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Chapter 24
1.
Why are antibiotics effective against bacteria but not viruses?
A
B
C
D
Viruses can hide inside host cells.
Bacteria are recognized as pathogens but viruses are not.
The enzymes of bacteria can be inhibited by antibiotics.
Viruses are resistant to antibiotics.
The graph below shows the number of reported cases of tetanus in relation to
age.
number of reported cases
2.
Infectious diseases
age group (year)
What is the percentage of total reported cases which occurred in adults aged 40
or over?
A
C
3.
4
40
B
D
8
80
A person is suffering from an illness and the doctor prescribes an antibiotic to
treat the disease. What is the patient likely to suffer from?
A
B
C
D
a viral infection
a prokaryotic infection
a eukaryotic infection
the flu (influenza)
1
4.
Viruses have a non-cellular structure. What components make up their structure?
A
B
C
D
lipid bilayer surrounding cytoplasm
lipid bilayer surrounding DNA or RNA
protein coat surrounding DNA or RNA
protein coat surrounding active mitochondria
Directions: Questions (5) and (6) refer to the bar chart below, whichshows the number
of patients suffering from four different diseases in a clinic.
45
number of patients
40
35
30
25
20
15
10
5
0
influenza
asthma
cholera dengue fever
disease
5.
Which of the above diseases is not an infectious disease?
A
C
6.
influenza
cholera
B
D
asthma
dengue fever
Which of the following matchings of the diseases and the pathogens causing
them is correct?
A
B
Disease
influenza
asthma
Pathogen
protist
fungus
C
D
cholera
dengue fever
bacterium
mosquito
2
Directions: Questions (7) to (9) refer to the photomicrographs below, which show
three types of pathogens that cause diseases in humans.
P
7.
9.
R
What are pathogens P, Q and R?
A
B
C
D
8.
Q
P
virus
bacterium
fungus
fungus
Q
fungus
virus
virus
bacterium
R
bacterium
fungus
bacterium
virus
What diseases are caused by pathogens P, Q and R respectively?
A
P
athlete’s foot
Q
influenza
R
tuberculosis
B
C
D
athlete’s foot
influenza
tuberculosis
tuberculosis
athlete’s foot
influenza
influenza
tuberculosis
athlete’s foot
Which of the following diseases is not caused by the three types of pathogens
shown above?
A
measles
B
cholera
C
AIDS
D
malaria
3
Directions: Questions (10) and (11) refer to the paragraph below.
In 1928, a Scottish scientist Alexander Fleming accidentally found that the
fungus Penicillium stopped the growth of bacteria on the same culture plate.
Penicillin, a chemical produced by Penicillium, was identified by other
scientists later. Penicillin can inhibit the formation of bacterial cell walls. Thus
the bacteria burst when they divide.
10. Penicillin is
A
an antibiotic.
B
a sulpha drug.
C
an enzyme.
D
a fungus.
11. Penicillin cannot be used to treat viral diseases because
A
viruses have no cell wall.
B
viruses cannot multiply.
C
viruses are much smaller in size than bacteria.
D
the genetic material of viruses changes rapidly.
Directions: Questions (12) to (15) refer to the paragraph below.
The threat of human swine flu (H1N1) could be with us until 2010, the
chief of the World Health Organization (WHO) said in December 2009.
Patients infected with human swine flu may have a fever, cough, sore
throat, runny nose, muscle pain and headache.
Human swine flu spreads between humans through coughing or sneezing,
and touching of the eyes, nose or mouth with hands contaminated with the virus.
Patients with human swine flu can be treated with Tamiflu or Relenza.
These drugs can help relieve the signs and symptoms, and help prevent serious
complications. However, the majority of patients can recover fully without
taking any drug.
4
12. Which of the following is/are the symptom(s) of human swine flu?
(1) runny nose
(2) muscle pain
(3) headache
A
C
(1) only
(2) and (3) only
B
D
(1) and (3) only
(1), (2) and (3)
13. Human swine flu is mainly transmitted by
A
C
droplets.
body fluid.
B
D
vectors.
direct contact.
14. Which of the following are the effective ways to reduce the risk of having human
swine flu?
(1) Avoid going to crowded places.
(2) Wear a surgical mask.
(3) Wash the hands with soap and water frequently.
A
C
(1) and (2) only
(2) and (3) only
B
D
(1) and (3) only
(1), (2) and (3)
15. Which of the following statements about Tamiflu and Relenza is/are correct?
(1) They are antibiotics.
(2) They can lower the risk of complications of human swine flu.
(3) They can cure human swine flu.
A
B
C
D
(2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
16. Which of the following is/are proper way(s) of using antibiotics?
(1) Use only when infected with viruses.
(2) Use only one kind of antibiotic at one time.
(3) Finish the course even after all the symptoms of the disease have
disappeared.
