Unit 8

Question 1

True or False: Organisms that are oxidase positive cannot perform aerobic respiration.

A) True
B) False

Answer 1

B) False

Explanation: Oxidase positive organisms have the cytochrome oxidase complex and can perform aerobic respiration. The presence of the enzyme indophenol oxidase, detected by the oxidase test, is a hallmark of organisms capable of using oxygen in the electron transport chain.

Question 2

What is the role of indophenol oxidase in bacteria?

A) It participates in fermentation.
B) It is part of the electron transport chain and works with oxygen.
C) It helps bacteria move.
D) It is used to break down large food particles.

Answer 2

B) It is part of the electron transport chain and works with oxygen.

Explanation: Indophenol oxidase is an enzyme that is involved in the electron transport chain, specifically in the cytochrome oxidase complex, which is the final step in aerobic respiration for bacteria.

Question 3

Which type of organisms requires oxygen for their survival and generates energy only through aerobic respiration?

A) Obligate aerobes
B) Obligate anaerobes
C) Facultative anaerobes
D) Microaerophiles

Answer 3

A) Obligate aerobes

Explanation: Obligate aerobes strictly require oxygen for survival because their energy production is solely reliant on aerobic respiration, a process that uses oxygen to convert glucose into energy, carbon dioxide, and water.

Question 4

Organisms that are poisoned by oxygen and do not utilize it at all are known as _______________.

Answer 4

Obligate anaerobes

Explanation: Obligate anaerobes are unique in their inability to tolerate oxygen, which distinguishes them from other bacteria that can perform anaerobic respiration but can also tolerate or utilize oxygen when it’s available.

Question 5

True or False: Facultative anaerobes can only metabolize energy aerobically.

A) True
B) False

Answer 5

B) False

Explanation: Facultative anaerobes are not restricted to one type of metabolic process. They prefer aerobic respiration due to its efficiency but can survive using anaerobic metabolism when oxygen is not available, giving them a survival advantage in fluctuating environments.

Question 6

Organisms that require low levels of oxygen and may prefer elevated CO2 levels are called __________.

Answer 6

Microaerophiles

Question 7

What is the main function of the oxidase enzyme in the electron transport chain?

A) To produce hydrogen peroxide
B) To break down glucose
C) To transfer electrons to oxygen
D) To synthesize ATP directly

Answer 7

C) To transfer electrons to oxygen

Explanation: The oxidase enzyme, specifically cytochrome c oxidase, transfers electrons to molecular oxygen, reducing it to water at the end of the electron transport chain.

Question 8

Which bacterial species is used as a positive control for catalase test?

A) Streptococcus pyogenes
B) Staphylococcus aureus
C) Clostridium difficile
D) Mycobacterium tuberculosis

Answer 8

B) Staphylococcus aureus

Question 9

Which vial represents obligate anaerobes?

A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5

Answer 9

B) Vial 2

Explanation: Obligate anaerobes are found only at the bottom of the tube, away from oxygen.

Question 10

Which vial indicates microaerophiles?

A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5

Answer 10

D) Vial 4

Explanation: Microaerophiles are concentrated in the upper part of the tube but not at the very top, indicating a preference for lower oxygen concentrations.

Question 11

What kind of respiration do obligate anaerobes perform?

A) Aerobic respiration
B) Anaerobic respiration
C) Both A and B
D) Neither A nor B

Answer 11

B) Anaerobic respiration

Question 12

True or False: The catalase enzyme is used to convert oxygen to hydrogen peroxide.

A) True
B) False

Answer 12

B) False

Explanation: Catalase does the opposite; it breaks down hydrogen peroxide into water and oxygen, helping to protect the cell from oxidative damage.

Question 13

What is the product of the oxidase reaction: O2 + 4H+ + 4e- → ?

A) H2O2
B) 2 H2O
C) O3
D) CO2

Answer 13

B) 2 H2O

Explanation: The oxidase reaction involves the reduction of molecular oxygen to water in the electron transport chain.

Question 14

True or False: Obligate aerobes are killed by oxygen.

A) True
B) False

Answer 14

B) False

Question 15

Which test is used to identify if bacteria can break down hydrogen peroxide?

A) Oxidase test
B) Catalase test
C) Gram stain
D) Coagulase test

Answer 15

B) Catalase test

Question 16

Complete the catalase reaction formula:

2 H2O2 → _______ + _______

Answer 16

2H2O + O2

Explanation: The catalase reaction breaks down two molecules of hydrogen peroxide into two molecules of water and one molecule of oxygen gas.

Question 17

Which vial represents aerotolerant organisms?

A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5

Answer 17

E) Vial 5

Explanation: Aerotolerant organisms show uniform growth throughout the tube, indicating indifference to the presence of oxygen.

Question 18

_______________ can grow in the presence or absence of oxygen and prefer to use aerobic respiration when oxygen is present.

Answer 18

Facultative anaerobes

Explanation: Facultative anaerobes are adaptable organisms that can switch between aerobic respiration when oxygen is present (which is more efficient) and anaerobic processes when it is not. This allows them to thrive in varied environmental conditions.

Question 19

Which vial represents obligate aerobes?

A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5

Answer 19

A) Vial 1

Explanation: Obligate aerobes grow only at the top of the tube where oxygen is most abundant.

Question 20

What type of organisms require oxygen to survive?

