Question 1

Which of the following statements best explains why viruses are considered acellular and nonliving?

Accepted Answer

They cannot carry out metabolism or reproduce independently outside a host cell.

Question 2

A patient is diagnosed with tuberculosis. Which unique feature of the causative agent's cell wall makes it resistant to many disinfectants and difficult to treat?

Accepted Answer

High content of mycolic acid

Question 3

Which of the following best describes the function of the O antigen in the lipopolysaccharide (LPS) of Gram-negative bacteria?

Accepted Answer

It provides antigenic variability, helping bacteria evade the immune system.

Question 4

A scientist isolates a microorganism that is unicellular, lacks a nucleus, and has a cell wall containing peptidoglycan. Which domain does this organism belong to?

Accepted Answer

Bacteria

Question 5

Which of the following is a correct application of Koch’s postulates in establishing a causative relationship between a microbe and a disease?

Accepted Answer

The microbe must be isolated from a diseased host and grown in pure culture.

Question 6

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

Accepted Answer

They possess an outer membrane that acts as a permeability barrier.

Question 7

A hospital patient develops a persistent infection on a catheter. Laboratory analysis reveals a dense community of bacteria embedded in an extracellular matrix. Which process most likely contributed to the increased antibiotic resistance observed in this infection?

Accepted Answer

Biofilm formation and quorum sensing

Question 8

Which of the following is a key difference between the lytic and lysogenic cycles of bacteriophage replication?

Accepted Answer

The lytic cycle leads to rapid production of new viruses and host cell death, while the lysogenic cycle allows the viral genome to persist in the host without immediate lysis.

Question 9

Which of the following best describes the process of group translocation in prokaryotes?

Accepted Answer

An active process where substances are chemically modified as they are transported into the cell.

Question 10

A researcher is studying a microorganism that is multicellular, eukaryotic, and absorbs nutrients from decaying organic matter. Its cell wall is composed of chitin. Which group does this organism most likely belong to?

Accepted Answer

Fungi

Question 11

Which of the following is a distinguishing feature of Mycoplasma species compared to most other bacteria?

Accepted Answer

They lack a cell wall entirely and are naturally resistant to beta-lactam antibiotics.

Question 12

Which of the following best describes the main function of the Golgi apparatus in eukaryotic cells?

Accepted Answer

It modifies, sorts, and packages proteins and lipids for transport.

Question 13

A scientist observes a cell with the following features: linear chromosomes, 80S ribosomes, and membrane-bound organelles. Which equation best represents the number of chromosomes after mitosis if the original cell is diploid with $n$ chromosomes?

Accepted Answer

$n$ in each of two daughter cells, so total $2n$

Question 14

Which of the following scenarios best illustrates receptor-mediated endocytosis?

Accepted Answer

A cell takes in cholesterol by binding LDL particles to specific surface receptors before internalizing them.

Question 15

Which of the following best explains why prions are unique among infectious agents?

Accepted Answer

They are infectious proteins that lack nucleic acids and cause neurodegenerative diseases.

Question 16

A patient presents with a rapidly growing, poorly defined mass that invades surrounding tissues and has spread to distant organs. Which of the following best describes this neoplasm?

Accepted Answer

Malignant neoplasm

Question 17

Which of the following best describes the transition from a proto-oncogene to an oncogene?

Accepted Answer

A proto-oncogene is mutated or overexpressed, leading to uncontrolled cell division.

Question 18

Which of the following is a correct statement about the Gram stain technique?

Accepted Answer

Gram-positive bacteria retain the crystal violet stain due to a thick peptidoglycan layer.

Question 19

Which of the following best explains why endospores are clinically significant in hospital settings?

Accepted Answer

They are dormant structures highly resistant to heat, chemicals, and radiation, making infections difficult to eliminate.

Question 20

A virus is classified as a retrovirus. Which enzyme does it use to replicate its genome, and what is the direction of information flow?

Accepted Answer

Reverse transcriptase; RNA $\rightarrow$ DNA

Comprehensive Study Guide: Microbiology Foundations, Prokaryotic & Eukaryotic Cells, and Viruses

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