BACTERIAL SURVIVAL

Question 1

1. Which organisms can produce their own food from inorganic substances?
   A) Heterotrophs
   B) Autotrophs
   C) Chemolithotrophs
   D) Animals

Answer 1

B) Autotrophs
Rationale: Autotrophs are organisms that can produce their own food from the substances available in their surroundings without the need for organic nutrients.

Question 2

2. What do chemolithotrophs primarily use as their carbon source?
   A) Oxygen
   B) Methane
   C) Organic matter
   D) CO2

Answer 2

D) CO2
Rationale: Chemolithotrophs are a subset of autotrophs that use inorganic compounds for energy and utilize CO2 as their primary carbon source.

Question 3

3. Which element is a major component of proteins and nucleic acids?
   A) Carbon
   B) Oxygen
   C) Nitrogen
   D) Phosphorus

Answer 3

C) Nitrogen
Rationale: Nitrogen is an essential component of amino acids (building blocks of proteins) and nucleic acids (DNA and RNA).

Question 4

4. What is the end product of all pathways for nitrogen that most organisms can use?
   A) N2
   B) NO3
   C) NH4
   D) NH3

Answer 4

D) NH3
Rationale: Most organisms can utilize ammonia (NH3) as their nitrogen source.

Question 5

5. What form of nitrogen is most abundant in the Earth’s atmosphere?
   A) N2
   B) NO3
   C) NH4
   D) NH3

Answer 5

A) N2
Rationale: N2, or molecular nitrogen, makes up about 78% of the Earth’s atmosphere.

Question 6

6. Sulfur is an essential component of which molecules?
   A) Carbohydrates
   B) Amino acids
   C) Fatty acids
   D) Monosaccharides

Answer 6

B) Amino acids
Rationale: Sulfur is vital for the functioning of proteins and is an essential component of certain amino acids.

Question 7

7. Which molecule is crucial for storing and transferring energy within cells?
   A) DNA
   B) Glucose
   C) ATP
   D) RNA

Answer 7

C) ATP
Rationale: ATP (Adenosine Triphosphate) is essential for storing and transferring energy in cells.

Question 8

8. Phosphorus is a key component of which cellular structure?
   A) Cell wall
   B) Cytoplasm
   C) Nucleus
   D) Cell membrane

Answer 8

D) Cell membrane
Rationale: Phosphorus is a vital component of phospholipids that form cell membranes.

Question 9

9. In which form do organisms primarily uptake phosphorus from their environment?
   A) Phosphoric acid
   B) Phospholipids
   C) Phosphate ions
   D) Phosphorus gas

Answer 9

C) Phosphate ions
Rationale: Organisms uptake phosphorus in the form of phosphate ions (PO4^3-) from their environment.

Question 10

10. Which mineral is essential for enzymes involved in electron transfer?
    A) Calcium
    B) Magnesium
    C) Iron
    D) Potassium

Answer 10

C) Iron
Rationale: Iron is crucial for enzymes involved in electron transfer and oxygen transportation.

Question 11

11. Which organisms rely on organic carbon for their growth?
    A) Autotrophs
    B) Heterotrophs
    C) Chemolithotrophs
    D) Both A and C

Answer 11

B) Heterotrophs
Rationale: Heterotrophs are organisms that rely on organic carbon, taken from other living organisms, for their growth.

Question 12

12. Magnesium is primarily required for the activity of enzymes associated with which molecule?
    A) DNA
    B) Lipids
    C) ATP
    D) Carbohydrates

Answer 12

C) ATP
Rationale: Magnesium is essential for many enzymes, especially those involved in ATP metabolism.

Question 13

13. Which mineral is NOT crucial for enzyme activity?
    A) Zinc
    B) Iron
    C) Magnesium
    D) Helium

Answer 13

D) Helium
Rationale: Helium is a noble gas and is not known to be essential for any biological processes or enzyme activities in organisms.

