TeXes Science Practice Test

What type of organism requires oxygen for cellular respiration and cannot grow without it?

1. Obligate aerobes

2. Aerotolerant anaerobes

3. Facultative anaerobes

4. Microaerophiles

The correct answer is: Obligate aerobes

Obligate aerobes are organisms that require oxygen for cellular respiration and cannot survive in environments without it. They rely on aerobic respiration to produce ATP, as oxygen is a crucial electron acceptor in the process. This dependency on oxygen means that obligate aerobes have developed metabolic pathways and cellular machinery that operate efficiently only in the presence of oxygen, making them unable to grow or reproduce in anaerobic conditions. Other types of organisms, such as facultative anaerobes, can grow either in the presence or absence of oxygen, utilizing anaerobic processes when oxygen is not available. Aerotolerant anaerobes can tolerate oxygen but do not use it for growth; they instead rely on fermentation. Microaerophiles require lower levels of oxygen than what is found in the atmosphere but are not strictly dependent on it in the same way as obligate aerobes. Understanding these distinctions is crucial in microbiology and helps in determining the appropriate conditions for cultivating different types of microorganisms.