A
C
(1) only
(3) only
B
D
(2) only
(2) and (3) only
5
17. Besides antibiotics, which of the following can also be used to treat bacterial
infections?
A
B
C
D
vaccines
antiseptics
sulpha drugs
antibodies
18. Which of the following statements about the cocktail therapy is/are correct?
(1) It is a cure for AIDS.
(2) It includes the use of a combination of drugs.
(3) It targets different points in the reproductive process of HIV.
A
C
(1) only
(2) and (3) only
B
D
(1) and (2) only
(1), (2) and (3)
19. Indiscriminate use of antibiotics may
A
B
C
D
lead to the release of toxins by bacteria.
lead to addiction to the drugs.
cause some diseases to become untreatable.
cause widespread occurrence of viral infections.
Directions: Questions (20) and (21) refer to the diagram below, which shows the life
cycle of malaria pathogens.
Stage I
Vector becomes
infected with malaria
pathogens
Stage II
Infected vector
injects malaria
pathogens into the
blood of a human
Stage III
Malaria pathogens
reproduce in the liver
of a human
Stage VI
Vector picks up
malaria pathgens in
the blood
Stage V
Red blood cells
burst, releasing toxic
substances and
malaria pathogens
Stage IV
Malaria pathogens
invade red blood
cells of a human
6
20. Which of the following is the vector of malaria pathogens?
A
B
C
D
Plasmodium
mosquito
rat
virus
21. Which of the following stages causes a fever in the infected person?
A
B
C
D
stage II
stage III
stage IV
stage V
22. Which of the following pairs of diseases have a similar way of transmission?
A
B
C
D
AIDS and SARS
dengue fever and malaria
cholera and hepatitis B
gastroenteritis and tuberculosis
23. Which of the following diseases is not caused by viruses?
A
B
AIDS
influenza
C
D
hepatitis B
cholera
7
Short questions
1.
Outline how antibiotic resistance in bacteria can arise in response to
environmental change.
(5 marks)
2.. The graph shows the number of reported cases of hospital acquired infection
(HAI) in a hospital over a period of 7 years.
220
200
180
160
140
number of
120
reported
cases of HAI 100
80
60
40
20
0
2000
2001
2002
2003
2004
2005
2006
time (year)
a
Between which two years did the greatest decrease in total number of cases
of HAI occur?
(1 mark)
b
Using the graph, calculate the percentage increase in reported cases of HAI
between 2001 and 2002.
(1 mark)
c
In 2003 a new handwashing procedure was introduced at the hospital.
Predict the effect this procedure will have on the overall trend in cases of
HAI after 2006 and give a reason for your answer.
(1 mark)
8
The table below shows the percentage of cases of HAI in the hospital caused by
two species of bacteria over the same 7-year period.
Percentage of cases of HAI in each year (%)
3.
2000
2001
2002
2003
2004
2005
2006
Clostridium
31
30
32
30
54
57
59
Staphylococcus
34
31
33
32
31
33
33
d
Using the graph and the table, calculate the number of cases of HAI caused
by Clostridium species in 2001.
(1 mark)
e
Compare the overall trend in the percentage of Clostridium cases over the
7-year period with that of Staphylococcus cases.
(1 mark)
f
Using the graph and the table, what conclusion can be drawn about the
effectiveness of the new handwashing procedure on the number of cases of
Staphylococcus species?
(1 mark)
The diagrams below show a Petri dish before and after a fungus was added in an
experiment by Alexander Fleming.
Before
After
bacteria
bacteria
fungus
a
What effect did the fungus have on the bacteria?
(1 mark)
b
Name the substance produced by the fungus that caused this result.
(1 mark)
Choose from:
MRSA (Methicillin Resistant Staphylococcus aureus)
penicillin
c
microorganisms
Complete the following sentences.
(2 marks)
Choose from:
resistant
chemicals
Medicines called i
antibiotics
drugs
help fight diseases caused by bacteria.
However, it is important that they are not overused because bacteria
can become ii
to them.
9
4.
a
Two types of microorganisms which cause disease are bacteria and viruses.
Using a line, link each microorganism to the disease it causes.
b
One disease will not be used.
(2 marks)
Complete the following sentences.
(3 marks)
Choose from:
painkiller
antibiotic
stopped
penicillin
In 1928 Alexander Fleming was growing bacteria. After some time, he
noticed that the bacteria i
growing where some of the mould had
started to grow. A substance from the mould, later named ii
caused this to happen. This was the first iii
c
State one way that blood clotting protects the body.
to be made.
(1 mark)
10
5.
The diagram shows an observation noted by Alexander Fleming in his
laboratory.
growth of fungus
bacteria
no bacteria
bacterial culture
growing in a Petri dish
a
He decided that it was not the fungus itself, but a substance spreading from
it that stopped the bacteria growing. How does the diagram suggest this?