Question 14

14. Which process involves the conversion of nitrogen into various forms usable by living organisms?
    A) Photosynthesis
    B) Carbon cycle
    C) Nitrogen cycle
    D) Oxygen cycle

Answer 14

C) Nitrogen cycle
Rationale: The nitrogen cycle consists of processes like nitrogen fixation, nitrification, and denitrification that help convert nitrogen into forms usable by living organisms.

Question 15

15. What do organisms that depend on plants primarily rely on for sulfur?
    A) Proteins
    B) Enzymes
    C) Vitamins
    D) All of the above

Answer 15

D) All of the above
Rationale: Sulfur is an essential component of certain amino acids, vitamins, and is vital for the functioning of proteins and enzymes in plants. Animals that depend on plants would consequently rely on these molecules for their sulfur.

Question 16

1. Which pH range is optimal for most organisms called Neutralophiles?
   A) 3.0
   B) 6.0 - 8.0
   C) 10.5
   D) 2-10

Answer 16

B) 6.0 - 8.0
Rationale: Neutralophiles primarily thrive in a pH range that is near neutral, which is 6.0 to 8.0.

Question 17

2. Acidophiles thrive in environments with a pH of?
   A) 10.5
   B) 5.0
   C) 3.0
   D) 6.5

Answer 17

C) 3.0
Rationale: Acidophiles prefer acidic environments, and they can thrive in conditions as low as pH 3.0.

Question 18

3. Which temperature range is suitable for Psychrophilic organisms?
   A) 20 - 30° C
   B) -5 - 15° C
   C) 30° C
   D) 37° C

Answer 18

B) -5 - 15° C
Rationale: Psychrophilic organisms prefer cold temperatures, and their range is -5 to 15° C.

Question 19

4. Mesophilic organisms have an optimal temperature of?
   A) 30° C
   B) -5° C
   C) 20° C
   D) 15° C

Answer 19

A) 30° C
Rationale: Mesophilic organisms have an optimal temperature around 30° C, which is suitable for many free-living forms.

Question 20

5. Which organisms require oxygen as a hydrogen acceptor?
   A) Facultative Anaerobes
   B) Obligate Aerobes
   C) Obligate Anaerobes
   D) Microaerophiles

Answer 20

B) Obligate Aerobes
Rationale: Obligate aerobes are organisms that strictly require oxygen as their hydrogen acceptor for energy production.

Question 21

6. Which of the following organisms require high salt concentrations?
   A) Mesophiles
   B) Psychrophiles
   C) Halophilic
   D) Osmophilic

Answer 21

C) Halophilic
Rationale: Halophilic organisms thrive in environments with high salt concentrations.

Question 22

7. Which organisms can live both aerobically and anaerobically?
   A) Microaerophiles
   B) Facultative Anaerobes
   C) Obligate Aerobes
   D) Aerotolerant Anaerobes

Answer 22

B) Facultative Anaerobes
Rationale: Facultative anaerobes have the capability to live and grow in both aerobic and anaerobic conditions.

Question 23

8. At which pH level do Alkaliphiles flourish?
   A) 3.0
   B) 6.5
   C) 8.0
   D) 10.5

Answer 23

D) 10.5
Rationale: Alkaliphiles are adapted to alkaline environments and can thrive at a pH as high as 10.5.

Question 24

9. Which organisms are indifferent to oxygen and do not use it as a hydrogen acceptor?
   A) Microaerophiles
   B) Obligate Aerobes
   C) Aerotolerant Anaerobes
   D) Facultative Anaerobes

Answer 24

C) Aerotolerant Anaerobes
Rationale: Aerotolerant anaerobes can grow in the presence of oxygen but do not use it as a hydrogen acceptor.

Question 25

10. Which bacteria require small amounts of oxygen, specifically between 2-10%? A) Obligate Aerobes B) Facultative Anaerobes C) Aerotolerant Anaerobes D) Microaerophiles

Answer 25

D) Microaerophiles Rationale: Microaerophiles are adapted to environments with low oxygen levels and specifically require small amounts of oxygen between 2-10%.

Question 26

11. Psychrotrophs are known to be a cause of what? A) Nitrogen fixation B) Food spoilage C) Oxygen production D) Salt formation

Answer 26

B) Food spoilage Rationale: Psychrotrophs can grow at low temperatures, making them a significant cause of food spoilage in refrigerated foods.

