessive blood loss.
(3) blocks the entry of pathogens through the wound.
A
C
(2) only
(1) and (3) only
B
D
(3) only
(2) and (3) only
D
5
Directions: Questions (24) and (25) refer to the diagram below, which shows a white
blood cell killing a pathogen.
pathogen
24. This white blood cell is
A
B
C
D
a killer T cell.
a memory B cell.
a plasma cell.
a phagocyte.
25. The white blood cell kills the pathogen by
A
enzymes.
B
C
D
antibodies.
antitoxins.
antibiotics.
26. People with severe burns suffer from infections easily because
A
B
C
D
antibodies are lost from the body.
no more cells are available for the production of antibodies.
the sebaceous glands can no longer produce sebum.
pathogens can enter the body easily through the open wounds.
27. Which of the following happen in an inflammatory response?
(1) More blood flows to the affected area.
(2) Pus forms inside the wound.
(3) Tissue fluid accumulates in the affected area.
A
C
(1) and (2) only
(2) and (3) only
B
D
(1) and (3) only
(1), (2) and (3)
6
28. The diagram below shows the concentration of antibodies in the blood in two
concentration of antibodies
consecutive immune responses induced by the same antigen.
second
response
first
response
time
Which of the following statements about the two responses is correct?
A
B
C
D
The antibodies produced in the first response are more powerful.
The first response cannot kill pathogens.
The first response is caused by vaccination.
The second response provides a stronger immunity against pathogens.
29. Which of the following are white blood cells?
(1) memory cells
(2) lymphocytes
(3) phagocytes
A
B
C
D
(3) only
(1) and (2) only
(2) and (3) only
(1), (2) and (3)
7
Directions: Questions (30) and (31) refer to the diagram below, which shows the
concentration of antibodies in blood
change in antibody concentration in the blood of a person after injection of a vaccine.
time
injection of vaccine
30. Referring to the diagram, which of the following occurred after the injection of
the vaccine?
(1) activation of B cells
(2) formation of memory B cells
(3) release of lymphokines
A
B
C
D
(2) only
(3) only
(1) and (2) only
(1), (2) and (3)
8
31. Which of the following graphs correctly shows the change in antibody
concentration after injection of a booster?
concentration of
antibodies in blood
B
concentration of
antibodies in blood
A
time
time
concentration of
antibodies in blood
D
concentration of
antibodies in blood
C
time
time
32. Which of the following statements about body defence mechanisms is correct?
A
B
C
D
Phagocytosis is an example of specific defence mechanisms.
Mucus lining the respiratory tract is a chemical barrier.
Sebum secreted by sweat glands acts as a natural antiseptic.
Hydrochloric acid in gastric juice can kill pathogens.
33. Which of the following is/are not action(s) of antibodies?
(1) stick the pathogens into clumps
(2) prevent the pathogens from secreting toxins
(3) kill the pathogens by lysis
A
C
(1) only
(1) and (2) only
B
D
(2) only
(2) and (3) only
9
34. Which of the following statements about the process shown in the diagram below
is not correct?
cell
pathogen
A
B
C
D
The process is called phagocytosis.
The process is carried out by killer T cells.
In the process, pathogens are digested by enzymes produced by the cells.
The process is always associated with an inflammatory response.
35. Which of the following statements about an inflammatory response is/are
correct?
(1) Arterioles dilate and tissue fluid accumulates in the infected area.
(2) Capillaries in the infected area decrease their permeability.
(3) Pus is secreted to digest pathogens.
A
C
(1) only
(1) and (2) only
B
D
(2) only
(1) and (3) only
36. Which of the following statements about vaccination is not correct?
A
B
C
Vaccines may contain weakened or killed pathogens.
Vaccination is not effective for viral infections.
Vaccination makes use of the specificity and immunological memory of the
specific defence mechanisms.
D
Vaccination stimulates the body to produce a primary response.
10
37. The diagram below shows the concentration of antibodies in the blood of a
concentration of antibodies
person infected with the same pathogen twice.
first infection
second infection
day after
first
infection
What can be deduced from the diagram?
A
B
More pathogens are involved in the second infection.
The pathogens in the first infection were inactivated before entering the
body.
C
D
More phagocytes were involved in the second infection.
Plasma cells were produced faster in the second infection.
11
Short questions
1.
Describe the processes involved in blood clotting.
2.
a
(6 marks)
The following diagram shows phagocytosis in action.
stage 1
stage 2
stage 3
nucleus
P
b
Q
Name the cells labelled P and Q on the diagram.
(2 marks)
i
Give one way active immunity can be produced.
(1 mark)
ii
Give one advantage of active immunity.
