Quiz 5 Review Flashcards
What does a positive catalase test indicate?
A) The bacteria can ferment lactose
B) The bacteria can reduce sulfur
C) The bacteria produce the enzyme catalase
D) The bacteria are Gram-positive
C) The bacteria produce the enzyme catalase
Explanation: A positive catalase test indicates that the bacteria produce catalase, an enzyme that breaks down hydrogen peroxide into water and oxygen. This is characteristic of many bacteria, including Staphylococcus species.
True or False: The oxidase test is used to identify bacteria that can perform anaerobic respiration.
A) True
B) False
B) False
Explanation: The oxidase test is used to identify bacteria that have certain cytochrome c oxidases, which are involved in aerobic respiration, not anaerobic.
Fill in the Blank: MacConkey agar is selective and differential media used to isolate ______ bacteria and differentiate them based on ______ fermentation.
Gram-negative; lactose
Explanation: MacConkey agar is designed to isolate Gram-negative enteric bacteria and differentiate between them based on their ability to ferment lactose.
What does the MR test in the MR-VP series stand for and what does it detect?
A) Methyl Red; lactose fermentation
B) Methyl Red; mixed acid fermentation
C) MacConkey Red; sulfur reduction
D) Methane Reductase; methane production
B) Methyl Red; mixed acid fermentation
Explanation: The MR test stands for Methyl Red and is used to detect mixed acid fermentation, which lowers the pH of the medium, turning the methyl red indicator red.
True or False: Sucrose fermentation is typically assessed using TSI slant media.
A) True
B) False
A) True
Explanation: TSI slant media is designed to differentiate enteric bacteria based on their ability to ferment glucose, lactose, and sucrose, as well as their ability to reduce sulfur.
When handling cultures, it is important to gently _______ them without disturbing the setup to prevent false results.
mix
Explanation: Cultures should be gently mixed to ensure even distribution of bacteria and proper testing without causing disturbances that could lead to false results, such as gas production in the Durham tubes.
Which enzyme’s presence is assessed by the oxidase test?
A) Catalase
B) Lactase
C) Oxidase
D) Sucrase
C) Oxidase
Explanation: The oxidase test is used to detect the presence of cytochrome c oxidases in bacteria, which are involved in the electron transport chain of aerobic respiration.
True or False: All bacteria that test positive for the catalase test are also positive on the oxidase test.
A) True
B) False
B) False
Explanation: While both tests involve oxygen, they test for different enzymes. Some bacteria may produce catalase but not cytochrome c oxidases, and vice versa.
What is the role of the cytochrome oxidase complex in the electron transport chain?
A) It directly converts ADP to ATP.
B) It oxidizes NADH to NAD+.
C) It transfers electrons to oxygen, forming water.
D) It pumps protons into the cytoplasm of the bacterial cell.
C) It transfers electrons to oxygen, forming water.
Explanation: The cytochrome oxidase complex, specifically cytochrome a3, transfers electrons to molecular oxygen, reducing it to water. This process is essential for the final step of the electron transport chain in aerobic respiration.
True or False: The presence of NADH dehydrogenase in the electron transport chain means the oxidase test will be positive.
A) True
B) False
B) False
Explanation: NADH dehydrogenase is another component of the electron transport chain but is not related to the cytochrome oxidase complex tested by the oxidase test. The oxidase test specifically checks for the presence of cytochrome c oxidase.
When the oxidase test is positive, ________ oxidase is present.
indophenol
Explanation: The oxidase test indicates the presence of indophenol oxidase, which is part of the cytochrome oxidase complex that catalyzes the transfer of electrons to oxygen, completing the electron transport chain.
Which of the following is not a direct function of the cytochrome oxidase complex?
A) Electron transfer to oxygen
B) Proton pumping
C) ATP synthesis
D) Water formation
C) ATP synthesis
Explanation: The cytochrome oxidase complex is responsible for electron transfer to oxygen and pumping protons across the membrane, contributing to the proton motive force used by ATP synthase to synthesize ATP. It does not directly synthesize ATP itself.
True or False: The oxidase test detects the presence of ATP synthase in the bacterial cell.
A) True
B) False
B) False
Explanation: The oxidase test is designed to detect the presence of the cytochrome c oxidase, specifically the indophenol oxidase, not ATP synthase. ATP synthase is involved in the synthesis of ATP from ADP and Pi, utilizing the proton motive force generated by the electron transport chain.
In the electron transport chain, the final electron acceptor is ________.
oxygen (O₂)
Explanation: In aerobic respiration, the final electron acceptor in the electron transport chain is molecular oxygen (O₂). It is reduced to water (H₂O) by the electrons transferred through the chain.
Which component of the electron transport chain is highlighted by the oxidase test?
A) Cytochrome b-c complex
B) Cytochrome c
C) Cytochrome oxidase complex
D) NADH dehydrogenase complex
C) Cytochrome oxidase complex
Explanation: The oxidase test specifically highlights the presence of the cytochrome oxidase complex, which is the part of the electron transport chain that catalyzes the reduction of oxygen to water.