Question 27

12. Which organisms thrive under high osmotic pressures? A) Halophilic B) Mesophilic C) Psychrophilic D) Osmophilic

Answer 27

D) Osmophilic Rationale: Osmophilic organisms are adapted to environments with high osmotic pressures.

Question 28

13. Which bacteria is NOT an obligate anaerobe? A) Actinomyces sp. B) Bacillus sp. C) Clostridium sp. D) Fusobacterium sp.

Answer 28

B) Bacillus sp. Rationale: Bacillus species are typically obligate aerobes or facultative anaerobes, meaning they require or can utilize oxygen, unlike obligate anaerobes.

Question 29

14. Which bacteria is a known microaerophile? A) Lactobacillus sp. B) Campylobacter sp. C) Pseudomonas aeruginosa D) Eubacterium sp.

Answer 29

B) Campylobacter sp. Rationale: Campylobacter species require small amounts of oxygen to thrive, making them microaerophiles.

Question 30

15. Which bacteria grows well in the presence of oxygen but does not use it as a hydrogen acceptor? A) Mycobacterium sp. B) Nocardia sp. C) Lactobacillus sp. D) Helicobacter sp.

Answer 30

C) Lactobacillus sp. Rationale: Lactobacillus species are aerotolerant anaerobes, meaning they can grow in the presence of oxygen but do not use it as a hydrogen acceptor.

Question 31

16. Which organism's growth is not affected by high salt concentration? A) Halophilic B) Mesophilic C) Psychrophilic D) Osmophilic

Answer 31

B) Mesophilic Rationale: Mesophilic organisms primarily focus on moderate temperature conditions and are not specifically adapted to high salt concentrations like Halophilic organisms.

Question 32

17. Which bacteria is an example of an obligate aerobe? A) Clostridium sp. B) Bacteroides sp. C) Pseudomonas aeruginosa D) Fusobacterium sp.

Answer 32

C) Pseudomonas aeruginosa Rationale: Pseudomonas aeruginosa requires oxygen for its metabolic processes, classifying it as an obligate aerobe.

Question 33

18. At which temperature range can Mesophilic organisms grow well, even if it's not their optimal range? A) 20 - 30° C B) -5 - 15° C C) 40 - 50° C D) 10 - 20° C

Answer 33

A) 20 - 30° C Rationale: While the optimal temperature for Mesophilic organisms is around 30° C, they can still grow well in the 20 - 30° C range.

Question 34

19. Which environment would Acidophiles NOT thrive in? A) pH 2.5 B) pH 3.5 C) pH 9.5 D) pH 5.5

Answer 34

C) pH 9.5 Rationale: Acidophiles prefer acidic environments, and a pH of 9.5 is alkaline, making it unsuitable for them.

Question 35

20. Which bacteria is known to be aerotolerant? A) Mycobacterium sp. B) Corynebacterium sp. C) Propionibacterium sp. D) Bacillus sp.

Answer 35

C) Propionibacterium sp. Rationale: Propionibacterium species are aerotolerant anaerobes, which means they can grow in the presence of oxygen but do not use it as a hydrogen acceptor.

Question 36

2. Which medium contains lysed sheep blood hemoglobin? A) MacConkey Agar B) Chocolate Agar C) Thayer-Martin Agar D) Lowenstein-Jensen Agar

Answer 36

B) Chocolate Agar Rationale: Chocolate Agar is specifically made using lysed sheep blood hemoglobin as one of its primary constituents.

Question 37

3. Which agar is selective for Neisseria gonorrhoeae? A) Lowenstein-Jensen Agar B) MacConkey Agar C) Charcoal Yeast Extract Agar D) Thayer-Martin Agar

Answer 37

D) Thayer-Martin Agar Rationale: Thayer-Martin Agar is designed selectively for Neisseria species, including Neisseria gonorrhoeae.

