Question 1

Which of the following best describes the Germ Theory of Disease?

Accepted Answer

Diseases are caused by specific microorganisms that invade the body.

Question 2

Which scientist is credited with providing the first visual evidence of microorganisms using a microscope, leading to the hypothesis that microbes exist?

Accepted Answer

Antonie van Leeuwenhoek

Question 3

A researcher is using a microscope to observe a virus that is approximately 100 nm in diameter. Which type of microscope is most appropriate for this observation?

Accepted Answer

Transmission electron microscope

Question 4

Which of the following statements correctly compares prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have their DNA enclosed in a nucleus, while prokaryotic cells do not.

Question 5

A bacterial culture is growing in a medium and its optical density (OD) is measured over time. The OD increases rapidly, then plateaus. Which phase of growth is represented by the plateau?

Accepted Answer

Stationary phase

Question 6

Which of the following best describes the role of NADH in cellular metabolism?

Accepted Answer

NADH is a carrier of electrons, transferring them to the electron transport chain for ATP production.

Question 7

Which of the following equations correctly represents the Central Dogma of molecular biology?

Accepted Answer

$DNA \rightarrow RNA \rightarrow Protein$

Question 8

A microbiologist is studying a bacterium that can grow in the presence or absence of oxygen. Which term best describes this organism?

Accepted Answer

Facultative anaerobe

Question 9

Which of the following best explains why Gram-negative bacteria are generally more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria have an outer membrane that restricts entry of many antibiotics.

Question 10

Which of the following is an example of mutualism in a microbial ecosystem?

Accepted Answer

Bacteria in the human gut that produce vitamins in exchange for nutrients.

Question 11

A food scientist is designing a method to preserve food by reducing water activity. Which of the following best explains why this method is effective?

Accepted Answer

Lowering water activity inhibits microbial growth by causing cells to lose water via osmosis.

Question 12

Which of the following best describes the process of bioremediation?

Accepted Answer

Using microbes to degrade or detoxify environmental pollutants.

Question 13

A patient is prescribed antibiotics that disrupt the normal gut microbiome. Which of the following is a likely consequence?

Accepted Answer

Increased susceptibility to opportunistic pathogens such as Clostridioides difficile.

Question 14

Which of the following best describes the role of methanogenic archaea in the carbon cycle?

Accepted Answer

They produce methane from carbon dioxide and hydrogen in anaerobic environments.

Question 15

A culture of bacteria is exposed to a hypertonic solution. What is the most likely cellular response?

Accepted Answer

The cell will lose water and shrink due to osmosis.

Question 16

Which of the following best explains why pasteurization is effective in preventing food spoilage?

Accepted Answer

It reduces the number of pathogenic and spoilage microbes by heating food to a specific temperature.

Question 17

Which of the following equations represents the calculation of bacterial population growth during the exponential phase, where $N_0$ is the initial number of cells, $n$ is the number of generations, and $N$ is the final number of cells?

Accepted Answer

$N = N_0 	imes 2^n$

Question 18

Which of the following is a key reason why the use of agar, as introduced by Fanny Hesse, was critical for the development of microbiology?

Accepted Answer

Agar remains solid at incubation temperatures, allowing for the isolation of pure microbial colonies.

Question 19

A wastewater treatment plant uses the measurement of Biochemical Oxygen Demand (BOD) to assess water quality. What does a high BOD indicate?

Accepted Answer

The water contains a high level of organic matter that can be degraded by microbes.

Question 20

Which of the following best describes the process of industrial-scale fermentation in the production of antibiotics?

Accepted Answer

It relies on the metabolic activities of specific microbes to produce antibiotics in large bioreactors.

MCB 100 Exam 1 Study Guide: Foundations and Applications of Microbiology

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