Question 1

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

Accepted Answer

Their outer membrane acts as a selective barrier, containing porins that exclude many harmful substances.

Question 2

A scientist isolates a unicellular organism from a hot spring. The organism lacks peptidoglycan in its cell wall, has branched membrane lipids, and no known pathogenicity. To which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 3

Which of the following best describes the process of dehydration synthesis in the formation of a disaccharide?

Accepted Answer

A water molecule is removed as two monosaccharides are joined by a glycosidic bond.

Question 4

A patient is diagnosed with tuberculosis. Which staining technique would be most appropriate to identify the causative agent, and what unique cell wall component does this technique detect?

Accepted Answer

Acid-fast stain; detects mycolic acid

Question 5

Which of the following best explains why water is an excellent solvent for most cellular chemistry?

Accepted Answer

Water has polar covalent bonds, allowing it to dissolve other polar and ionic substances.

Question 6

A bacterial cell is placed in a hypotonic solution. What is the most likely outcome if the cell wall is damaged?

Accepted Answer

The cell will take on water and may lyse.

Question 7

Which of the following best describes the function of phospholipids in the plasma membrane?

Accepted Answer

They create a selectively permeable, amphipathic bilayer that allows certain molecules to pass.

Question 8

Which of the following is a limitation of Koch’s postulates when identifying the causative agent of a disease?

Accepted Answer

Some pathogens cannot be cultured outside of a host cell.

Question 9

A virus with a single-stranded RNA genome that is directly translated by host ribosomes is classified as:

Accepted Answer

Single-stranded positive-sense RNA (ssRNA+)

Question 10

Which of the following best explains why RNA viruses mutate more rapidly than DNA viruses?

Accepted Answer

RNA polymerases lack proofreading ability, leading to more errors during replication.

Question 11

Which of the following best describes the process of antigenic shift in influenza viruses?

Accepted Answer

Major genetic reassortment when two different viral strains coinfect a cell, leading to new viral strains.

Question 12

Which of the following is a correct statement about the structure of eukaryotic flagella?

Accepted Answer

They are made of tubulin with a 9+2 arrangement and move in a wavelike motion.

Question 13

A laboratory technician is using a compound light microscope with a 40× objective lens and a 10× ocular lens. What is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 14

Which of the following best describes the role of a mordant in a staining procedure?

Accepted Answer

It interacts with the dye to fix it on the specimen, enhancing contrast.

Question 15

Which of the following is a function of the normal microbiota in humans?

Accepted Answer

They train the immune system and help digest food.

Question 16

Which of the following best explains why phospholipids are suitable for forming plasma membranes, while purely hydrophilic or hydrophobic molecules are not?

Accepted Answer

Phospholipids are amphipathic, allowing them to form a bilayer with hydrophilic heads facing water and hydrophobic tails facing inward.

Question 17

A scientist is studying a microbe that can only be visualized using electron microscopy, contains either DNA or RNA but not both, and requires a host cell for replication. What is the most likely identity of this microbe?

Accepted Answer

Virus

Question 18

Which of the following best describes the function of ribosomes in both prokaryotic and eukaryotic cells?

Accepted Answer

They link amino acids together to form proteins.

Question 19

Which of the following is a correct statement about the difference between simple and differential staining techniques?

Accepted Answer

Differential staining uses multiple dyes to highlight differences between cell types or structures.

Question 20

A patient is infected with a virus that integrates its genome into the host DNA and can remain dormant for years before causing symptoms. Which term best describes this type of infection?

Accepted Answer

Latent infection

Microbiology Foundations: Cells, Biochemistry, and Viruses

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