Question 38

4. Which medium is used primarily for Legionella? A) Blood Agar B) Thayer-Martin Agar C) Charcoal Yeast Extract Agar D) MacConkey Agar

Answer 38

C) Charcoal Yeast Extract Agar Rationale: Charcoal Yeast Extract Agar is the primary medium used for growing Legionella.

Question 39

5. Which component in MacConkey Agar serves as an indicator for lactose fermentation? A) Bile salts B) Crystal violet C) Lysed sheep blood D) Neutral red

Answer 39

D) Neutral red Rationale: Neutral red in MacConkey Agar acts as an indicator for lactose fermentation.

Question 40

6. Which medium is selective and differential for Gram-negative bacteria? A) MacConkey Agar B) Blood Agar C) Charcoal Yeast Extract Agar D) Lowenstein-Jensen Agar

Answer 40

A) MacConkey Agar Rationale: MacConkey Agar is specifically formulated to be selective for Gram-negative bacteria and differential based on lactose fermentation.

Question 41

7. Which medium is enriched with egg to enhance growth? A) Chocolate Agar B) Charcoal Yeast Extract Agar C) Thayer-Martin Agar D) Lowenstein-Jensen Agar

Answer 41

D) Lowenstein-Jensen Agar Rationale: Lowenstein-Jensen Agar contains egg as a crucial ingredient to enhance the growth of Mycobacterium.

Question 42

8. For which bacteria is Chocolate Agar primarily used? A) Haemophilus influenzae B) Enterobacteriaceae C) Legionella D) Mycobacterium

Answer 42

A) Haemophilus influenzae Rationale: Chocolate Agar is specially designed for the growth of Haemophilus influenzae.

Question 43

9. Which medium contains four antibiotics to inhibit contaminants? A) Thayer-Martin Agar B) Chocolate Agar C) MacConkey Agar D) Charcoal Yeast Extract Agar

Answer 43

A) Thayer-Martin Agar Rationale: Thayer-Martin Agar is formulated with four antibiotics specifically to inhibit contaminants.

Question 44

10. Which component inhibits contaminants in Lowenstein-Jensen Agar? A) Neutral red B) Malachite green C) Charcoal D) Bile salts

Answer 44

B) Malachite green Rationale: Malachite green in Lowenstein-Jensen Agar serves to inhibit contaminants while promoting the growth of Mycobacterium.

Question 45

11. Which medium is enriched and designed specifically for Mycobacterium? A) Blood Agar B) Lowenstein-Jensen Agar C) MacConkey Agar D) Chocolate Agar

Answer 45

B) Lowenstein-Jensen Agar Rationale: Lowenstein-Jensen Agar is an enriched selective medium used primarily for the growth of Mycobacterium.

Question 46

12. Which component in MacConkey Agar inhibits Gram-positive bacteria? A) Bile salts B) Neutral red C) Lysed sheep blood D) Crystal violet

Answer 46

D) Crystal violet Rationale: In MacConkey Agar, crystal violet is used to inhibit the growth of Gram-positive bacteria.

Question 47

13. Which medium has a primary constituent of nutrient agar combined with sheep's blood? A) Chocolate Agar B) Blood Agar C) Thayer-Martin Agar D) MacConkey Agar

Answer 47

B) Blood Agar Rationale: Blood Agar is a combination of nutrient agar and 5-10% sheep's blood.

Question 48

14. Neisseria meningitidis primarily grows on which medium? A) Charcoal Yeast Extract Agar B) Thayer-Martin Agar C) Lowenstein-Jensen Agar D) Blood Agar

Answer 48

B) Thayer-Martin Agar Rationale: Thayer-Martin Agar is selectively designed for the growth of Neisseria species, including Neisseria meningitidis.

Question 49

15. Which medium contains three antibiotics to inhibit contaminants? A) Thayer-Martin Agar B) Charcoal Yeast Extract Agar C) Lowenstein-Jensen Agar D) Blood Agar

Answer 49

B) Charcoal Yeast Extract Agar Rationale: Charcoal Yeast Extract Agar contains three antibiotics to prevent contamination and promote the growth of Legionella.