(1 mark)
b
It took many years from Fleming’s initial observations until the
development of the first antibiotic. Name this antibiotic and suggest two
reasons why it took many years to develop it.
6.
(3 mark)
The table below shows the ways of action of two antibiotics.
Antibiotic
Penicillin
Way of action
Inhibits the formation of the bacterial cell walls by
preventing the formation of cross-linking
Inhibits protein synthesis in bacterial cells by binding to the
Tetracycline
a
ribosomes
Explain why the two antibiotics are not effective in treating viral
infections.
(2 marks)
b
How does penicillin kill bacteria?
(1 mark)
c
Describe how antibiotic resistance develops in bacterial populations.
(4 marks)
11
7.
The use of antibiotics reduces the amount of beneficial bacteria in the intestine
that aid digestion and help keep the amount of harmful bacteria (e.g Clostridium
difficile) under control. The elderly and people staying in hospitals are most
likely to be infected with Clostridium difficile.
a
Suggest why the eldery and people staying in hospitals are most likely to be
infected with Clostridium difficile.
b
(2 marks)
The graph below shows the number of patients infected with
Methicillin Resistant Staphylococcus aureus (MRSA) and Clostridium
difficile from 2005 to 2009 in a country.
3000
Clostridium difficile
number of patients
2500
2000
1500
1000
MRSA
500
0
2005
i
2006
2007
year
2008
Describe the trend of the number of patients infected with the two
bacteria from 2005 to 2009.
ii
2009
(2 marks)
The problem of infection of MRSA is highly concerned by the public.
On the other hand, less is known about the infection of Clostridium
difficile. Does the public impression of the relative problems of these
two bacteria match the real situation shown by the data? Explain.
(3 marks)
8.
a
Name two types of disease-causing pathogens.
(2 marks)
b
Give one disease caused by each pathogen stated in a.
(2 marks)
c
Name the type of pathogen that can be killed by antibiotics.
(1 mark)
12
9.
Cholera is a disease caused by the bacterium Vibrio cholerae. The outbreak of
cholera usually occurs after disasters like earthquakes and flooding.
a
b
How is cholera transmitted from person to person?
(2 marks)
Explain why outbreak of cholera usually occurs after disasters like
earthquakes and flooding.
(2 marks)
c
d
Suggest how a patient with cholera can be treated.
State one way we can do to prevent the spread of cholera.
10. a
(1 mark)
(1 mark)
Some patients are found to be infected with a ‘superbug’ called
Methicillin Resistant Staphylococcus aureus (MRSA) after surgery. MRSA
is resistant to many antibiotics.
i
ii
b
State two precautions doctors should take to avoid infecting patients
during surgery.
(2 marks)
Explain why infection of MRSA can be dangerous.
(1 mark)
Scientists carried out an investigation into the effect of a chemical on the
growth of bacteria. They added a drop of this chemical to an agar plate with
colonies of bacteria. The agar plate was then incubated at 37°C for 24
hours.
The result is shown below:
colonies of
bacteria
a drop of
chemical
before incubation
after incubation
Comment on the effectiveness of this chemical in treating bacterial
infections.
(2 marks)
13
11. Complete the following table, which shows the types of pathogens and the ways
of transmission of four different diseases.
Disease
(4 marks)
Type of pathogen
Way of transmission
Malaria
AIDS
Tuberculosis
Influenza
12. The diagram below shows an investigation carried out to study the effectiveness
of four antibiotics. Paper discs soaked with four different antibiotics (P, Q, R and
S) were put on an agar plate spread with bacteria. The agar plate was then
incubated at 30°C for 2 days. The results are shown below:
paper disc
soaked with
antibiotic
P
bacterial
lawn
S
Q
R
clear zone
a
Explain why clear zones appeared around the paper discs.
b
Based on the experimental results, evaluate which antibiotic is most
effective. Explain briefly.
c
(2 marks)
(2 marks)
Apart from the effectiveness of antibiotics, state one other feature of the
antibiotic which affects the size of the clear zone.
(1 mark)
14
13. Hens are often raised in cages within a house for their meat and eggs. To
increase income, many hens are crowded in a cage. Antibiotics are often added to
the drinking water of the hens to prevent them from having diseases. This is an
example of indiscriminate use of antibiotics.
a
Explain why hens that are crowded in cages are often infected with
pathogens.
(1 mark)
b
c
State one other example of indiscriminate use of antibiotics.
State the consequence of indiscriminate use of antibiotics.
(1 mark)
(3 marks)
14. A student suffered from a sore throat and a runny nose. He took some antibiotics
to treat the disease without seeking any medical advice from a doctor. Describe
how his action might lead to the development of antibiotic resistant bacteria.
(4 marks)
15. a
The diagrams below show two cells, X and Y. One of the cells is a human
cell while the other is a bacterial cell.