(1 mark)
3.
Describe the production of antibodies as the response of the immune system to
the entry of pathogens into the body.
(6 marks)
4.
Discuss the role played by phagocytic leucocytes (phagocytes) in protecting the
body from pathogens.
(5 marks)
5.
Name the following:
a
the defence mechanism that seals the wounds to prevent the entry of
pathogens.
(1 mark)
b
the defence mechanism that is characterized by redness, swelling and pain.
(1 mark)
c
the type of white blood cells that carry out non-specific defence mechanism.
(1 mark)
12
6.
Read the passage below and answer the questions that follow.
After reproducing in the human liver, malaria parasites infect red blood
cells and stay inside. They synthesize a protein that appears on the surface of
red blood cells. This protein anchors the infected red blood cells to the wall of
blood vessels, preventing them from being destroyed by the spleen.
This surface protein can initiate an immune response. To deal with this
problem, the parasite frequently changes the structure of the protein.
7.
8.
a
Describe how the surface protein on the infected red blood cells triggers a
humoral immune response.
(4 marks)
b
Explain why frequently changing the structure of the surface protein is an
effective method to prevent being destroyed.
(3 marks)
State one example for each of the following:
a
b
c
d
Active natural immunity
Active artificial immunity
Passive natural immunity
Passive artificial immunity
(1 mark)
(1 mark)
(1 mark)
(1 mark)
a
State two differences between active and passive immunity.
(2 marks)
b
The diagram below shows the structure of an antibody.
X
polypeptide chain
i
Name region X.
ii
With reference to the structure of antibodies, explain why each
antibody only acts against one type of antigen.
(1 mark)
(2 marks)
13
9.
The diagram below shows the change of a lymphocyte in response to the
invasion of measles virus.
X
Y
Z
P
a
i
Name the molecules on the surface of measles virus that stimulate the
body to develop an immune response.
(1 mark)
ii
Name the processes carried out by X that lead to the formation of Y
and Z.
(1 mark)
iii
Y is responsible for long-term immunity to measles. What is Y?
(1 mark)
iv
b
Name molecule P produced by Z.
(1 mark)
A doctor claimed that there is a link between MMR vaccine and autism
(自閉症).
The diagram below shows the number of children having autism in
a country from 1988 to 1996. MMR vaccine was given to children between
number of children developed autism
(per 10 000 children)
1990 and 1993.
140
120
100
80
60
40
20
0
1988
1989
1990
1991
1992
1993
1994
1995
1996
year
Using the data shown in the diagram, determine whether MMR vaccine is
related to the development of autism. Explain briefly.
(2 marks)
10. To find out the functions of T cells in humans, a group of scientists used a type
of mice that cannot generate mature T cells in an investigation. These mice
14
cannot carry out some immune responses.
a
b
c
d
Where do T cells mature in the human body?
(1 mark)
Which type of immune responses are T cells responsible for?
(1 mark)
State one disease that these mice are likely to suffer from.
(1 mark)
When T cells are activated, they multiply and differentiate into two other
types of cells. Name the two types of cells and give a function of each.
(4 marks)
11. Describe how B cells take part in immune responses.
(4 marks)
12. Smallpox vaccine contains live cowpox virus. Explain why injecting cowpox
virus enhances immunity to smallpox.
(3 marks)
13. Use the words below to complete the following paragraph.
antibodies
active
antigen
short
(4 marks)
passive
long
Newborn babies are immune to certain infectious diseases if they are fed with
breast milk which contains a
from the mother. This is an example of
b
immunity. Since no c
is introduced, the body does not
develop immune response. Therefore, this kind of immunity is of d
duration.
14. The diagram below shows the structure of human skin.
15
X
Y
a
Name structures X and Y.
(2 marks)
b
State one way in which each of the structures in a is involved in defending
the body against invasion by pathogens.
(2 marks)
15. Vaccines against influenza are needed to be injected each year, while only a
single shot of pneumonia vaccine is needed in a person’s lifetime. Suggest two
reasons for the difference.
(3 marks)
16. The diagram below shows how the immune system responds when it comes into
contact with a pathogen.
exposure to an antigen
P activated
Q activated
R activated
multiply and differentiate to form S
multiply and differentiate to form U
antibodies produced
destroy antigens directly
a
b
Identify cells P, Q, R, S and U.
(5 marks)
Apart from S and U, state two other types of white blood cells that are
produced by P and R in the immune response.
(2 marks)
16
17. Complete the table below, which shows some non-specific defence mechanisms
in humans.
