Unit 8 Flashcards
True or False: Organisms that are oxidase positive cannot perform aerobic respiration.
A) True
B) False
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.
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.
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.
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
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.
Organisms that are poisoned by oxygen and do not utilize it at all are known as _______________.
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.
True or False: Facultative anaerobes can only metabolize energy aerobically.
A) True
B) False
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.
Organisms that require low levels of oxygen and may prefer elevated CO2 levels are called __________.
Microaerophiles
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
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.
Which bacterial species is used as a positive control for catalase test?
A) Streptococcus pyogenes
B) Staphylococcus aureus
C) Clostridium difficile
D) Mycobacterium tuberculosis
B) Staphylococcus aureus
Which vial represents obligate anaerobes?
A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5
B) Vial 2
Explanation: Obligate anaerobes are found only at the bottom of the tube, away from oxygen.
Which vial indicates microaerophiles?
A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5
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.
What kind of respiration do obligate anaerobes perform?
A) Aerobic respiration
B) Anaerobic respiration
C) Both A and B
D) Neither A nor B
B) Anaerobic respiration
True or False: The catalase enzyme is used to convert oxygen to hydrogen peroxide.
A) True
B) False
B) False
Explanation: Catalase does the opposite; it breaks down hydrogen peroxide into water and oxygen, helping to protect the cell from oxidative damage.
What is the product of the oxidase reaction: O2 + 4H+ + 4e- → ?
A) H2O2
B) 2 H2O
C) O3
D) CO2
B) 2 H2O
Explanation: The oxidase reaction involves the reduction of molecular oxygen to water in the electron transport chain.
True or False: Obligate aerobes are killed by oxygen.
A) True
B) False
B) False
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
B) Catalase test
Complete the catalase reaction formula:
2 H2O2 → _______ + _______
2H2O + O2
Explanation: The catalase reaction breaks down two molecules of hydrogen peroxide into two molecules of water and one molecule of oxygen gas.
Which vial represents aerotolerant organisms?
A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5
E) Vial 5
Explanation: Aerotolerant organisms show uniform growth throughout the tube, indicating indifference to the presence of oxygen.
_______________ can grow in the presence or absence of oxygen and prefer to use aerobic respiration when oxygen is present.
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.
Which vial represents obligate aerobes?
A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5
A) Vial 1
Explanation: Obligate aerobes grow only at the top of the tube where oxygen is most abundant.
What type of organisms require oxygen to survive?
A) Obligate anaerobes
B) Facultative anaerobes
C) Obligate aerobes
D) Aerotolerant anaerobes
C) Obligate aerobes
In the electron transport chain, cytochrome c oxidase catalyzes the reduction of molecular oxygen to form _________.
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.
True or False: Microaerophiles require the same concentration of oxygen as is present in the atmosphere for growth.
A) True
B) False
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.
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
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.
_________ anaerobes can grow in the presence or absence of oxygen.
Facultative
True or False: The catalase reaction produces hydrogen peroxide as a byproduct.
A) True
B) False
B) False
Explanation: The catalase reaction actually breaks down hydrogen peroxide into water and oxygen, not the other way around.
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
C) Aerotolerant anaerobes
The oxidase test is useful to help distinguish the oxidase positive bacteria Pseudomonas, Neisseria, and _____________ from other Gram-negative bacteria.
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.
_______________ are organisms that require low concentrations of oxygen, higher concentrations are inhibitory to them.
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.
Fill in the Blank: In the presence of the enzyme indophenol oxidase, the reagent in the oxidase test turns ___________.
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.
Fill in the Blank: In the oxidase reaction, oxygen (O2) is reduced by electrons (e−) and protons (H+) to form _______.
Water (H2O)
Explanation: The oxidase reaction is the final step in the electron transport chain where oxygen is reduced to water.
Which type of bacteria are likely to be oxidase positive?
A) Obligate aerobes
B) Obligate anaerobes
C) Facultative anaerobes
D) Both A and C
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.
The _________ test checks for the presence of the enzyme that detoxifies H2O2 by breaking it down into water and oxygen.
Catalase
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
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.
Which vial represents facultative anaerobes ?
A) Vial 1
B) Vial 2
C) Vial 3
D) Vial 4
E) Vial 5
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.
True or False: The indophenol oxidase test can only be used for bacteria that perform anaerobic respiration.
A) True
B) False
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.
The catalase reaction breaks down hydrogen peroxide into water and _________.
Oxygen
Explanation: Catalase is an enzyme that protects the cell by breaking down hydrogen peroxide, which can be harmful, into water and oxygen.
True or False: Obligate anaerobes can survive in the presence of oxygen.
A) True
B) False
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.
