MCB 100 FINAL EXAM QUESTIONS AND ACCURATE
ANSWERS
When microbial control methods are used, microbes are destroyed at a constant rate;
there is no instantaneous death of all the microbes present. This microbial death rate is
influenced by all of the following factors, except:
A. The microbial physiological characteristics
B. The number of microbes present
C. The length of time of exposure to the treatment
D. The toxins and metabolites produced by the bacteria
E. The stability of the proteins in the bacteria - Answers - D
Determine which of the following statements is true of false and then select the correct
answer sequence:
-The term antimicrobial agent includes antibiotics, fungicidal and anti-parasitic agents
-bacteriostatic agents inhibit bacterial growth, but do not specifically kill the organisms
against which they are directed
-Agents that inhibit bacterial cell wall synthesis can be bactericidal
-Antiseptics are sufficiently nontoxic that they can be applied to skin
A. F,T,T,T
B. T,T,T,F
C. T,T,T,T
D. T,T,F,T
E. F,F,F,F - Answers - C
Moist heat kills microbes faster than dry heat because
A. water has a higher heat capacity than air, which means it takes more energy to raise
the temperature of water
B. hot water makes the cells swell and burst, while hot air just shrinks the cells
C. hot air removes the water from the cells but does not kill them right away
D. moist heat kills microbes by denaturing protein and nucleic acid structures and
disrupting cell membranes, which takes less time to kill cells than removing water by dry
heat and killing cells through oxidative reactions
E. hot air causes the cells to release water which evaporates and cools them off and
keeps them alive longer - Answers - D
Which of the following statements about pasteurization is not true?
A. Pasteurization reduces the microbial load in heat-sensitive liquids
B. Pasteurization controls microbes that cause spoilage, such as E. coli and Salmonella
sp
C. Pasteurization is a method of sterilization that kills microbes present in food
D. Pasteurization increases the shelf life of perishable liquids
E. Pasteurization involves flash heating to 135°C for about a minute - Answers - C
, An autoclave is able to achieve temperatures higher than that of boiling water
___________.
A. by decreasing the volume of liquid
B. by increasing the temperature higher than boiling water
C. by increasing the time of exposure to boiling water
D. by increasing the pressure
E. Autoclaves cannot reach temperatures higher than boiling water - Answers - D
A particular sterilization process takes 60 minutes to kill all organisms in a sample with
10^6 microbes. How long does it take to eliminate 90% of the organisms using this
process?
A. 5 minutes
B. 10 minutes
C. 30 minutes
D. 54 minutes
E. 120 minutes - Answers - B
Oxidizing agents such as chlorine or hydrogen peroxide are particularly effective against
_______ organisms. A. Microaerophilic
B. Aerobic
C. Facultative aerobic
D. Anaerobic
E. Thermotolerant - Answers - D
Contaminated hospital equipment represents a difficult environment to control against
harmful microbial growth. Which of the following statements regarding influences that
affect disinfection of hospital equipment is an accurate statement?
A. The presence of organic matter, such as dried blood or protein, will not affect the
action of antimicrobial agents.
B. The cell walls of many Gram-negative bacteria are especially resistant to many
chemicals that are used to destroy microbes.
C. Biofilms, often found contaminating hospital equipment, are relatively simple targets
for microbicides to reach effectively.
D. Antimicrobial agents work best under reduced temperatures and pressures.
E. Halogens (such as chlorine) are surface-active agents that act by decreasing the
surface tension so that microbes are more easily removed. - Answers - B
Most antibiotics come from what source?
A. Fungi
B. Bacteria
C. Plants
D. Chemical synthesis
E. Algae - Answers - B
ANSWERS
When microbial control methods are used, microbes are destroyed at a constant rate;
there is no instantaneous death of all the microbes present. This microbial death rate is
influenced by all of the following factors, except:
A. The microbial physiological characteristics
B. The number of microbes present
C. The length of time of exposure to the treatment
D. The toxins and metabolites produced by the bacteria
E. The stability of the proteins in the bacteria - Answers - D
Determine which of the following statements is true of false and then select the correct
answer sequence:
-The term antimicrobial agent includes antibiotics, fungicidal and anti-parasitic agents
-bacteriostatic agents inhibit bacterial growth, but do not specifically kill the organisms
against which they are directed
-Agents that inhibit bacterial cell wall synthesis can be bactericidal
-Antiseptics are sufficiently nontoxic that they can be applied to skin
A. F,T,T,T
B. T,T,T,F
C. T,T,T,T
D. T,T,F,T
E. F,F,F,F - Answers - C
Moist heat kills microbes faster than dry heat because
A. water has a higher heat capacity than air, which means it takes more energy to raise
the temperature of water
B. hot water makes the cells swell and burst, while hot air just shrinks the cells
C. hot air removes the water from the cells but does not kill them right away
D. moist heat kills microbes by denaturing protein and nucleic acid structures and
disrupting cell membranes, which takes less time to kill cells than removing water by dry
heat and killing cells through oxidative reactions
E. hot air causes the cells to release water which evaporates and cools them off and
keeps them alive longer - Answers - D
Which of the following statements about pasteurization is not true?
A. Pasteurization reduces the microbial load in heat-sensitive liquids
B. Pasteurization controls microbes that cause spoilage, such as E. coli and Salmonella
sp
C. Pasteurization is a method of sterilization that kills microbes present in food
D. Pasteurization increases the shelf life of perishable liquids
E. Pasteurization involves flash heating to 135°C for about a minute - Answers - C
, An autoclave is able to achieve temperatures higher than that of boiling water
___________.
A. by decreasing the volume of liquid
B. by increasing the temperature higher than boiling water
C. by increasing the time of exposure to boiling water
D. by increasing the pressure
E. Autoclaves cannot reach temperatures higher than boiling water - Answers - D
A particular sterilization process takes 60 minutes to kill all organisms in a sample with
10^6 microbes. How long does it take to eliminate 90% of the organisms using this
process?
A. 5 minutes
B. 10 minutes
C. 30 minutes
D. 54 minutes
E. 120 minutes - Answers - B
Oxidizing agents such as chlorine or hydrogen peroxide are particularly effective against
_______ organisms. A. Microaerophilic
B. Aerobic
C. Facultative aerobic
D. Anaerobic
E. Thermotolerant - Answers - D
Contaminated hospital equipment represents a difficult environment to control against
harmful microbial growth. Which of the following statements regarding influences that
affect disinfection of hospital equipment is an accurate statement?
A. The presence of organic matter, such as dried blood or protein, will not affect the
action of antimicrobial agents.
B. The cell walls of many Gram-negative bacteria are especially resistant to many
chemicals that are used to destroy microbes.
C. Biofilms, often found contaminating hospital equipment, are relatively simple targets
for microbicides to reach effectively.
D. Antimicrobial agents work best under reduced temperatures and pressures.
E. Halogens (such as chlorine) are surface-active agents that act by decreasing the
surface tension so that microbes are more easily removed. - Answers - B
Most antibiotics come from what source?
A. Fungi
B. Bacteria
C. Plants
D. Chemical synthesis
E. Algae - Answers - B
