SELECT THE MOST CORRECT ANSWER

Note that your final exam will be on vUWS. It will consist of MCQ and
short answer questions. The number of questions and value of
questions will be different to this sample exam.

Questions 1-35 are worth 1 mark each
SELECT THE MOST CORRECT ANSWER FOR EACH QUESTION
1. Which of the following statements is true?
a. viruses cannot reproduce outside of a host cell
b. bacteria cannot move
c. fungi are plants
d. algae are parasites
2. A multicellular organism that has chitin cell walls and absorbs organic material is
a(n)
a. alga
b. bacterium
c. fungus
d. virus
3. The cell wall is found in which eukaryotes?
a. fungi
b. algae
c. protozoa
d. a and b
4. You are looking at a white cottony growth on a culture medium. Microscopic
examination reveals it is multicellular. You can conclude all of the following about
this microorganism
except that it
a. has cell walls
b. has DNA enclosed in a nucleus
c. is a bacterium
d. absorbs organic nutrients
5. Which of the following lack a nucleus?
a. bacteria
b. fungi
c. protista
d. none of the above
6. The concept stating that microorganisms are the causes of infectious disease is
known as the
a. theory of evolution
b. germ theory of disease
c. cell theory of biology
d. theory of spontaneous generation
7. By definition, organisms in the same ________ are more closely related than are
those in the same ___________ .
a. genus, family
b. genus, species
c. family, genus
d. domain, kingdom
8. You are observing a cell through a microscope and note that it has no apparent
nucleus. You conclude that it most likely
a. has a peptidoglycan cell wall
b. has a cellulose cell wall
c. moves by pseudopodia
d. is part of a multicellular animal
9. The substance peptidoglycan is found in the
a. ribosomes of eukaryotes
b. cell wall of bacteria
c. chromosomes of eukaryotes
d. cell membrane of bacteria

10. Lipopolysaccharide (LPS), which is found in the outer membrane of Gramnegative
bacteria, is also known as
a. teichoic acid
b. exotoxin
c. endotoxin
d. murein
11. Which of the following is
not a characteristic of the plasma membrane?
a. maintains cell shape
b. composed of a phospholipid bilayer
c. contains proteins
d. selectively permeable
12. Which of the following statements is
true?
a. endospores are for reproduction
b. endospores allow a cell to survive environment changes
c. endospores are easily stained in a Gram stain
d. a cell can produce many endospores
13. Which of the following terms best describes a bundle of flagella at one end of a
bacterial cell?
a. peritrichous flagella
b. amphitrichous flagella
c. lophotrichous flagella
d. monotrichous flagella
14. Which of the following pairs is
not correctly matched?
a. lipid inclusions – energy reserve
b. ribosomes – protein storage
c. sulphur granules – energy reserve
d. gas vacuoles – flotation
15. Why are endospores of great practical importance in industrial and medical
microbiology?
a. because they are resistant to harsh environments and thus increase the survival of
sporeforming bacteria as compared to that of bacteria that do not form spores
b. because many endospore-formers are dangerous pathogens
c. both a and b are correct
d. neither a nor b are correct
16. If a bacterium is present in large numbers in the human gut, what are its likely
oxygen requirements? Select the most appropriate answer.
a. Aerobe or facultative anaerobe
b. Strict aerobe
c. Strict anaerobe
d. Anaerobe or facultative anaerobe
17. A culture medium on which only salt tolerant Gram-positive organisms grow and
the colonies are a mixture of pink and yellow is called a(n):
a. Selective medium
b. Differential medium
c. Enriched medium
d. a and b
e. b and c
18. Salts and sugars work to preserve foods by creating
a. depletion of nutrients
b. hypotonic environment
c. hypertonic environment

d. lower pH
19. An organic nutrient essential to an organism’s metabolism that cannot be
synthesized itself is termed a/an
a. trace element
b. micronutrient
c. growth factor
d. essential nutrient
20. Bacteria that are pathogenic in the body grow at temperatures
a. over 60°C
b. at mesophilic temperatures
c. at the same temperature as viruses
d. at thermophilic temperatures
21. Which group of microorganisms is most likely to spoil a jar of jam?
a. bacteria
b. fungi
c. protists
d. all are equally likely
22. A differential medium is one on which
a. fungi and viruses grow differently
b. two different bacteria can be distinguished
c. growth of some bacteria is suppressed
d. two different temperatures are utilised in the incubation period
23. During which growth phase will Gram-positive bacteria be most sensitive to
penicillin?
a. lag phase
b. log phase
c. stationary phase
d. equally sensitive in all phases
24. Which of the following is
not true about viruses?
a. Most viruses are visible in the light microscope
b. Viruses contain DNA or RNA but never both
c. Viruses contain a protein coat
d. Viruses depend on the host cell for the energy needed for replication
25. In order for viruses to replicate in their host cells, all of the following must occur
except
a. The viral nucleic acid must be released into the host cell
b. ATP must be synthesised by the virus
c. The virus must attach to the correct host cell
d. The host cell must be able to synthesise proteins
26. An envelope is acquired by certain viruses when
a. they enter host cells
b. the virus is assembled inside the host cell
c. they bud through the host cell membrane
d. the virus is uncoated
27. Which of the following is best to sterilise heat-sensitive solutions?
a. Dry heat
b. Autoclave
c. Gamma-irradiation
d. Pasteurisation

