South Tuen Mun Government Secondary School
Biology Quiz 19
(A) Choose the best answer. (15 marks)
1. A culture contained 5 x 108 bacteria per cm3. When 0.1 cm3 of a serial dilution of the culture was plated and
incubated, 50 colonies grew. By how many times had the original culture been diluted before plating?
A. 105 B. 106 C. 107 D. 108
2. A bacterial culture contains 10 000 cells. If the doubling time for this bacterium is 30 minutes, how many
cells will be present after 3 hours?
A. 60 000 B. 80 000 C. 320 000 D. 640 000
Directions: The following two questions are based on the information shown in the graph below. The change in
the number of B. subtilis growing in nutrient broth culture at 30°C for 20 hours is shown in the
graph.
3. During which 4-hour period did the number of B. subtilis double in the nutrient broth culture?
A. the 4th-8th hour B. the 6th-10th hour C. the 8th-12th hour D. the 12th-16th hour
4. The percentage increase in the number of B. subtilis in the nutrient broth culture between the 0th hour and the
6th hour is
A. 33.3%. B. 75%. C. 300%. D. 400%.
5. Which of the following is not involved in the aseptic techniques that should be carried out before working
with microorganisms?
A. wear a laboratory coat to protect ourselves
B. wash our hands thoroughly with liquid soap to prevent contamination
C. open the windows to ensure good ventilation
D. clean the work surface with disinfectants to kill the microorganisms on it
6. Which of the following can be found in virus?
(i) cell membrane (ii) a protein outer coat (iii) genetic material
A. (i) only B. (ii) and (iii) only C. (ii) only D. (i) and (iii) only
7. An investigation was carried out to measure the rate of carbon dioxide production in bread dough. Carbon
dioxide production was measured by recording the change in volume of a sample of bread dough over a
50-minute period. The results are shown in the table below.
Time (minute) / 0 / 10 / 20 / 30 / 40 / 50Volume of dough (cm3) / 10 / 14 / 18 / 21 / 23 / 25
The conclusion for this investigation was
A. 0.3 cm3 of carbon dioxide was produced per minute.
B. 0.5 cm3 of carbon dioxide was produced per minute.
C. 15 cm3 of carbon dioxide was produced per minute.
D. 25 cm3 of carbon dioxide was produced per minute.
8. Which of the following correctly shows how sludge is treated by microorganisms in the digesters in sewage
treatment?
Conditions Treatment
A. aerobic decomposition of organic substances
B. aerobic decomposition of inorganic substances
C. anaerobic decomposition of organic substances
D. anaerobic decomposition of inorganic substances
9. Which of the following are the uses of microorganisms in our daily life?
(i) making antibiotics (ii) making vaccines (iii) making enzymes in the washing powder
A. (i) and (ii) only B. (ii) and (iii) only C. (i) and (iii) only D. (i), (ii) and (iii)
10. Which of the following statements about preservatives is not correct?
A. They are used to prevent microbial deterioration.
B. Some of them can be added to foods.
C. They are chemicals produced naturally from microorganisms.
D. Some of them may cause cancer.
Directions : Questions 11 and 12 refer to the diagram below which shows a digester in a farm.
11. Which of the following statements describe the advantage of using this digester in a farm?
(i) It can reduce the use of fossil fuel to produce energy.
(ii) It can help the recycling of important nutrient for the crops.
(iii) The production of energy by the biogas is quicker than that using fossil fuel.
A. (i) and (ii) only B. (ii) and (iii) only C. (i) and (iii) only D. (i), (ii) and (iii)
12. What are the major component of the biogas and the process by which the biogas is produced?
Major component Process
A. alcohol decomposition
B. methane decomposition
C. alcohol anaerobic respiration
D. methane anaerobic respiration
13. Which of the following is a correct match between the method of food preservation and the principle
involved?
Method Principle
A. canning microorganisms are inactivated due to the lack of oxygen
B. drying microorganisms are killed by removing water.
C. freezing microorganisms are inactivated by low temperatures.
D. pasteurization microorganisms are killed by prolonged heating at above 100℃.
14. Which of the following ways by which different pathogens cause damage to humans is not correct?
Pathogen How they cause damage
A. bacteria cause excessive inflammatory responses
B. fungi release toxins
C. viruses destroy the host cells directly
D. viruses release enzymes
15. The electricity supply to a refrigerator was accidentally cut off for 24 hours. Which of the following items
stored in the refrigerator, if consumed, may lead to food poisoning?
A. fresh apple B. honey C. ice cream D. soft drink
(B) Answer the following questions. (35 marks)
1. The diagrams show some steps used when growing bacteria.
(a) Explain why the wire loop is:
(i) heated in step 1. (1 mark)
(ii) cooled in step 2. (1 mark)
(b) Explain why the lid of the Petri dish is at an angle in step 4. (1 mark)
(c) Suggest why Petri dishes containing bacteria are placed in an incubator at 20°C for 48 hours.(2 marks)
2. The diagrams below show the structure of 3 different types of microorganisms. The diagrams are not drawn to scale.
(a) Name these three types of microorganisms. (3 marks)
(b) Arrange the three types of microorganisms, according to their size, from the smallest one to the largest
one. (1 mark)
(c) Describe ONE difference between the genetic materials of
(i) A and B, (2 marks)
(ii) A and C. (2 marks)
(d) Suggest why when B infects man, it sometimes enters into a latent period and does not cause any harm
to man. (3 marks)
3. Anthrax is a disease caused by infection with the bacterium Bacillus anthracis. A vaccine against
B. anthracis is available.
Production of anthrax vaccine involves culturing B. anthracis in a fermenter to produce a protein known as protective antigen (PA).