X
Y
i
Which one, X or Y, is a bacterial cell?
ii
State two differences of the cells shown in the above diagrams that
allow you to identify which cell is a bacterial cell.
b
(1 mark)
(2 marks)
Tuberculosis is a disease caused by the bacterium Mycobacterium
tuberculosis. Antibiotics can be used to treat tuberculosis.
i
What are antibiotics?
(2 marks)
ii
Explain why antibiotics are safe to humans.
(1 mark)
15
Structured questions
16. The diagram below shows the number of men and women with tuberculosis (TB)
in England and Wales between 1988 and 2005.
number of
men and
women with
tuberculosis
year
a
i
Calculate the percentage change in the number of men with
tuberculosis between 1988 and 2005. Round your answer to the nearest
whole number. Show your working.
ii
(2 marks)
Using the above diagram, describe how the number of people with
tuberculosis in England and Wales has changed between 1988 and
2005.
(3 marks)
16
b
The table below lists the results of treatments for the 1163 newly reported
cases of tuberculosis in England and Wales during 2004. The results were
collected towards the end of 2006.
Treatment
completed
777
i
Died
Still
being
treated
Treatment
stopped
Moved
away
Unknown
outcome
Total
59
47
6
24
250
1163
Using only the information in the above table, suggest why
tuberculosis is difficult to control even in economically advanced
countries such as England and Wales.
ii
(3 marks)
Treatment for tuberculosis consists of the use of a range of antibiotics.
Explain why a range of antibiotics must be used.
(2 marks)
17. The table below shows the percentage of people with HIV/AIDS in the USA and
Sub-Saharan Africa in 2005.
Region
Percentage of people with HIV/AIDS
Women
Men
Children
USA
24
75
1
Sub-Saharan Africa
54
38
8
In 2005, the estimated number of people living with HIV/AIDS in Sub-Saharan
Africa was 24 500 000.
a
i
Using the data from the table, calculate the number of children with
HIV/AIDS in Sub-Saharan Africa. Show your working.
ii
(2 marks)
Use the data in the table to describe the differences between the
population with HIV/AIDS in the USA and in Sub-Saharan Africa.
(2 marks)
iii
b
Suggest reasons for the differences described in a ii.
(2 marks)
Suggest why 24 500 000 may not have been an accurate estimate of the
number of people with HIV/AIDS in Sub-Saharan Africa in 2005.
(2 marks)
17
18. One third of the world’s population is currently infected with the bacterium that
causes tuberculosis (TB).
5 to 10% of people infected with this bacterium develop TB at some time during
their life.
a
The table below shows the number of cases of TB in 2004 in Africa and
Europe.
Region
Number of cases of TB per 100 000 population
Africa
518
Europe
65
Suggest reasons for the difference in the number of cases of TB in Africa
and Europe shown in the table.
b
(3 marks)
Strains of bacteria that cause TB have developed resistance to antibiotics.
Explain how bacteria that cause TB have developed resistance to antibiotics.
(5 marks)
19. The diagram below shows the life cycle of the malarial parasites.
mosquitoes take up
parasites when they
suck blood from an
infected person
parasites move to
the salivary gland of
the mosquitoes
in mosquito
in human
parasites reproduce
in red blood cells,
the cells finally burst
parasites reproduce
in the liver
parasites enter the blood
of a human when the
human is bitten by the
mosquitoes
a
Name the parasite that causes malaria and state which type of pathogen it
belongs to.
(2 marks)
b
c
Explain why people infected with malaria develop fever.
(1 mark)
State one other disease that has a similar way of transmission as malaria.
Explain your answer.
(2 marks)
d
Explain how each of the following actions prevents the transmission of
malaria.
i
ii
iii
Use of insect repellent spray
Draining swamps
Introduction of sterile male mosquitoes
(1 mark)
(1 mark)
(1 mark)
18
20. The table below shows some information about four diseases.
Disease
Caused by
Way of transmission
Whooping cough
Bacteria
Coughs and sneezes
Tetanus
Bacteria
Soil
Hepatitis A
Viruses
Food and water
Hepatitis B
Viruses
Body fluid
a
Which two diseases can be treated with antibiotics?
b
Give one precaution we can take to prevent the infection of tetanus. Explain
your answer.
c
(2 marks)
(2 marks)
Nurses, doctors and dentists are at risk of infecting with hepatitis B.
i
Why are they at risk of infecting with the hepatitis B virus? (1 mark)
ii
Give two ways they can protect themselves from having hepatitis B.
(2 marks)
iii
State one other disease that has a similar way of transmission as
hepatitis B.
(1 mark)
19
21. A student prepared a sterile nutrient agar plate. He flooded the agar plate with
water from a pond, sealed the plate and incubated it at 37°C for 72 hours.
a
b
i
Explain why nutrient agar was used instead of plane agar. (1 mark)
ii
Explain why the student incubated the plate at 37°C.