(7 marks)
Physical
a
barriers
Cilia and b
that covers the whole body
lining the respiratory tract
c
secreted by sebaceous glands
Chemical
d
secreted by stomach
barriers
e
secreted by tear glands and f
secreted by salivary glands
Secretions from the g
18. Read the passage below and answer the questions that follow.
The immune system is normally directed towards invading pathogens.
However, for the patients suffering from autoimmune diseases, the immune system
mistakes the body tissues as foreign antigens and produces antibodies against them.
Many of the patients receive immunosuppressive medications to control their
diseases.
a
Name the type of immune response that is responsible for production of
antibodies.
(1 mark)
b
Suggest two ways by which antibodies attack the body tissues.
(2 marks)
c
Suggest one side effect of immunosuppressive medications.
(1 mark)
19. Certain medical treatments can help our bodies defend against pathogens.
a
Antibodies can be injected into the body to fight against pathogens. Is this
method specific or non-specific? Why?
b
(2 marks)
How does vaccination defend the body from an attack of pathogens? Why is
this a better method than the method in a?
(5 marks)
17
Structured questions
20. The following graph shows how antibodies in John’s blood increase when he is
number of antibodies
produced by body
infected with a disease such as measles.
time (week)
infection
a
Use the information provided to explain why:
i
John’s immunity is active.
(1 mark)
ii
Active immunity is described as being permanent.
(1 mark)
iii
The symptoms of measles do not disappear immediately.
(1 mark)
b
Describe how antibodies combat microorganisms.
c
Antibody levels can also be raised by vaccinations, e.g. MMR.
(2 marks)
Most doctors and the government encourage its use, while some parents
object. Give one medical reason for using MMR and one against.
(2 marks)
d
John’s sister Mary is to visit Africa for the first time. Explain why she
should have a number of new vaccinations before travelling.
(2 marks)
18
21. a
The MMR vaccine protects against mumps, measles and rubella.
However, in 1998 it was reported that there could be a link between the
MMR vaccine and autism (自閉症). By 2004 this was disproved and the
following year showed the use of MMR vaccine rising to 1998 levels.
i
Suggest how the report in 1998 may have affected the number of
children using the vaccine.
ii
(1 mark)
Suggest one way in which the Health Service encourages parents to
have their children vaccinated with the MMR vaccine.
b
(1 mark)
MMR and some other vaccinations are given in two stages - an initial
vaccination followed by a booster some time later. The following diagram
shows the antibody level following an initial vaccination.
level of antibody
level of antibody required
to reach immunity
initial
vaccination
c
booster
time (year)
i
Complete the diagram to show the effect of the booster on antibody
levels.
(2 marks)
ii
Explain why the immunity produced by vaccinations is active
immunity.
(2 marks)
iii
Vaccines contain modified microorganisms. Why must they be
modified?
(1 mark)
John went to his doctor with a pain in his chest. The doctor told him he had
a chest infection and prescribed him an antibiotic.
Give one reason why an antibiotic will be more effective than a vaccine to
combat the chest infection.
(1 mark)
19
22. The MMR vaccine can protect children against three diseases caused by viruses.
One of these diseases is rubella.
a
b
c
i
Name the other two diseases that can be prevented by injecting MMR
vaccine.
(2 marks)
ii Explain why rubella cannot be treated with antibiotics.
(1 mark)
Some parents are concerned about the risk of receiving the vaccine.
i
Explain why children may develop disease symptoms after
vaccinations.
(2 marks)
ii State one other risk of vaccinations.
(1 mark)
The MMR vaccine was introduced in 1988. The diagram below shows the
number of children infected with rubella in a country after the introduction
number of children infected
with rubella
of MMR vaccine.
1988
1989
1990
1991
1992
1993
1994
1995
year
i
Using the data shown in the diagram, comment on the effectiveness of
the MMR vaccine.
(2 marks)
ii
State how the number of children infected with rubella may change if
the parents refused to let their children to receive MMR vaccine.
(1 mark)
23. A person was bitten by a dog. Blood immediately came out from the wound. A
scab was formed on the wound after some time.
a
b
c
d
Explain how the scab was formed.
(2 marks)
State two other changes that can be observed at the wound.
(2 marks)
Describe how these two changes occurred.
(2 marks)
The person got an infection from the bite and was given an injection as a
treatment. Suggest what may be present in the injection for treating the
infection.
(1 mark)
20
annual number of deaths from
tuberculosis (per 1000 people)
24. The graph below shows the number of deaths from tuberculosis in a country.
70
60
50
40
30
20
10
0
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
year
Invention of vaccine and antibiotics effectively decreased the number of deaths
from tuberculosis from 1900 to 1990.
a
In relation to the use of antibiotics, explain the trend from 1990 to 2000.