Question 50

1. Which phase of the bacterial growth curve represents a period of adaptation? A) LOG Phase B) Stationary Phase C) Lag Phase D) Logarithmic Decline Phase

Answer 50

C) Lag Phase Rationale: During the Lag Phase, cells adjust and adapt to their new environment, having been previously in unfavorable conditions.

Question 51

2. In which phase is the growth rate constant? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 51

B) LOG Phase Rationale: During the LOG (Exponential Growth) Phase, new cell material is synthesized at a constant rate.

Question 52

3. What event causes the transition from the LOG Phase to the Stationary Phase? A) Cells acclimatize to their environment B) Constant synthesis of new cell material C) Depletion of nutrients or accumulation of toxic products D) Increase in death rate

Answer 52

C) Depletion of nutrients or accumulation of toxic products Rationale: The LOG Phase continues until either nutrients are exhausted or toxic metabolic products build up, leading to the Stationary Phase.

Question 53

4. Which phase has a growth rate of zero but doesn’t involve adaptation? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 53

C) Stationary Phase Rationale: The Stationary Phase has a growth rate of zero, due to the exhaustion of nutrients or accumulation of toxic products, and is distinct from the adaptation process seen in the Lag Phase.

Question 54

5. In which phase does the death rate increase steadily? A) LOG Phase B) Stationary Phase C) Lag Phase D) Logarithmic Decline Phase

Answer 54

D) Logarithmic Decline Phase Rationale: The Logarithmic Decline Phase is characterized by an intensified rate of cell death.

Question 55

6. Which phase is characterized by cells being in a balanced state? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 55

B) LOG Phase Rationale: During the LOG Phase, cells are in a steady state, with new cell material being synthesized continuously.

Question 56

7. Which phase immediately follows the adaptation period? A) LOG Phase B) Stationary Phase C) Lag Phase D) Logarithmic Decline Phase

Answer 56

A) LOG Phase Rationale: After cells adapt in the Lag Phase, they enter the LOG Phase, where growth occurs at a constant rate.

Question 57

8. Which phase indicates a negative growth rate? A) LOG Phase B) Stationary Phase C) Lag Phase D) Logarithmic Decline Phase

Answer 57

D) Logarithmic Decline Phase Rationale: The Logarithmic Decline Phase is characterized by a negative growth rate, indicating a net death of cells.

Question 58

9. During which phase is there a balance between cell growth and cell death? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 58

C) Stationary Phase Rationale: In the Stationary Phase, the formation of new cells is offset by cell death, leading to a balanced or zero net growth.

Question 59

10. Which phase can be prolonged by a nutrient-rich environment? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 59

B) LOG Phase Rationale: The LOG Phase, where cells grow at a constant rate, can be extended if the environment remains rich in nutrients.

Question 60

11. In which phase are cells adjusting to previous unfavorable conditions? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 60

A) Lag Phase Rationale: The Lag Phase is when cells, previously in suboptimal conditions, adjust and adapt to their new environment.

Question 61

12. Which phase is primarily driven by the accumulation of toxic by-products? A) LOG Phase B) Stationary Phase C) Lag Phase D) Logarithmic Decline Phase

Answer 61

B) Stationary Phase Rationale: The Stationary Phase can be initiated either by nutrient exhaustion or the buildup of toxic metabolic by-products.

Question 62

13. During which phase do cells not grow due to environmental constraints? A) Lag Phase B) LOG Phase C) Stationary Phase D) Logarithmic Decline Phase

Answer 62

C) Stationary Phase Rationale: The Stationary Phase represents a time when cell growth halts due to factors like nutrient depletion or the presence of toxic substances.

Question 63

14. Which phase is directly after cells have been in a balanced growth state? A) Lag Phase B) Stationary Phase C) Logarithmic Decline Phase D) LOG Phase

Answer 63

B) Stationary Phase Rationale: After the LOG Phase, where cells are in a steady state, they enter the Stationary Phase due to environmental constraints.