(1 mark)
The diagram below shows the agar plate. Two kinds of microorganisms
were found on the plate.
bacteria
fungi
i
Explain why bacteria did not grow around the fungus.
(2 marks)
ii
Explain how the discovery of the phenomenon in b i has led to the
advancement of medical technology in relation to infectious diseases.
(4 marks)
22. The diagram below shows the structure of a bacterium.
X
Y
Z
a
Name structures X, Y and Z.
(3 marks)
b
Antibiotics are chemicals that can kill or inhibit the growth of bacteria.
Describe one action of antibiotics on each of the structures X, Y and Z.
(6 marks)
20
23. PABA can be converted into a product which is essential for the growth of
bacteria by enzymes.
Sulpha drugs are a group of chemicals derived from a sulphur-containing red
dye. They are used in the treatment of bacterial infections.
The diagram below shows the chemical structure of PABA and a sulpha drug.
OH
C
NH2
PABA
OH
O
O
S
O
NH2
sulpha drug
a
Based on the molecular structure of PABA and sulpha drug shown in the
above diagram, explain how this sulpha drug can be used to treat bacterial
infections.
(5 marks)
b
Give reasons to explain why sulpha drugs cannot be used to cure influenza.
(2 marks)
c
i
Besides sulpha drugs, name one more type of chemical that can be
used in the treatment of bacterial infections.
(1 mark)
ii
State three ways in which this type of chemical inhibits the growth or
kills the bacteria.
(3 marks)
21
24. The diagram below shows the structure of a human immunodeficiency virus,
HIV.
X
Y
lipid membrane
Z
a
Name structures X, Y and Z.
b
AIDS may develop if HIV enters the bloodstream of a person.
i
State two ways in which HIV enters the bloodstream.
(2 marks)
ii Suggest two ways in which we can protect ourselves against AIDS.
(2 marks)
c
Viral diseases are difficult to treat. David Ho proposed the cocktail therapy
for treating AIDS. During the treatment, the patients need to take a
combination of drugs.
i
ii
(3 marks)
Explain why viral diseases are difficult to treat.
(2 marks)
Explain why a combination of drugs have to be used in the cocktail
therapy.
(1 mark)
25. Read the following passage and answer the questions that follow.
Tuberculosis was a major disease that caused many deaths in Europe in the
17th century. It is believed that the high population density and the poor sanitary
conditions of the cities favoured the spread of the disease.
There was no cure of the disease until the invention of antibiotics.
However, the antibiotic therapy soon became ineffective. Tuberculosis is still a
problem in many parts of the world today.
a
Explain why high population density in European cities during the 17th
century favoured the spread of tuberculosis.
b
(3 marks)
Suggest two ways in which the government can do to prevent the spread of
tuberculosis.
(2 marks)
c
Explain why the antibiotic therapy soon became ineffective.
(2 marks)
d
State one possible solution to alleviate the problem in c.
(1 mark)
22
Essays
26. Give an account on the ways of transmission of infectious diseases from one
person to another. Name two diseases transmitted by each way.
(11 marks)
27. Discuss how the impact of disease on the human population can be reduced.
(10 marks)
28. Describe the differences between viruses and bacteria as causes of infectious
diseases in humans.
(11 marks)
23
Answers
Questions No.
Key
Question No.
1.
C
31.
2.
D
32.
3.
B
33.
4.
C
34.
5.
B
35.
6.
C
36.
7.
C
37.
8.
A
38.
9.
D
39.
10.
A
40.
11.
A
41.
12.
C
42.
13.
A
43.
14.
D
44.
15.
A
45.
16.
C
46.
17.
C
47.
18.
C
48.
19.
C
49.
20.
B
50.
21.
D
51.
22.
B
52.
23.
D
53.
24.
54.
25.
55.
26.
56.
27.
57.
28.
58.
29.
59.
30.
60.
Key
24
1.
Bacteria reproduce very rapidly and their genetic material changes rapidly.
1m
An increase in exposure to antibiotics is the environmental change that selects
resistant varieties.
1m
e.g. frequent use of antibiotics in hospitals / adding of antibiotics to animal feed /
inappropriate prescriptions of antibiotics / not finishing the course of antibiotics.
1m
Bacteria without resistance die / Resistant bacteria survive and reproduce,
1m
resulting in a change in the genetic make-up of the whole population.
1m
a
2002-2003
1m
b
(216 - 180)/180 x 100% = 20%
1m
c
The number of cases will continue to decrease. This is due to the increasing
2.
uptake of the new procedure.
1m
OR
The number of cases will level off. The uptake of the new procedure has reached
a saturation point.
1m
d
180 x 30% = 54 cases
1m
e
The percentage of cases caused by Clostridium increased. The percentage of
cases caused by Staphylococcus remained level.
f
1m
The new procedure has had great effect / has reduced the number of cases. /
The new procedure was more effective against Staphylococcus than Clostridium.