(3 marks)
b
Describe how vaccination enhances the immunity to tuberculosis.
(5 marks)
25. Read the passage below and answer the questions that follow.
Chickenpox is an infectious disease caused by a virus called Varicella
zoster. The virus mainly affects the skin and the lining of the mouth and throat.
After the entry of the virus into the body, there is an incubation period of about
14 to 21 days. Groups of small, red, itchy and fluid-filled spots appear on many
parts of the body. After a few days the spots break open and scabs form. It takes
7 to 10 days for recovery.
a
The virus enters the body through the respiratory tract or digestive tract.
Describe the body defence mechanisms at these two sites.
b
If the spots are scratched, pus may form and the wounds may become
painful. Explain why.
c
(4 marks)
(4 marks)
Although antibiotics cannot kill viruses effectively, they are sometimes
given to children with chickenpox. Suggest one reason for this. (2 marks)
21
26. By testing for the presence of a particular antibody in the blood, we will know
whether a person has infected with a certain disease before.
a
b
c
d
e
27. a
What are antibodies?
(1 mark)
Name the type of cells that produces antibodies
(1 mark)
State the actions of antibodies against pathogens.
(3 marks)
Why is the antibody test an accurate method?
(2 marks)
If a pathogen the body was previously exposed to invades the body again,
how will the antibody level in the blood change? How can this prevent the
person from getting the disease again?
(2 marks)
Without protection by the skin, serious burnt victims may suffer from
serious infections and probably die eventually. Explain how the skin
protects the body from infections.
b
(2 marks)
If bacteria enter the body through a wound, an inflammatory response may
result. Describe and explain the events that occur during an inflammatory
response.
c
Besides wounds, list three other sites through which pathogens enter the
body.
28. a
(5 marks)
(3 marks)
Describe how an injection of a vaccine causes the body to produce
antibodies.
(3 marks)
b
X was vaccinated for a certain disease but Y did not. State two differences
in the immune responses of X and Y when they are invaded by the antigen
same as the one in the vaccine later.
(2 marks)
c
Under the immunization programme in Hong Kong, vaccines like BCG
vaccine and MMR vaccine are compulsory for the children.
i
Suggest two advantages of compulsory vaccination for the community.
(2 marks)
ii
Suggest two disadvantages of compulsory vaccination for the
individual.
(2 marks)
22
29. The diagram below shows some structures of human body.
W
X
Y
Z
a
State the physical and chemical barriers at W.
b
Describe the defence mechanisms at
c
i
X.
(3 marks)
ii
Y.
(1 mark)
An inflammatory response occurs at Z. Explain why this area is red, hot and
swollen.
d
(2 marks)
(3 marks)
Are the defence mechanisms in a, b and c specific or non-specific?
(1 mark)
30. A man caught a cold and he transmitted the disease to his wife a few days later.
After he had recovered, his wife was still quite ill. However, he did not get the
disease from his wife anymore.
a
Explain why the man did not catch a cold from his wife.
(4 marks)
b
Explain why the man may catch a cold again later.
(2 marks)
c
The cold virus enters human bodies through the respiratory tract and
digestive tract. State the defence mechanisms in these two tracts that
prevent the entry of pathogens.
(4 marks)
23
31. Read the passage below and answer the questions that follow.
Hepatitis B is caused by hepatitis B viruses, which are present in the blood and
other body fluids of infected people. Vaccines for hepatitis B have been available
since 1982. Three shots of vaccines are required to provide adequate immunity to
the disease.
a
What substance in the vaccines provides immunity to hepatitis B?
(1 mark)
b
Explain how people acquire immunity to hepatitis B through vaccination.
(4 marks)
c
d
People who are ill should not receive vaccines. Explain why.
(2 marks)
Suggest two other measures to prevent the transmission of hepatitis B.
(2 marks)
32. a
Draw a curve on the graph below to show the change in antibody level in
the blood during primary and secondary responses. Label the periods of the
(2 marks)
antibody level in blood
two responses on the graph.
time
first attack
by pathogen
second attack
by pathogen
b
Explain the shape of the graph.
c
Explain how vaccination makes use of primary and secondary responses to
prevent infectious diseases from developing.
d
(4 marks)
(3 marks)
State one other method of developing artificial immunity apart from
vaccination.
(1 mark)
24
Essays
33. Explain the production of antibodies.
(8 marks)
34. Discuss the advantages and disadvantages of vaccination.
(11 marks)
35. Describe how vaccination enhances the immunity of an individual.
(9 marks)
36. Discuss the problems associated with the use of influenza vaccines.
(10 marks)
37. State the similarities and differences between the primary and secondary
responses.