Question 64

15. When does the bacterial growth curve represent collective cell population events? A) Only in the Lag Phase B) Only in the LOG Phase C) Throughout all phases D) Only in the Stationary Phase

Answer 64

C) Throughout all phases Rationale: The phases of the bacterial growth curve symbolize collective cell population events, not those of individual cells, across all phases.

Question 65

1. Which bacterial shape is described as spherical or nearly spherical? A) Bacilli B) Vibrio C) Coccus D) Spirochete

Answer 65

C) Coccus Rationale: The coccus shape is described as spherical or nearly spherical, differentiating it from the other shapes mentioned.

Question 66

2. Which bacteria might be found in clusters? A) Corynebacterium B) Streptococcus C) Staphylococcus D) Vibrio cholerae

Answer 66

C) Staphylococcus Rationale: Staphylococci are described as cocci that may occur in clusters.

Question 67

4. Which bacterial form is straight, rod-shaped, and can have tapered ends? A) Spirochetes B) Bacilli C) Vibrio D) Coccus

Answer 67

B) Bacilli Rationale: Bacilli are described as relatively straight, rod-shaped cells that can sometimes have tapered ends.

Question 68

5. Which of the following is NOT a type of Bacilli? A) Clostridium B) Pseudomonas C) Vibrio cholerae D) Bacillus

Answer 68

C) Vibrio cholerae Rationale: Vibrio cholerae is described under the Vibrio category and is not classified as Bacilli.

Question 69

6. Which bacteria are described as having a spiral form? A) Vibrio B) Coccus C) Spirochete D) Bacillus

Answer 69

C) Spirochete Rationale: Spirochetes are described as bacteria that have a spiral form.

Question 70

7. Which bacterial shape is intermediate between spiral and bacilli and often classified as bacilli? A) Coccus B) Vibrio C) Spirochete D) Bacilli

Answer 70

B) Vibrio Rationale: The Vibrio shape is described as being intermediate between spiral and bacilli and often classified as bacilli.

Question 71

8. All helical bacteria are termed as which of the following? A) Bacilli B) Coccus C) Bacillus D) None of the above

Answer 71

D) None of the above Rationale: Not all helical bacteria are termed as spirochetes, so none of the options provided are correct.

Question 72

9. Which bacteria can be described as rod-shaped but with very short lengths sometimes resembling cocci? A) Coccobacilli B) Spirochete C) Vibrio D) Coccus

Answer 72

A) Coccobacilli Rationale: Coccobacilli are described as very short, rod-shaped cells that can sometimes resemble cocci in appearance.

Question 73

10. Which of the following bacteria is associated with the Vibrio shape? A) Bacillus B) Treponema C) Vibrio parahaemolyticus D) Staphylococcus

Answer 73

C) Vibrio parahaemolyticus Rationale: Vibrio parahaemolyticus is directly mentioned as an example of bacteria with a Vibrio shape.

Question 74

11. Neisseria is an example of bacteria with which shape? A) Bacillus B) Coccus C) Spirochete D) Vibrio

Answer 74

B) Coccus Rationale: Neisseria is listed as an example of coccus-shaped bacteria.

Question 75

12. Which shape describes bacteria that are straight, rod-shaped with potential pointed ends termed as fusiform? A) Spirochete B) Bacilli C) Coccus D) Vibrio

Answer 75

B) Bacilli Rationale: Bacilli are described as straight, rod-shaped cells with the potential for pointed ends termed as fusiform.

Question 76

13. What shape is associated with bacteria like Treponema and Borrelia? A) Bacillus B) Coccus C) Spirochete D) Bacilli

Answer 76

C) Spirochete Rationale: Both Treponema and Borrelia are examples of spirochete-shaped bacteria.

Question 77

14. Bacteria that are intermediate in shape between cocci and bacilli but are still often considered cocci are termed as? A) Coccobacilli B) Vibrio C) Spirochete D) Bacillus

Answer 77

A) Coccobacilli Rationale: Coccobacilli are intermediate in shape between cocci and bacilli but are often still considered cocci.

Question 78

15. Which bacterial shape is associated with Haemophilus and Bordetella? A) Coccus B) Bacillus C) Spirochete D) Bacilli

Answer 78

B) Bacillus Rationale: Both Haemophilus and Bordetella are listed as examples of bacteria with a Bacillus shape.

