Question 1

Which of the following statements best explains why Mycoplasma pneumoniae cannot be identified using a Gram stain?

Accepted Answer

It lacks a cell wall, so the Gram stain has no target to bind.

Question 2

A patient presents with symptoms of gas gangrene after a traumatic injury. Which of the following bacteria is most likely responsible, and what unique feature aids its survival in harsh conditions?

Accepted Answer

Clostridium perfringens; ability to form endospores

Question 3

Which of the following best describes the difference between a provirus and a prophage?

Accepted Answer

A provirus is viral DNA integrated into a eukaryotic host genome, while a prophage is viral DNA integrated into a bacterial genome.

Question 4

Which of the following is a key structural difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have teichoic acids embedded in a thick peptidoglycan layer.

Question 5

A hospital-acquired infection is traced to a bacterium that is catalase-positive, coagulase-positive, and forms golden-yellow colonies. Which organism is most likely responsible?

Accepted Answer

Staphylococcus aureus

Question 6

Which of the following best explains why antibiotics targeting peptidoglycan synthesis are selectively toxic to bacteria but not to human cells?

Accepted Answer

Bacterial cell walls contain peptidoglycan, which is absent in human cells.

Question 7

Which of the following scenarios best illustrates horizontal gene transfer in bacteria?

Accepted Answer

A bacterium acquires a plasmid carrying antibiotic resistance from another bacterium via conjugation.

Question 8

Which of the following best describes the function of the contractile vacuole in protozoa such as Paramecium?

Accepted Answer

It expels excess water to maintain osmotic balance.

Question 9

A patient is diagnosed with malaria. Which organism is responsible, and what is a key diagnostic feature of this parasite?

Accepted Answer

Plasmodium falciparum; ring-shaped trophozoites in red blood cells

Question 10

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause transmissible spongiform encephalopathies.

Question 11

Which of the following best explains why enveloped viruses are generally more sensitive to disinfectants than non-enveloped viruses?

Accepted Answer

Their phospholipid envelope is easily disrupted by detergents and solvents.

Question 12

Which of the following is a distinguishing feature of fungal cell membranes that is targeted by many antifungal medications?

Accepted Answer

Presence of ergosterol

Question 13

A laboratory is using MacConkey agar to differentiate between coliform and non-coliform bacteria. Which result would indicate the presence of a coliform?

Accepted Answer

Growth with pink/red colonies, indicating lactose fermentation

Question 14

Which of the following best describes the process of generalized transduction in bacteriophages?

Accepted Answer

A phage accidentally packages random fragments of host DNA and transfers them to another bacterium.

Question 15

Which of the following equations correctly represents the calculation for the total magnification of a specimen viewed under a compound light microscope?

Accepted Answer

$$	ext{Total Magnification} = 	ext{Objective Lens Magnification} 	imes 	ext{Ocular Lens Magnification}$$

Question 16

A patient is infected with a -ssRNA virus. Which of the following statements about its replication is correct?

Accepted Answer

The virus must carry its own RNA-dependent RNA polymerase to synthesize +ssRNA.

Question 17

Which of the following best describes the difference between mutualism and commensalism in microbial relationships?

Accepted Answer

In mutualism, both organisms benefit; in commensalism, one benefits and the other is unaffected.

Question 18

Which of the following is a correct statement about the ribosomes found in eukaryotic cells?

Accepted Answer

Cytoplasmic ribosomes are 80S, while mitochondrial and chloroplast ribosomes are 70S.

Question 19

A patient is diagnosed with a tapeworm infection after eating undercooked pork. Which group of helminths does this organism belong to, and what is a key morphological feature?

Accepted Answer

Platyhelminthes (Cestodes); segmented, ribbon-like body

Question 20

Which of the following best explains why the use of broad-spectrum antibiotics can lead to opportunistic infections such as those caused by Candida albicans?

Accepted Answer

Broad-spectrum antibiotics disrupt the normal microbiota, reducing competition and allowing opportunistic pathogens to proliferate.

Microbiology Unit 1 Study Guide: Microbial Diversity, Cell Structure, and Acellular Pathogens

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