A) Obligate anaerobes
B) Facultative anaerobes
C) Obligate aerobes
D) Aerotolerant anaerobes

Answer 20

C) Obligate aerobes

Question 21

In the electron transport chain, cytochrome c oxidase catalyzes the reduction of molecular oxygen to form _________.

Answer 21

Water

Explanation: Cytochrome c oxidase helps to reduce oxygen to water, which is the final step in the electron transport chain, enabling the chain to continue as electrons flow to oxygen.

Question 22

True or False: Microaerophiles require the same concentration of oxygen as is present in the atmosphere for growth.

A) True
B) False

Answer 22

B) False

Explanation: Microaerophiles require oxygen because they use it in aerobic respiration, but they can only tolerate it at much lower concentrations than are found in the atmosphere. High concentrations of oxygen can be damaging to them due to limited detoxifying enzymes.

Question 23

Which organisms are not poisoned by oxygen but do not use it to generate energy?

A) Obligate aerobes
B) Aerotolerant organisms
C) Microaerophiles
D) Facultative anaerobes

Answer 23

B) Aerotolerant organisms

Explanation: Aerotolerant organisms do not use oxygen for growth or energy production, but they are not harmed by its presence. They metabolize energy typically through fermentation, regardless of whether oxygen is available.

Question 24

_________ anaerobes can grow in the presence or absence of oxygen.

Answer 24

Facultative

Question 25

True or False: The catalase reaction produces hydrogen peroxide as a byproduct. A) True B) False

Answer 25

B) False Explanation: The catalase reaction actually breaks down hydrogen peroxide into water and oxygen, not the other way around.

Question 26

What describes bacteria that do not use oxygen but are not harmed by its presence? A) Microaerophiles B) Obligate anaerobes C) Aerotolerant anaerobes D) Facultative anaerobes

Answer 26

C) Aerotolerant anaerobes

Question 27

The oxidase test is useful to help distinguish the oxidase positive bacteria Pseudomonas, Neisseria, and _____________ from other Gram-negative bacteria.

Answer 27

Helicobacter and Campylobacter Explanation: The oxidase test helps distinguish oxidase positive genera like Pseudomonas, Neisseria, Helicobacter, and Campylobacter from other Gram-negative bacteria that are oxidase negative.

Question 28

_______________ are organisms that require low concentrations of oxygen, higher concentrations are inhibitory to them.

Answer 28

Microaerophiles Explanation: Microaerophiles are adapted to environments with lower levels of oxygen than are found in the atmosphere. They often inhabit niches where oxygen is present but at reduced levels, such as in soil or in the human body.

Question 29

Fill in the Blank: In the presence of the enzyme indophenol oxidase, the reagent in the oxidase test turns ___________.

Answer 29

purple Explanation: When the oxidase test is positive, the reagent changes color to purple, indicating that the enzyme indophenol oxidase is present and has oxidized the reagent.

Question 30

Fill in the Blank: In the oxidase reaction, oxygen (O2) is reduced by electrons (e−) and protons (H+) to form _______.

Answer 30

Water (H2O) Explanation: The oxidase reaction is the final step in the electron transport chain where oxygen is reduced to water.

Question 31

Which type of bacteria are likely to be oxidase positive? A) Obligate aerobes B) Obligate anaerobes C) Facultative anaerobes D) Both A and C

Answer 31

D) Both A and C Explanation: Obligate aerobes and facultative anaerobes can both be oxidase positive because they can have the cytochrome oxidase complex that functions in aerobic respiration. Microaerophiles, which are not listed, can also be oxidase positive.

Question 32

The _________ test checks for the presence of the enzyme that detoxifies H2O2 by breaking it down into water and oxygen.

Answer 32

Catalase

Question 33

Which type of bacteria uses anaerobic respiration or fermentation because they are often killed by the presence of oxygen? A) Obligate aerobes B) Obligate anaerobes C) Facultative anaerobes D) Microaerophiles

Answer 33

B) Obligate anaerobes Explanation: Obligate anaerobes are organisms for which even small amounts of oxygen can be lethal. They lack the enzymatic machinery needed to effectively neutralize reactive oxygen species, making environments with normal atmospheric levels of oxygen hazardous for them.

Question 34

Which vial represents facultative anaerobes ? A) Vial 1 B) Vial 2 C) Vial 3 D) Vial 4 E) Vial 5

Answer 34

C) Vial 3 Explanation: Facultative anaerobes grow throughout the medium but are most dense at the top where oxygen is plentiful because they prefer aerobic respiration.

Question 35

True or False: The indophenol oxidase test can only be used for bacteria that perform anaerobic respiration. A) True B) False

Answer 35

B) False Explanation: The indophenol oxidase test is used for bacteria that perform aerobic respiration, as the enzyme indophenol oxidase is part of the cytochrome oxidase complex, which functions only in the presence of oxygen.

Question 36

The catalase reaction breaks down hydrogen peroxide into water and _________.

Answer 36

Oxygen Explanation: Catalase is an enzyme that protects the cell by breaking down hydrogen peroxide, which can be harmful, into water and oxygen.

Question 37

True or False: Obligate anaerobes can survive in the presence of oxygen. A) True B) False

Answer 37

B) False Explanation: Obligate anaerobes are harmed by oxygen due to the absence of the necessary enzymes to detoxify oxygen radicals. They rely on anaerobic processes, such as fermentation, for energy production.