(9 marks)
25
Answers
Questions No.
Key
Question No.
Key
1.
B
31.
C
2.
B
32.
D
3.
C
33.
B
4.
B
34.
B
5.
A
35.
A
6.
D
36.
B
7.
A
37.
D
8.
B
38.
9.
C
39.
10.
D
40.
11.
D
41.
12.
C
42.
13.
B
43.
14.
C
44.
15.
B
45.
16.
C
46.
17.
D
47.
18.
C
48.
19.
A
49.
20.
B
50.
21.
D
51.
22.
B
52.
23.
D
53.
24.
D
54.
25.
A
55.
26.
D
56.
27.
D
57.
28.
D
58.
29.
D
59.
30.
C
60.
26
1.
Tissue is damaged / cut / bruised.
1m
Blood platelets release clotting factors.
1m
Plasma contains soluble fibrinogen.
1m
Fibrinogen is converted into fibrin
1m
and forms a net of fibres trapping blood cells.
1m
Formation of a blood clot prevents blood loss / entry of bacteria / pathogens.
1m
a
P: phagocyte
1m
Q: microorganisms / bacteria / fungi / viruses / pathogens
1m
i
Vaccination / have had a disease
1m
ii
Active immunity is permanent / long lasting.
1m
2.
b
3.
Pathogen is a disease-causing organism or virus.
1m
Antigen is a foreign protein / molecule in the body.
1m
Helper T cells and antigens activate B cells to divide and clone
1m
into plasma cells which produce antibodies.
1m
Antibodies bind to the antigens.
1m
Memory cells are also produced for long-term protection.
1m
Phagocytes present in the blood leave the capillaries and go into body tissues.
1m
They concentrate at the sites of infection.
1m
They are attracted to pathogens
1m
and respond to antibodies.
1m
They kill / digest pathogens.
1m
a
Blood clotting
1m
b
Inflammatory responses
1m
c
Phagocytes
1m
4.
5.
27
6.
a
b
The surface protein on the infected red blood cells acts as an antigen.
1m
B cells are activated by the antigen and helper T cells.
1m
B cells multiply and differentiate into memory B cells and plasma cells.
1m
Plasma cells produce antibodies to act against the antigen.
1m
Memory cells are specific.
1m
After changing the structure of the surface protein, memory cells can no longer
recognize the antigen.
1m
Secondary response which is faster, stronger and lasts longer will not be
triggered.
1m
a
Recovery from an infection
1m
b
Vaccination
1m
c
Diffusion of antibodies from the mother’s blood to the embryo’s blood in the placenta
7.
/ passing of antibodies from mother to baby through breast-feeding
1m
d
Injection of antibodies
1m
a
Active immunity lasts longer while passive immunity lasts for a shorter period of
8.
time. /
The start of active immunity is slow while the start of passive immunity is fast. /
Active immunity involves antigens / the production of memory cells / immune
b
responses while passive immunity does not. (any 2)
1m x 2
i
Antigen-binding site
1m
ii
Antigen-binding sites of an antibody are specific to one type of antigen.
1m
Each antibody can only combine with one type of antigen to form an
antigen-antibody complex.
1m
28
9.
a
b
i
Antigens
1m
ii
Mitotic cell division and differentiation
1m
iii
Memory B cell
1m
iv
Antibody
1m
There is no relationship between MMR vaccine and autism. / Receiving MMR
vaccine does not cause the development of autism.
1m
The number of children having autism from 1990 to 1993 did not show a sharp
increase. / The number of children having autism was higher from 1994 to 1996
during which vaccination was stopped.
1m
a
Thymus gland
1m
b
Cell-mediated immune responses
1m
c
Cancer / viral infections
1m
d
Memory T cells
1m
10.
They are responsible for remembering the antigens / responsible for secondary
responses.
1m
Killer T cells
1m
They bind to antigens on the surfaces of infected cells or cancer cells and cause
lysis of the cells.
1m
11.
B cells are activated by antigens and helper T cells.
1m
They divide by mitotic cell division and differentiate into plasma cells and memory B cells.
1m
Plasma cells release antibodies.
1m
Memory B cells remain in the body for a long time for a secondary response.
1m
Cowpox virus has similar antigens as smallpox virus.
1m
Memory cells recognizing these antigens are produced after vaccination.
1m
12.
A secondary response can be developed if the person is later invaded with smallpox
virus.
1m
29
13.
a
antibodies
1m
b
passive
1m
c
antigen
1m
d
short
1m
a
X: layer of dead cells / outermost layer of epidermis
1m
Y: sebaceous gland
1m
14.
b
X: The layer of dead cells forms a physical barrier that prevents the pathogens
from entering the body.
