MCAT Biology : Bacteria and Types of Prokaryotes

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #31 : Bacteria And Types Of Prokaryotes

Which of the following will not survive in the presence of oxygen?

Possible Answers:

Constitutive aerobe

Constitutive anaerobe

Obligate aerobe

Facultative anaerobe

Obligate anaerobe

Correct answer:

Obligate anaerobe

Explanation:

Obligate anaerobes are incapable of producing energy in the presence of oxygen, and can only metabolize compounds via fermentation and anaerobic respiration. Oxygen acts as a toxin to obligate anaerobes.

In contrast, obligate aerobes are only capable of aerobic cellular respiration and cannot survive in the absence of oxygen. Facultative anaerobes are capable of multiple respiration mechanisms and can continue to generate energy in a fluctuating atmosphere, in either the presence or absence of oxygen.

Example Question #71 : Microbiology

Prokaryotes that can utilize oxygen if available, but do not require it, are called __________.

Possible Answers:

constitutive aerobes

constitutive anaerobes

obligate aerobes

obligate anaerobes

facultative anaerobes

Correct answer:

facultative anaerobes

Explanation:

Facultative anaerobes are adaptive prokaryotes that can survive in either aerobic or anaerobic environments. These organisms are capable of both cellular respiration, through use of the electron transport chain along the cell membrane, and fermentation. They will adopt the more efficient process (cellular respiration) when oxygen is present, but can easily switch between one metabolism and the other.

Obligate anaerobes cannot produce energy in the presence of oxygen, and obligate aerobes cannot produce energy in the absence of oxygen.

Example Question #31 : Bacteria And Types Of Prokaryotes

All of the following are true about bacilli bacteria except:

I. All bacilli are rod-shaped

II. All bacilli are gram positive

III. All bacilli are aerobic

Possible Answers:

II only

I and III

III only

II and III

Correct answer:

II and III

Explanation:

Bacilli is a genus of bacteria that are characterized by their rod-shaped cells. Bacilli can be either gram positive, such as Bacillus anthracis, or gram negative, such as Salmonella enterica. Bacilli bacteria can be either aerobic (require oxygen) or facultative anaerobes (can thrive in both oxygen rich and oxygen poor environment). Bacilli are not exclusively aerobic, nor are they exclusively gram positive.

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