1m
3.
a
The fungus destroyed bacteria / killed bacteria / stopped bacterial growth.
1m
b
penicillin
1m
c
i
antibiotics
1m
ii
resistant
1m
4.
a
b
Bacteria: salmonella (food poisoning)
1m
Viruses: flu
1m
i
stopped
1m
ii
penicillin
1m
25
iii
c
antibiotic
1m
Blood clotting stops bleeding / prevents infection / stops bacteria from entering
the body from the wound.
1m
a
The bacterial free zone extends beyond the fungus.
1m
b
The antibiotic is penicillin.
1m
5.
Reasons:
It took time to isolate / identify the active chemical. /
Tests / trials had to be carried out to check whether the chemical was effective /
safe. /
Licensing process took time. (any 2)
1m x 2
6.
a
Penicillin is not effective against viruses because viruses do not have a cell wall.
1m
Tetracycline is not effective against viruses because viruses do not contain
ribosomes. Viruses use ribosomes of the host to synthesize proteins.
b
Under the action of penicillin, bacteria cannot form cell walls. Therefore they burst
when they divide.
c
1m
1m
Due to random mutation / random change in genetic material, one of the bacteria
in the population develops antibiotic resistance.
1m
In an environment of heavy antibiotic use, the non-resistant bacteria are killed.
1m
Only the antibiotic resistant bacterium is selected to survive.
1m
The antibiotic resistant bacterium reproduces rapidly. The whole population of
bacteria become resistant to antibiotic.
1m
The immunity of the elderly may be weak.
1m
7.
a
People in hospitals are more likely to be exposed to Clostridium difficile / more
likely to be on antibiotics (thus the amount of beneficial bacteria in the intestine is
26
reduced by the antibiotics).
b
i
1m
The number of patients infected with Clostridium difficile was increasing.
1m
The number of patients infected with MRSA was more or less the same /
ii
decreased slightly.
1m
The public impression did not match the real situation.
1m
The data shows that the cases of MRSA were decreasing while the cases of
Clostridium difficile were increasing.
1m
There were fewer patients infected with MRSA.
1m
8.
a
Viruses / bacteria / protists / fungi / parasitic worms / prions (any 2)
1m x 2
b
Any two from:
1m x 2
Viruses: influenza / SARS / dengue fever / measles / common cold
Bacteria: cholera / tuberculosis
Protists: malaria
Fungi: athlete’s foot
Parasitic worm: inflammation of bile duct
Prions: Creutzfeldt-Jakob disease (CJD)
(diseases should match the pathogens stated in a)
c
Bacteria
1m
a
Cholera is transmitted by contaminated water
1m
and contaminated food.
1m
9.
b
After disasters, there is a lack of treated / clean drinking water. /
The sanitary conditions become poor after disasters. /
The sewage treatment systems broke down. (any 2)
1m x 2
c
By rehydration / by taking antibiotics
1m
d
Wash the hands before handling food. /
Cook food thoroughly. /
Keep meat, milk and egg products refrigerated below 4°C. (any 1)
1m
27
10.
a
i
Sterilize the instruments / sterilize the surroundings / sterilize the clothing /
wear gloves and a surgical mask. (any 2)
ii
1m x 2
MRSA is resistant to many antibiotics. Infected patients cannot be treated with
common antibiotics.
b
1m
There were fewer bacterial colonies on the agar plate. / The bacterial colonies
became smaller.
1m
This indicated that the chemical is effective in killing bacteria.
1m
11.
Disease
Type of pathogen
Way of transmission
Malaria
Protists
By vectors
AIDS
Viruses
By body fluids
Tuberculosis
Bacteria
By air
Influenza
Viruses
By droplets
1m for each correct row
1m x 4
12.
a
Antibiotics from the paper discs diffused into the agar
1m
and killed the bacteria in areas around the discs.
1m
R is most effective in killing these bacteria
1m
because the clear zone around it was the largest.
1m
c
Size of the antibiotic molecule
1m
a
As the hens are closely packed together, pathogens can easily spread from one hen
b
13.
to another.
1m
b
Take antibiotics unnecessarily. / Not finish the course of antibiotics.
1m
c
The development of antibiotic resistance in large populations of bacteria is speeded
up. /
Previously treatable diseases may become untreatable. /
Outbreaks of diseases may lead to heavy loss of lives. /
Development of new antibiotics will use many of the resources in the society. /
Antibiotics will kill the beneficial bacteria as well and this may encourage the growth
of pathogens. (any 3)
1m x 3
28
14.
The student took antibiotics without confirming whether the signs were caused by
bacterial infection or an infection of other pathogens.
1m
If he was infected by other pathogens instead of bacteria, he was taking antibiotics
unnecessarily.