1m
Y: Sebum secreted by sebaceous glands is a natural antiseptic that kills
pathogens.
1m
15.
Influenza is caused by viruses while pneumonia is caused by bacteria.
1m
There are many different influenza viruses while there are only a few strains of
pneumonia bacteria. /
Antigens on different types of influenza viruses are very different while antigens on
different strains of pneumonia bacteria are similar. /
Influenza viruses have a high mutation rate but pneumonia bacteria have a low mutation
rate. (any 2)
1m x 2
a
P: B cells
1m
Q: helper T cells
1m
R: T cells
1m
S: plasma cells
1m
U: killer T cells
1m
Memory B cells
1m
Memory T cells
1m
16.
b
30
17.
a
Skin
1m
b
mucus
1m
c
Sebum
1m
d
Gastric juice
1m
e
Tears
1m
f
saliva
1m
g
vagina
1m
a
Humoral immune response
1m
b
Antibodies attach to the antigens on the cells and lyse the cells.
1m
18.
Antibodies attach to the antigens on the cells and help the phagocytes engulf the
cells more easily.
c
1m
Immunosuppressive medications suppress the ability of the immune system to
fight against pathogens.
1m
It is specific.
1m
19.
a
Antibodies combine with antigen to act against pathogens. Therefore, the antibodies
b
injected must fit the shape of the antigen.
1m
Vaccination is the injection of weakened or killed pathogens into the body.
1m
Antigens in vaccines stimulate the body to produce a primary response.
1m
Memory cells that remember specific antigen are produced.
1m
When attacked by the same pathogen again, the body will develop a secondary
response to destroy the pathogen quickly.
1m
The effect of vaccination lasts longer when compared with the injection of antibodies.
.
1m
31
20.
a
i
Antibodies are produced by the body.
ii
The level of antibody remains high. /
1m
The immunity lasts long. /
Memory cells remain in the body. (any 1)
iii
It takes time for the level of antibody to rise to a level that is enough to kill all
the pathogens.
b
1m
1m
Microorganisms are immobilized / are clumped together. /
Antibodies attach to microorganisms to help phagocytes engulf the
microorganisms. /
c
d
Antibodies lyse the microorganisms. (any 2)
1m x 2
For: Vaccination can help prevent infection.
1m
Against: Vaccination may cause side effects.
1m
Africa may have diseases that Mary was not previously exposed to.
1m
No antibodies present in Mary’s body to combat these diseases.
1m
i
The number of people receiving MMR vaccine may have decreased.
1m
ii
By advertising / by offering free vaccinations / to give vaccinations in school.
21.
a
1m
b
i
Level of antibody rises faster than initial vaccination.
1m
The level of antibody reaches the level of immunity and remains above the
level of immunity.
ii
The body produces antibodies to act against antigens in the vaccines. 1m
The body possesses memory cells after vaccination.
iii
1m
1m
The microorganisms are modified so that they become harmless to the
body.
1m
c
Antibiotics can kill the pathogens faster / combat wider range of infections. 1m
a
i
22.
b
Mumps
1m
Measles
1m
ii
Antibiotics can kill only bacteria but not viruses.
1m
i
Vaccines may contain pathogens which stimulate the body to produce a
primary response.
1m
32
The primary response is slow. Disease symptoms may develop before the
body produces enough antibodies to act against the pathogens.
ii
1m
Vaccine may cause allergic reactions. /
Vaccine may cause side effects like redness and swelling in the skin. 1m
c
i
MMR vaccine is effective in enhancing the immunity of the children against
rubella.
1m
The number of children infected with rubella decreased after the introduction
ii
of MMR vaccine.
1m
The number of children infected with rubella may increase.
1m
23.
a
Blood platelets released chemicals that turn the soluble fibrinogen in plasma into a
net of insoluble fibrin.
1m
This net of fibrin trapped blood platelets, red blood cells and white blood cells to
form a blood clot.
b
c
1m
The wound became red / became swollen / yellowish liquid (pus) was formed.
(any 2)
1m x 2
Any two (should match with answer in b):
1m x 2
Red:
Arterioles dilated, thus more blood flowed to the infected area.
OR
Swollen:
Arterioles dilated and the permeability of capillaries increased, thus tissue fluid
accumulated in the infected area.
OR
Yellowish liquid (pus) formation:
Pathogens were killed by the phagocytes / phagocytes died and their remains
formed pus.
d
Antibodies / antibiotics
1m
a
The number of deaths increased from 1990 to 2000.
1m
24.