Researchers grew three strains of B. anthracis at different temperatures and recorded the concentration of PA
produced at each temperature. The results are shown in the table.
Strain / Concentration of PA produced (gram per litre)Temperature
30ºC / 35ºC / 40ºC
X / 4.70 / 4.85 / 4.70
Y / 4.40 / 4.50 / 4.60
Z / 3.75 / 5.15 / 3.50
(a) (i) Plot a bar chart to show the concentration of PA produced in gram per litre for each strain at each
temperature. (4 marks)
(ii) Use the information to identify the strain that produces the highest concentration of PA per litre of
culture. (1 mark)
(b) At which temperature is the production of PA fastest? Give a reason why the temperature can be used to
produce a higher concentration of PA. (2 marks)
(c) Production of the vaccine against B. anthracis is carried out using batch culture.
(i) The first step in this process is to produce a starter culture. A small volume of nutrient broth is
inoculated with B. anthracis and incubated for 24 hours at 37°C. Explain why the starter culture is
incubated for 24 hours. (1 mark)
(ii) The second step in the batch process is the transfer of the starter culture to a large culture tank
containing nutrient broth. This is incubated for 27 hours at 37°C. Explain why the incubation time
and temperature must be carefully controlled during each batch culture. (1 mark)
(iii) The final volume of vaccine produced is 550 cm3. If the yield of antigen is 5 mg per cm3 of vaccine,
how much antigen is produced in total? (1 mark)
4. (a) The diagram below shows an experiment carried out by a student.
State two reasons to explain why no microorganisms grew in the flask. (2 marks)
(b) Another student carried out an investigation into the effect of different conditions on the decay of food.
The diagram below shows the set-ups.
The set-ups were observed two days later. Microorganisms grew in set-up X but not in set-ups Y and Z.
(i) Explain the results of this investigation. (4 marks)
(ii) Suggest one sign of microbial growth that can be observed in set-up X. (1 mark)
(iii) If the student drank the water in set-up X, he / she became sick. When he / she went to see a doctor,
the doctor said that he / she suffered from food-borne infection. State the meaning of food-borne
infection and its difference with food poisoning. (2 marks)
South Tuen Mun Government Secondary School
Biology Quiz 19
Marking Scheme
(A) Choose the best answer. (15 marks)
1. B 2. D 3. B 4. C 5. C
6. B 7. A 8. C 9. D 10. C
11. A 12. B 13. C 14. D 15. C
(B) Answer the following questions. (35 marks)
*spelling must be correct
1. (a) (i) The loop is heated to kill the bacteria on it. (1)
(ii) The loop is cooled so that the bacteria in the broth / tube would not be killed by high temperature. (1)
(b ) To reduce the chance of contamination by microorganisms in air / to prevent the bacteria in the air from
entering the Petri dish. (1)
(c) To allow the growth of bacteria (1) into colonies so that bacterial growth can be seen (1)
2. (a) A – *bacteria (1) B – *virus (1) C – *fungus (1)
(b) virus, bacteria, fungus OR B, A and C (1)
(c) (i) The genetic material of A is made up of DNA (1) while that of B can be made up of DNA or RNA. (1)
OR A has plasmid (1) which is a small circular extrachromosomal DNA (1) while B has not.
(ii) A has plasmid (1) which is a small circular extrachromosomal DNA (1) while C has not OR DNA of
A is circular (1) while that of C is linear (1). OR DNA of A is located free in the cytoplasm (1) while
that of C is enclosed by a layer of nuclear membrane (1).
(d) This is because DNA / genetic material of B is integrated into the DNA of the host cell (1), it replicates
along with the host DNA (1) and its genes are not expressed to lyse / kill the host cell. (1)
3. (a) (i) Title (½) – The production of protective antigen (PA) by strains A, B, C at different temperatures
Correct choice of axis (½)
Correct labels of axis : X axis – temperature (½);
Y axis – concentration of PA (gram per litre) (½)
Correct bar for strains X, Y and Z at different temperatures (½ x 3)
Label of various bar for X, Y, Z / key given (½)
(ii) Strain Z (1)
(b) 35℃ (1) because it is the optimum temperature of enzymes (1).
(c) (i) To activate the bacteria and allow the bacteria to grow to a sufficient number of cells for further
production of PA. (1)
(ii) To ensure the yield of PA in each batch culture is more or less the same. (1)
(iii) 5 x 550 = 2750 mg (1)
4. (a) Boiling kills the microorganisms in the nutrient broth. (1) The curving neck of the flask prevents the
entry of microorganisms from the air. (1)
(b) (i) In set-up Y, the concentrated sugar solution has a lower water potential as compared with the
microorganisms / food. There is a net movement of water out of the microorganisms / food by
osmosis. (1) In the absence of water / drying, microorganisms cannot grow.
In set-up Z, the temperature is lower (1), the enzyme becomes inactive / the metabolic rate is
slow. (1) Thus microorganisms cannot grow.
(ii) You can see the distilled water becomes cloudy / you can detect a bad smell / you can see moulds
growing in the distilled water and / or on the food sample. (1)
(iii) Food-borne infection means that the sickness is caused by the growth of pathogens in our body
after the intake of dirty / contaminated food. (1) It is different from food poisoning because food
poisoning is caused by the intake of toxins produced by microorganisms. (1)
8