Question 1

Which of the following best explains why bacteria were present in the final step of Pasteur's swan-neck flask experiment but not in the first step?

Accepted Answer

The flask was tilted, allowing trapped microbes from the neck to reach the sterile broth.

Question 2

According to Koch's postulates, which step is necessary to confirm that a specific microbe causes a disease?

Accepted Answer

The suspected agent must be found in every case of the disease and absent from healthy hosts.

Question 3

A microbiologist observes a cell under a bright field microscope after Gram staining. The cell appears pink. What does this indicate about the cell wall structure?

Accepted Answer

The cell is Gram-negative with a thin peptidoglycan layer.

Question 4

Which of the following microscopes would be best for observing the 3D surface structure of a virus interacting with a host cell?

Accepted Answer

Scanning electron microscope (SEM)

Question 5

Which bacterial structure is primarily responsible for motility by rotating like a propeller?

Accepted Answer

Flagellum

Question 6

A researcher observes that sodium ions ($$\mathrm{Na^+}) $$move into a cell despite a higher concentration inside than outside, and this process requires ATP. What type of transport is this?

Accepted Answer

Active transport

Question 7

Which of the following is NOT a variable that can affect bacterial growth in a laboratory setting?

Accepted Answer

Type of microscope used

Question 8

Which statement best describes the function of the bacterial capsule?

Accepted Answer

It protects the bacterium and helps it attach to surfaces.

Question 9

A medical researcher notes that water moves freely across the cell membrane through special protein channels. What are these channels called?

Accepted Answer

Aquaporins

Question 10

Which of the following best explains why antibiotics are generally more effective against Gram-positive bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan cell wall.

Question 11

Which flagellar arrangement is described as having flagella distributed all over the surface of the bacterial cell?

Accepted Answer

Peritrichous

Question 12

Which statement about biofilms is correct?

Accepted Answer

Biofilms can form on teeth and medical devices, leading to dental plaque and device-related infections.

Question 13

Which of the following is a correct match between organism and its cellular characteristics?

Accepted Answer

Protozoa: Unicellular, eukaryote, contains nucleus

Question 14

Which of the following best describes the function of plasmids in bacteria?

Accepted Answer

They are small circular DNA molecules that can carry antibiotic resistance genes.

Question 15

A Gram stain is performed on a bacterial sample. Which chemical property of the cell wall determines whether the cell stains purple or pink?

Accepted Answer

Thickness of the peptidoglycan layer

Question 16

Which of the following is a correct example of passive transport across a cell membrane?

Accepted Answer

Oxygen passing directly through the phospholipid bilayer without a protein

Question 17

Which bacterial structure is responsible for the synthesis of proteins?

Accepted Answer

Ribosome

Question 18

A scientist wants to observe unstained living bacteria to study their internal structures. Which microscope should they use?

Accepted Answer

Phase contrast microscope

Question 19

Which of the following best describes the relationship between biofilms, teeth, and medical devices?

Accepted Answer

Biofilms can form on both teeth and medical devices, leading to dental plaque and device-related infections.

Question 20

Which of the following correctly matches the bacterial cell structure with its function?

Accepted Answer

Nucleoid: Region containing most of the genetic material (DNA)

Fundamental Concepts in Microbiology: Cell Structure, Growth, and Laboratory Techniques

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