1m
This would increase the exposure of bacteria to antibiotics, which would kill the
non-resistant bacteria.
1m
The resistant bacteria would be selected to survive and reproduce, and the whole
population of bacteria would become resistant to the antibiotics.
1m
a
1m
15.
i
Y
ii
Y has a cell wall while X does not. /
Y does not have a true nucleus while X has a true nucleus. /
Y does not have organelles like mitochondria and endoplasmic reticulum while
X has these organelles. (any 2)
b
i
ii
1m x 2
Antibiotics are chemicals produced synthetically or naturally from
microorganisms.
1m
They can kill or inhibit the growth of other microorganisms.
1m
Since the structure and metabolism of human cells and bacterial cells are
different, antibiotics do not act on human cells.
1m
(4450 - 2700)/2700 x 100%
1m
= 65%
1m
16.
a
i
ii
Both the numbers of men and women with tuberculosis have increased. /
Both lines of men and women show a marked dip at one point. /
The number of men with tuberculosis has increased slowly until 1998 / has
increased faster after 1999. /
The increase in women was more uniform. /
There were always fewer cases in women than in men. (any 3)
b
i
1m x 3
The table shows that not all the people have completed the treatment. 1m
29
The treatment takes a long time / the patients remain infectious for a long time.
1m
A number of people moved away. They may carry tuberculosis pathogens to
ii
other places.
1m
The pathogens mutate frequently / have many strains.
1m
They may become resistant if only one antibiotic is used.
1m
24 500 000 x 8%
1m
= 1 960 000
1m
17.
a
i
ii
Smaller proportion of AIDS sufferers in Sub-Saharan Africa were men. /
Larger proportion of AIDS sufferers in Sub-Saharan Africa were women. /
Larger proportion of AIDS sufferers in Sub-Saharan Africa were children.
(any 2)
iii
1m x 2
There was less homosexual transmission in Sub-Saharan Africa. /
There was more heterosexual transmission in Sub-Saharan Africa. /
There was more transmission from mother to child in Sub-Saharan Africa.
(any 2)
b
1m x 2
Some infected people may not have been diagnosed. /
Some people may have been incorrectly diagnosed. /
The number of cases may not have been reported accurately. (any 2)
1m x 2
18.
a
In Africa, people suffered from malnutrition / protein deficiency, which weakened
their immune system. / More people had AIDS which weakened the immune
system. /
Antibiotics / drugs / vaccination was / were not readily available in Africa. /
There were not enough hospitals / doctors / health clinics in Africa. /
People in Africa did not complete drug treatments. /
People in Africa did not go for diagnosis / treatment. /
b
More people in Africa were living in crowded conditions. (any 3)
1m x 3
Bacteria showed genetic variation in resistance to antibiotics
1m
as a result of mutation / a change in genetic material.
1m
In an environment with antibiotic acting as selection pressure,
1m
bacteria with a gene for resistance to antibiotic were more likely to survive. 1m
Resistant bacteria divided and the gene for resistance passed on to offspring,
30
leading to the development of antibiotic resistance in large populations of the
bacteria.
1m
Parasite: Plasmodium
1m
Type of pathogen: Protists
1m
19.
a
b
c
d
Toxic substances released from the bursting of infected red blood cells cause the
fever.
1m
Dengue fever
1m
Both of them are transmitted by mosquitoes.
1m
i
This can prevent mosquitoes from biting humans.
1m
ii
This can remove the breeding place of mosquitoes / kill the larvae of
iii
mosquitoes.
1m
This can prevent successful reproduction of mosquitoes.
1m
20.
a
Whooping cough and tetanus
1m x 2
b
Cover any wound with a dressing when working in the garden.
1m
This is to prevent tetanus bacteria from entering the body through the wounds.
1m
c
i
They are frequently in contact with the blood from patients.
ii
Wear gloves when handling wounds. /
1m
Cover any wound with a dressing. /
Receive vaccination. (any 2)
1m x 2
iii
AIDS
1m
i
Nutrient agar provided nutrients required for the growth of microorganisms.
21.
a
1m
ii
To provide an optimum temperature for the growth of microorganisms.
1m
b
i
The fungus released a chemical
1m
which inhibited the growth of bacteria.
1m
31
ii
Since the fungus can release a chemical that inhibits the growth of bacteria,
1m
this chemical, if not toxic to the human body,
1m
can be extracted and used to cure infectious diseases in humans.
1m
This is how antibiotics were discovered.
1m
22.
a
b
X: cell wall
1m
Y: cell membrane
1m
Z: nucleic acid / DNA
1m
Structure X:
Some antibiotics inhibit the formation of bacterial cell walls.
1m
The bacteria burst when they divide.
1m
Structure Y:
Some antibiotics damage the cell membranes of bacteria.
1m
The cell contents leak out and the bacteria die.