The indiscriminate use of antibiotics speeds up the development of antibiotic
resistant strains of tuberculosis bacteria.
1m
Infection of some strains of tuberculosis bacteria cannot be treated, thus the
death rate increased.
1m
33
b
Vaccine against tuberculosis contains an antigen of tuberculosis bacteria.
1m
The antigen stimulates the body to develop a primary response.
1m
Memory cells remain in the body after the primary response.
1m
The body develops a secondary response when it is invaded with the tuberculosis
bacteria.
1m
Memory cells can respond quickly by multiplying and differentiating into a large
number of plasma cells and killer T cells to kill the bacteria.
1m
25.
a
Cells in the epithelium of the respiratory tract are closely packed to form a physical
barrier against the entry of pathogens.
1m
The mucus traps pathogens from inhaled air.
1m
Cilia lining the trachea and bronchi move the trapped pathogens up the bronchi to
b
the pharynx by the beating action.
1m
Hydrochloric acid in gastric juice in stomach kills the pathogens.
1m
Bacteria that enter the body through the wounds trigger an inflammatory response.
1m
Arterioles in the infected area dilate and capillaries there increase their
permeability.
1m
Accumulation of tissue fluid causes pain in the infected area.
1m
More phagocytes come out of the capillaries to engulf and kill the bacteria. Pus is
c
the remains of killed bacteria and dead phagocytes.
1m
Antibiotics are used to prevent infection caused by bacteria
1m
which enter the body through the wounds if the spots are scratched heavily. 1m
26.
a
Antibodies are Y-shaped protein molecules that are involved in body defence.
1m
b
Plasma cell
1m
c
Antibodies attach to the antigens on the pathogens and lyse the pathogens. 1m
Antibodies attach to the antigens on the pathogens and help phagocytes engulf the
pathogens more easily.
1m
Antibodies stick the pathogens together, preventing them from reproducing or
entering the cells.
d
1m
When a pathogen enters the body, antigen on its surface stimulates the body to
34
e
produce antibodies.
1m
The antibodies produced are specific to the antigen.
1m
The level of antibodies will increase rapidly.
1m
A high level of antibodies can kill the pathogens quickly before they reproduce and
attack body cells.
1m
The skin covers the whole body.
1m
27.
a
Its outermost layer of dead cells acts as a physical barrier to pathogens. / It secretes
b
sebum which is a natural antiseptic that kills pathogens.
1m
The infected area becomes red, hot, swollen and painful.
1m
Arterioles in the infected area dilate
1m
and capillaries there increase their permeability.
1m
More blood flows to that area.
1m
More phagocytes come out of the capillaries to engulf and kill the pathogens.
1m
c
Through the respiratory tract / digestive tract / eyes / reproductive tract (any 3)
1m x 3
28.
a
Antigen in the vaccine stimulates the body to develop a primary response. 1m
B cells multiply and differentiate into plasma cells.
1m
Plasma cells produce antibodies.
1m
b
The immune response in X is faster / is stronger / lasts longer. (any 2)
1m x 2
c
i
There are fewer people infected with / died from the diseases. /
This can prevent the spread of the diseases through the community / eliminate
the diseases. /
ii
It is cheaper to prevent than to treat the diseases. (any 2)
1m x 2
This eliminates the freedom to choose.
1m
Some people may have side effects after injecting the vaccines.
1m
29.
a
b
Physical barriers: eyelash, eyelid;
1m
Chemical barrier: tears
1m
i
Cells in the epithelium of the respiratory tract are closely packed to form a
physical barriers against the entry of pathogens into the blood and other
tissues.
1m
35
Mucus lining the respiratory tract traps the invading pathogens.
1m
Cilia lining the respiratory tract move the trapped pathogens to the pharynx
where they are swallowed or coughed out.
ii
c
1m
Saliva contains lysozyme which break down the cell walls of bacteria. 1m
It is red because the blood flow to this area increases due to dilation of arterioles.
1m
It is hot because more heat is lost due to increased blood flow to the skin surface /
metabolism of this inflamed area is increased. (any 1)
1m
It is swollen due to accumulation of tissue fluid.
1m
d
They are non-specific defence mechanisms.
1m
a
When the cold virus first entered his body, it stimulated a primary response. 1m
30.
Memory cells which recognize the antigen of cold virus were produced.
1m
When the virus entered the body for the second time, a large amount of antibodies
b
were produced in a much shorter time.
1m
The virus was killed quickly before the disease developed.
1m
He may be invaded by other types of cold viruses with different antigens.
