Question 1

Which scientist is credited with disproving the theory of spontaneous generation using swan-necked flasks and also developed the process of attenuation?

Accepted Answer

Louis Pasteur

Question 2

A patient is diagnosed with tuberculosis, a disease caused by Mycobacterium. Which staining technique would be most appropriate to visualize this bacterium, and why?

Accepted Answer

Acid-fast stain, because Mycobacterium has a waxy cell wall rich in mycolic acid.

Question 3

Which of the following best describes the function of bacterial endospores?

Accepted Answer

They allow bacteria to survive harsh environmental conditions by entering a dormant state.

Question 4

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome, and why?

Accepted Answer

The cell will lose water and undergo plasmolysis (shriveling).

Question 5

Which of the following statements about Gram-negative bacteria is TRUE?

Accepted Answer

They possess an outer membrane containing lipopolysaccharide (LPS), which can act as a toxin.

Question 6

During glycolysis, which of the following is produced per molecule of glucose?

Accepted Answer

$$2$$ molecules of pyruvate, $$2$$ molecules of ATP (net), and $$2$$ molecules of NADH$

Question 7

Which of the following best explains why immersion oil increases the resolution of a light microscope?

Accepted Answer

It decreases light refraction by matching the refractive index of glass, allowing more light to enter the objective lens.

Question 8

A microbiologist is using MacConkey agar to isolate bacteria from a stool sample. What is the primary function of this medium?

Accepted Answer

It is a selective medium that inhibits Gram-positive bacteria, allowing Gram-negative bacteria to grow.

Question 9

Which of the following best describes the difference between catabolism and anabolism?

Accepted Answer

Catabolism breaks down complex molecules to release energy; anabolism synthesizes complex molecules and requires energy.

Question 10

A bacterial culture is maintained in a chemostat. Which phase of the growth curve is this culture kept in, and why?

Accepted Answer

Log (exponential) phase, because fresh nutrients are continuously supplied and waste is removed.

Question 11

Which of the following is a correct example of binomial nomenclature for a bacterium?

Accepted Answer

E. coli

Question 12

A bacterial cell lacking a cell wall is placed in distilled water (a hypotonic solution). What is the most likely outcome?

Accepted Answer

The cell will swell and may burst due to water influx.

Question 13

Which of the following best describes the role of the enzyme's active site in a metabolic reaction?

Accepted Answer

It provides a specific location for substrate binding and catalysis, lowering the activation energy.

Question 14

Which of the following is NOT a function of the bacterial glycocalyx?

Accepted Answer

Energy production via ATP synthesis

Question 15

A microbiologist observes a bacterium with a thick peptidoglycan layer and teichoic acids in its cell wall. After Gram staining, what color will the bacterium appear and why?

Accepted Answer

Purple, because the thick peptidoglycan layer retains the crystal violet-iodine complex.

Question 16

Which of the following best explains why antibiotics that target bacterial ribosomes do not harm human cells?

Accepted Answer

Bacterial ribosomes are 70S, while human (eukaryotic) ribosomes are 80S, allowing selective targeting.

Question 17

Which of the following best describes the difference between aerobic respiration and fermentation in bacteria?

Accepted Answer

Aerobic respiration uses oxygen as the final electron acceptor, while fermentation uses an organic molecule from within the cell.

Question 18

A bacterial population doubles every 30 minutes. If you start with $$100$$ cells, how many cells will there be after $$3$$ hours, assuming unlimited resources?

Accepted Answer

$$6,400$$

Question 19

Which of the following best describes the function of hemolysins when bacteria are grown on blood agar?

Accepted Answer

They lyse red blood cells, creating clear zones around colonies.

Question 20

Which of the following statements about phase-contrast microscopy is TRUE?

Accepted Answer

It is ideal for observing living, unstained cells and their internal structures.

Microbiology Study Guide: Foundations, Cell Structure, Microscopy, Metabolism, and Growth

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