Question 79

1. Which of the following bacterial groups contains members known to produce endospores? A) G(-) B) G(+) C) Both G(-) and G(+) D) None of the above

Answer 79

B) G(+) ONLY: Bacillus, Clostridium, Coxiella

Question 80

What is the primary mechanism by which heat sterilizes materials? a) Oxidation b) Cell dehydration c) Denaturation of cellular proteins and nucleic acids d) Cell respiration inhibition

Answer 80

c) Denaturation of cellular proteins and nucleic acids Rationale: Heat works primarily by denaturing the proteins and nucleic acids within cells, leading to their death. While other mechanisms can also contribute, denaturation is the primary and most effective means by which heat achieves sterilization.

Question 81

Which temperature and duration are commonly used to kill bacterial spores during sterilization? a) 80° C for 30 minutes b) 100° C for 2-3 minutes c) 110° C for 10 minutes d) 121° C for 15 minutes

Answer 81

d) 121° C for 15 minutes Rationale: 121° C for 15 minutes is the recommended setting for autoclaving in order to ensure that bacterial spores, which are more resistant than vegetative cells, are completely killed.

Question 82

Why is steam generally preferred over dry heat for sterilization? a) It's less energy-consuming. b) Bacteria are killed more quickly when moist. c) Steam prevents oxidation of materials. d) It's more cost-effective.

Answer 82

b) Bacteria are killed more quickly when moist. Rationale: Moist heat (steam) penetrates materials more effectively and kills bacteria faster compared to dry heat.

Question 83

Which type of radiation is used for sterilization purposes? a) Visible light b) Infrared radiation c) UV light d) Microwaves

Answer 83

c) UV light Rationale: UV light has germicidal properties and is used in various applications for sterilization. It can damage the DNA of bacteria, preventing them from replicating or functioning.

Question 84

For sterilizing materials that must remain dry, which of the following is typically used? a) Steam autoclave b) Circulating hot air electric ovens c) UV light chambers d) Gamma radiation

Answer 84

b) Circulating hot air electric ovens Rationale: Circulating hot air electric ovens are utilized to sterilize materials that need to stay dry. They provide a controlled environment where heat can be applied consistently for effective sterilization.

Question 85

Which bacterial genus is known to produce spores that can survive extreme heat? a) Escherichia b) Pseudomonas c) Staphylococcus d) Bacillus

Answer 85

d) Bacillus Rationale: The Bacillus genus is known for its ability to produce heat-resistant spores that can survive even in extreme conditions, making it particularly challenging to eradicate using standard heat-based sterilization methods.

Question 86

In the context of sterilization, what advantage does steam have over dry heat? a) It's faster. b) It's safer. c) It's more sustainable. d) It has a lower boiling point.

Answer 86

a) It's faster. Rationale: Steam or moist heat penetrates and kills bacteria more rapidly than dry heat, making it a preferred method for sterilization in many settings.

Question 87

Which of the following is NOT a known mechanism for sterilization by radiation? a) Cell dehydration b) DNA damage c) Oxidative damage d) Protein damage

Answer 87

a) Cell dehydration Rationale: Radiation, especially UV and ionizing radiation, can cause DNA, protein, and oxidative damage, which can lead to cell death. However, dehydration is not a direct mechanism of radiation-induced sterilization.

Question 88

Which component provides resistance to antibacterial chemical agents in endospores? a) Lipid membrane b) Keratin coat c) Calcium dipicolinate d) Peptidoglycan layer

Answer 88

b) Keratin coat Rationale: The keratin coat of an endospore confers impermeability, giving it resistance to antibacterial chemical agents.

Question 89

Which chemical component in endospores provides them with heat resistance? a) Lipopolysaccharide b) Peptidoglycan c) Keratin d) Calcium dipicolinate

Answer 89

d) Calcium dipicolinate Rationale: Calcium dipicolinate, present in endospores, is responsible for providing them with resistance to heat, making them challenging to kill even at elevated temperatures.