1m
The body will not develop a secondary response because the immune system is not
exposed to the antigens before.
c
1m
Cells in the epithelium of the respiratory tract are closely packed to form a physical
barrier against the entry of pathogens.
1m
Cells in the epithelium of the respiratory tract can produce mucus which traps the
pathogens.
1m
Pathogens trapped by mucus are then moved up from the bronchi to the pharynx by
the beating action of cilia. The pathogens are swallowed or coughed out.
1m
Gastric juice contains hydrochloric acid which can kill most pathogens.
1m
31.
a
Dead hepatitis B viruses / live but weakened hepatitis B viruses / surface antigens or
proteins of hepatitis B viruses
b
1m
The vaccines contain antigens which stimulate the body to produce a primary
response after injection.
1m
Memory cells that remember the type of antigens are produced in the process.
1m
36
If the body is later invaded by hepatitis B viruses, the body will develop a secondary
response.
1m
A large amount of specific antibodies and killer T cells will be produced in a short
c
d
time to destroy the viruses.
1m
The immunity is weakened when people are ill.
1m
Pathogens in the vaccines may cause disease.
1m
Wear gloves when handling wounds. /
Cover any wound with a dressing. /
Screen the blood used in blood transfusion. /
Never share injection needles. /
Stay with one sex partner. /
Always use a condom correctly during sexual intercourse.
(any 2 or other reasonable answers)
1m x 2
32.
antibody level in blood
a
primary
response
secondary
response
time
first attack
by pathogen
second attack
by pathogen
Correct shape: longer latent period and a smaller amount of antibodies produced in
b
the primary response
1m
Correct labelling of periods of primary and secondary responses
1m
When the body is first attacked by the pathogens, antigen on the surface of
pathogens stimulates the production of antibodies.
1m
Memory cells are produced to remember the type of antigen during primary
response.
1m
When the same antigen enters the body again, memory cells quickly multiply and
differentiate into plasma cells.
1m
37
The larger number of plasma cells produces much more antibodies in a much shorter
time in the secondary response.
c
1m
Antigen in the vaccine stimulates the body to produce a primary response. 1m
If the body is later invaded by the same antigen, the body will develop a secondary
response.
1m
A large amount of specific antibodies and killer T cells are produced in a shorter time
d
to destroy the pathogen.
1m
Injection of antibodies into the body.
1m
33.
Antigens stimulate immune responses.
1m
Antibodies are produced in response to specific antigens.
1m
Antibodies are made by plasma cells.
1m
Helper T cells and antigens activate B cells.
1m
B cells clone into plasma cells and memory cells.
1m
Plasma cells produce specific antibodies to antigens.
1m
Memory cells remain to give a long-term immunity.
1m
Memory cells give a faster and stronger response later.
1m
Advantages: (any 4)
1m x 4
34.
Vaccination can completely eliminate diseases from the community.
Vaccination can reduce suffering / the cost of treatment.
Vaccination can lower the death rate / reduce the number of people with disabilities due to
diseases.
Vaccination can enhance the immunity of the public against diseases.
Vaccination can prevent the outbreak of epidemics.
Disadvantages:
Each vaccine is specific for a few types of diseases only.
1m
The immunity may not be life-long.
1m
Some people may infect diseases from the vaccine.
1m
Vaccination may cause side effects or allergic reactions.
1m
Effective communication
3m
38
35.
Vaccines contain weakened pathogens, killed pathogens, viral proteins or inactivated
bacterial toxins.
1m
Antigen of the pathogen in the vaccine stimulates a primary response.
1m
Lymphocytes (B cells and T cells) are activated.
1m
They multiply and differentiate into a clone of cells.
1m
Memory cells which are responsible for the secondary response are produced.
1m
The secondary response is faster, stronger and lasts longer, thus more effective in
killing the invading pathogens.
1m
Effective communication
3m
Some pathogens in vaccines can cause diseases.
1m
Some vaccines may cause side effects or allergic reactions.
1m
36.
Some people are not suitable to have an injection, e.g. people infected with HIV. 1m
The vaccines are effective only if the mutation rate of the viruses is low.
1m
The cost of development is high as new vaccine is needed each year.
1m
It is difficult to persuade healthy people to inject.
1m
It is difficult to predict which strains of influenza viruses are to be vaccinated against.
1m
Effective communication
3m
37.
Similarities:
Both responses show a latent period.
1m
Both responses cause an increase of antibody level in the blood.
1m
The antibody level in the blood decreases after both responses.
1m
Differences:
Secondary response shows a shorter latent period.
1m
Secondary response shows a higher antibody level in the blood.
1m
After recovery, secondary response maintains a higher antibody level in the blood for a
longer time.
1m
Effective communication
3m
39