28. Which of the following substances can sterilise?
a. Alcohol
b. Phenolics
c. Ethylene oxide
d. Chlorine
29. Which of the following is a limitation of gamma-irradiation?
a. It can inactivate viruses
b. It can inactivate endospores
c. Radioactive waste is produced
d. Some substances are damaged by moisture
30. In boiling water, non-spore-forming bacteria die within
a. One hour
b. One-two minutes
c. Two hours
d. Three hours
31. Which will require a longer time to kill?
a. A large population of microorganisms
b. A small population of microorganisms
c. Killing time is independent of microbial numbers
d. There is no way to predict which will take a longer time to kill
32. A mycelium is:
a. a type of reproductive spore
b. the structure of the fungal cell wall
c. a mass of branching filaments
d. important for motility
33. Which of the following types of spores are asexual spores?
a. Conidiospores
b. Basidiospores
c. Ascospores
d. Zygospores
34. The contractile vacuoles of protozoa are used for
a. Storing nutrients
b. Maintaining optimal levels of water in the cell
c. Production of toxins
d. Motility
35. The formation of a cyst enables a protist to
a. move
b. synthesise protein
c. survive in the external environment
d. increase rapidly in number

The value of each question is marked on the paper
Question 36
(3 marks)
a. Describe three ways in which the structure of Gram-positive and Gram-negative cells differs.
1. ________________________________________________________________
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2. ________________________________________________________________
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3. ________________________________________________________________
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b. Explain why: (2 marks)
i. alcohol decolourises Gram-negative, but not Gram-positive, cells when performing a Gram stain.
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ii. Gram-positive cells are sensitive to penicillin, but not Gram-negative cells.
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Question 37
Match the following terms with the definitions.
(2 marks)

Term Definition

___ Halophile
___ Psychrotroph
___ Osmophile
___ Psychrophile
a. Grows at temperatures below 15C but grows optimally at >20C
b. Grows optimally at a temperature below 15
C
d. Grows optimally in the presence of high salt concentrations
e. Grows optimally in media high in salt or sugar

Question 38 (4 marks)
Distinguish between the following terms.
a. Scanning electron microscopy and transmission electron microscopy
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b. Pasteurisation and sterilisation
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Question 39 (3 marks)
Match the following terms with the examples. Each example may be used more than once, or not at all.
Term
___ Macronutrient
___ Growth factor
___ Complex medium
___ Selective medium
___ Differential medium
___ Enriched medium
Example
a. Mannitol salt agar
b. Malt extract agar
c. Blood agar
d. Nitrogen
e. Vitamin B
12
f. Manganese

Question 40
a. Fungi reproduce both sexually and asexually. Identify two major differences between these two types of

reproduction. (2 marks)
i. ________________________________________________________________
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ii.

b. The diagram shows the life cycle of a filamentous fungus. Use the information in the diagram to answer the
questions below.

i. Mark on the diagram which stages/cell types are haploid (n), which are diploid (2n) and
which are (n+n).
Describe the difference between plasmogamy and karyogamy
(1 mark)
(2 marks)
ii.

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Question 41
a. Many antibiotics target the bacterial cell wall. Name 1 such antibiotic and explain its mode of action.
(2 marks)
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b. Selective toxicity is a desirable characteristic of an antibiotic. What does ‘selective toxicity’ mean?
(1 mark)
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c. Explain why antibiotics that target the cell wall have better selective toxicity (a higher therapeutic index)
than antibiotics that target the cell membrane. (1 mark)
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Question 42 (3 marks)
a. Compare the methods by which viruses and bacteria are cultivated in the laboratory.
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b. Compare the methods by which viruses and bacteria are visualised by a microscope.
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Question 43 (3 marks)
What is the function of a flagellum?
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Question 44
a. Draw a typical growth curve of a thermophilic bacterium growing in a batch culture at:
i. 55
C
ii. 20
C (2 marks)
b. Generation time is the amount of time it takes for a population of cells to double. Using the graph below,
what is the approximate generation time of this organism? (2 marks)
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Question 45
Decimal reduction time (D value) is often used to compare the heat sensitivity of bacteria.
(3 marks)
i. Explain what the term D value means.
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ii. If the D value at 65
C for Bacterium A is 15 minutes and for Bacterium B 3 minutes, what conclusion can
you draw about the relative heat sensitivity of the two bacteria (ie which bacterium is more sensitive to heat?).
Explain your choice. ________________________________________________________________
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iii. If the D values for Bacterium A and B were measured at 90
C, would you expect the values to be higher or
lower than the D values for the same bacteria at 65
C?
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Question 46
a. Name two enzymes that are produced by bacteria that grow aerobically but not by obligate anaerobes.
(1 mark)
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b. Explain how these enzymes enable bacteria to survive in the presence of oxygen.
(3 marks)
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Question 47
Describe the differences between vegetative cells and bacterial endospores. (2 marks)
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Question 48
Manuka honey has been used as an antiseptic treatment for hundreds of years. In recent years there has
been renewed interest in the use of manuka honey to treat antibiotic resistant strains of bacteria.
a. Name and briefly describe the experiment performed to analyse the combined effect of manuka honey and
rifampicin (2 marks)
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Question 49
Describe an experiment that could be performed to visualise the interaction of different bacterial species in a
dental biofilm. Explain how a fluorescent microscope could be used with 16 S rRNA probes.
(2 marks)
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Question 50
a. Define the terms psychrotroph and psychrophile. (2 marks)
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b. Briefly describe an experiment that you could perform to determine whether a bacterium that you have
recently isolated is a psychrotroph or psychrophile. (2 marks)
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c. Explain how the results of your experiment would enable you to determine whether your bacterium is a
psychrotroph or psychrophile.. (2 marks)
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Question 51. Draw a figure comparing the lytic cycle and lysogeny in bacteriophage replication with
mammalian virus replication. (10
marks)

Question 52. Give an example of a method used to determine viable cell counts and one method used to
determine total cell counts.
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Question 53. Draw a diagram summarising the process of binary fission.
Question 54. Identify one control process that is capable of destroying endospores.
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END OF EXAM PAPER