1m
Structure Z:
Some antibiotics inhibit the synthesis of nucleic acids
1m
so that bacteria cannot carry out cell division.
1m
The chemical structure of sulpha drug is similar to that of PABA.
1m
This sulpha drug is a competitive inhibitor.
1m
It competes with PABA for the active sites of enzymes in bacteria.
1m
23.
a
Therefore it slows down / inhibits the formation of the product essential for the
b
growth of bacteria.
1m
As a result, bacteria in the patient’s body cannot grow.
1m
Influenza is caused by viruses.
1m
Viruses use machinery of the hosts to replicate instead of producing growth
c
substances themselves.
1m
i
Antibiotics
1m
ii
Some antibiotics inhibit the formation of bacterial cell walls. /
Some antibiotics damage the cell membranes of bacteria. /
Some antibiotics inhibit the synthesis of nucleic acids in bacterial cells. /
Some antibiotics inhibit protein synthesis in bacterial cells. (any 3)
1m x 3
32
24.
a
b
X: surface protein
1m
Y: nucleic acid
1m
Z: protein coat
1m
i
HIV enters the bloodstream through wounds.
1m
HIV enters the bloodstream by blood transfusion.
1m
ii
Wear gloves when handling wounds. /
Cover any wound with a dressing. /
Never share injection needles. /
Stay with one sex partner. /
Always use a condom correctly during sexual intercourse. (any 2)
c
i
1m x 2
It is because many metabolic functions of viruses depend upon the cellular
machinery of the host.
1m
Thus, drugs that work against the metabolism of the viruses may also affect
ii
the metabolism of the host cells.
1m
To prevent HIV from developing drug resistance.
1m
25.
a
Tuberculosis spreads by air.
1m
High population density decreased the distance between people.
1m
Tuberculosis bacteria were transmitted from infected people to the others in a short
b
distance.
1m
Isolate people infected with tuberculosis.
1m
Maintain good hygiene of the city.
1m
(or other reasonable answers)
c
d
The bacteria developed antibiotic resistance.
1m
They were no longer killed or inhibited by antibiotics.
1m
Use antibiotics only when they are truly needed. /
Complete the course of antibiotics as advised by doctors. /
Implement effective measures to control the spread of pathogenic bacteria. /
Develop new drugs or alternative treatment. (any 1)
1m
33
26.
Any four ways of transmission with examples:
2m x 4
By droplets:
When patients talk, cough or sneeze, droplets containing pathogens are expelled from the
breathing system. Transmission of diseases occurs when these droplets deposit on the
mucous membranes of the eyes, nose or mouth of another person.
e.g. influenza / common cold / SARS (any 2)
By air:
Dust particles and droplet nuclei carrying pathogens and fungal spores in air are inhaled
into the body and cause diseases.
e.g. measles, tuberculosis
By water:
Water contaminated by patients’ faeces is drunk by another person.
e.g. cholera, gastroenteritis
By food:
Food contaminated with pathogens are eaten.
e.g. cholera, food poisoning
By body fluid:
Pathogens in the blood of patients enter the body of another person through wounds,
sharing of injection needles, blood transfusion or during childbirth. Pathogens in semen
and vaginal fluid of the patients enter the body of another person during sexual
intercourse.
e.g. AIDS, hepatitis B
By vector:
Pathogens are picked up by some organisms and transferred to another person.
e.g. malaria, dengue fever
By direct contact:
Pathogens transfer directly when patients are in contact physically with another person.
e.g. athlete’s foot, sexually transmitted diseases such as genital herpes
Effective communication
3m
34
27.
Introduce vaccination programmes, e.g. vaccines for measles / polio / whooping cough /
smallpox. /
Use insecticides / drugs / nets in the control of malaria. /
Educate the public about the prevention of diseases, e.g. use of condoms in the control of
HIV. /
Improve hygiene / sanitation. /
Ensure a supply of clean drinking water in the control of cholera. /
Add chemicals / sterilizing agents in drinking water, e.g. chlorine. /
Develop an effective sewage treatment process. /
Be careful when handling food, e.g. refrigerate meats and milk to prevent food poisoning. /
Improve the medical facilities / increase the number of hospitals / doctors. /
Work with the aid agencies around the world, e.g. WHO.
(any 8 or other reasonable answers)
1m x 8
Effective communication
2m
28.
Viruses cause diseases only inside cells while bacteria can cause diseases inside or
outside cells.
2m
All viruses entering the human body can cause diseases while many bacteria in
humans do not cause diseases.
2m
Viruses cause diseases by destroying the cell membranes of the host cells or stopping
the synthesis of nucleic acids or proteins in the host, while bacteria cause diseases by
producing toxins or enzymes.
2m
Bacterial infections can be treated by antibiotics and sulpha drugs while viral infections
cannot.
2m
Effective communication
3m
35