Download public exam_body defence mechanisms

ECF Saint Too Canaan College
Biology public exam exercise
Body defence mechanisms
Name: ___________________
Class: ______ (
)
Date: _____________________
CE 2001_I_Q.3(b)(iv)
1.
Lymph node may become enlarged when a person has a sore throat. Explain why sore throat is
enlarged.
(2 marks)
CE 2004_I_Q.1(c)(iii)(iv)
2. (a) One method to confirm whether a patient is infected with the SARS virus is to test for the
presence of antibodies against this virus in the patient’s blood. Explain why these antibodies
will be produced by a SARS patient.
(2 marks)
(b) Suggest a method that can help the body develop immunity against SARS. Explain how the
immunity is developed.
(4 marks)
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CE 2003_I_Q.4(c)(i)(ii)
3.
Cholera is a human disease caused by a type of bacteria. It is transmitted through contaminated
water and food. A vaccine against this disease is made up of killed cholera bacteria. To study the
effectiveness of the vaccine, a mouse was first injected with the vaccine and then with live cholera
bacteria 20 days later. During the study, the mouse showed no sign of cholera. The changes in the
antibody level in the plasma of the mouse are shown in the graph below:
(a) Explain the rise in the antibody level between day 5 and day 7.
(2 marks)
(b) State two differences between the patterns of antibody production as induced by the two
injections. Suggest an explanation for such differences.
(5 marks)
Bio_public exam_body defence mechanisms
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AL 1999_II_Q.3(b)
4.
State and explain three features of the human body which are in the first line of defence in
preventing the entry of infectious agents.
(6 marks)
AL 2002_II_Q.1(c)
5.
If this bacterium is pathogenic to human beings, describe how we can make use of molecules
extracted from structure B to protect us from the infection of this bacterium.
(5 marks)
AL 2003_II_Q.1(e)
6.
On the surface of cells, glycoproteins are found. They are unique to each individual organism and
can act as antigens to other individuals. In humans, why is the ability to recognize and respond to
foreign antigens a merit to survival. Briefly describe one such response.
(3 marks)
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DSE 2013_IB_Q.9
7. (a) The following graph shows the change in levels of antibodies in children’s bodies:
(A) antibodies from mother
(B) children’s own antibodies with vaccination
(C) children’s own antibodies without vaccination
(i)
State the types of immunity resulting from A, B and C.
(3 marks)
(ii)
Suggest two possible ways that newborns can acquire antibodies from their mother.
A:
B:
C:
(2 marks)
(b) Explain why children who have been vaccinated against diseases are better protected than
those who have not.
(4 marks)
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ECF Saint Too Canaan College
Biology public exam exercise – Body defence mechanisms answer
1.
The pathogen that causes sore throat
stimulates the production of lymphocytes / white blood cells in structure Z.
Thus structure Z becomes enlarged.
1
1
(2)
2.
(a)
The antigen of the SARS virus
stimulates the white blood cells of the patient to produce the specific antibodies.
1
1
(b)
Injection of the weakened virus / the antigen into the body.
This will stimulate the white blood cells to develop memory for the antigen.
1
1
When the same virus enters the body,
a large amount of antibodies can be produced rapidly to kill the virus.
1
(6)
3.
(a)
The antigen in the cholera vaccine
stimulates specific white blood cells to produce antibody
resulting in the rise in antibody level.
(b)
For the second injection, the rise in antibody level occurs earlier
1
1
the rise in antibody level is faster
any two
1, 1
and the peak of the antibody level in higher
This is because as a result of the first injection, certain white blood cells will develop 1
a memory for the antigen.
When the same antigen enters the body in the second injection,
1
the white blood cells will produce a large amount of antibodies within a short time.
1
(7)
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4.
Any three of the following:
 dead cells of epidermis of intact skin (1) provide physical barrier (1)
2

2




secretions from sebaceous gland (1) contain substances that inhibit growth of
microbes (1)
mucus in respiratory tract (1) traps and stops pathogen from entering the body (1)
cilia in the respiratory tract (1) sweeps pathogen out of body (1)
gastric / digestive juice in stomach (1) is strongly acidic which kills ingested
pathogen (1)
hair at nasal passage (1) acts as filter to trap air-borne pathogen (1)
(accept other correct alternatives)
2
(2)
(2)
(2)
(6)
5.


The extracted molecules can be used as an antigen / vaccine. (1)
When this antigen is injected into the human body, they will induce the immune
system to produce memory cells. (1)

Should future infection by this bacterium occur, the memory cells can recognize the
antigen. (1)
Memory cells will trigger a series of events which rapidly produce a lot of specific
antibodies (1), and can stimulate the proliferation of killer T cells (1).
These antibodies and killer T cells can combat the infecting bacterium which bears
the same antigen. (1)


5
(5)
6.
 trigger immune response to combat / kill foreign antigens (1)
Response (anyone set, 2 marks)
 stimulate B cells (1) to produce antibody (1)
 stimulate B cells (1) to produce memory cells (1)
 stimulate T cells (1) to form killer cells (1)
 stimulate T cells (1) to release chemicals to activate phagocytes (1)
1
2
(3)
7.
(a)
(i)
(ii)
A: passive immunity (1)
B: active immunity (1)
C: active immunity (1)


some antibodies in the maternal blood pass through the placenta and enter
into the foetal blood (1)
some maternal antibodies in the mother’s milk pass to the new born via
breast feeding (1)
(3)
(2)
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7.
(b)


vaccine contains antigens (1)
which stimulate the immune system to produce memory cells for that particular
antigens (1)
 on the second exposure to the same antigen (1)

these memory cells are capable of producing a large amount of antibodies (1)
therefore, child with vaccination has a better protection
(4)
(9)
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P.7