Question 1

Which of the following statements best explains why Archaea are classified separately from Bacteria, despite both being prokaryotic?

Accepted Answer

Archaea possess unique membrane lipids and distinct ribosomal RNA sequences, as shown by Carl Woese's phylogenetic analysis.

Question 2

A patient presents with a persistent lung infection. Laboratory analysis reveals the causative agent is acid-fast. Which cell wall component is most responsible for this staining property?

Accepted Answer

Mycolic acid

Question 3

Which of the following best describes the main difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and teichoic acids, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide.

Question 4

During the Gram-staining procedure, what is the primary reason Gram-negative bacteria appear pink after the final step?

Accepted Answer

The alcohol decolorizer dissolves the outer membrane and allows the safranin counterstain to color the thin peptidoglycan layer.

Question 5

Which of the following is NOT a step in the scientific naming (binomial nomenclature) of microorganisms?

Accepted Answer

The species name is always written before the genus name.

Question 6

A microbiologist is trying to distinguish between two bacterial species using a biochemical test that detects the presence of catalase. Which equation best represents the reaction catalyzed by catalase?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 7

Which of the following best describes the evidence supporting the theory of endosymbiosis for the origin of mitochondria?

Accepted Answer

Mitochondria contain circular DNA and ribosomes similar to those of bacteria.

Question 8

A hospital-acquired infection is traced to a biofilm on a catheter. Which property of biofilms most contributes to their medical significance?

Accepted Answer

Cells in biofilms are more resistant to antibiotics due to the extracellular matrix and altered gene expression.

Question 9

Which of the following statements about viruses is correct?

Accepted Answer

Viruses are obligate intracellular parasites and are classified based on their nucleic acid type and replication strategy.

Question 10

A bacterial culture is incubated at 4°C, 25°C, 37°C, and 60°C. Growth is observed only at 4°C and 10°C. Which term best describes this organism?

Accepted Answer

Psychrophile

Question 11

Which of the following best explains why Mycoplasma species are resistant to antibiotics like penicillin?

Accepted Answer

They lack a cell wall, so antibiotics targeting peptidoglycan synthesis are ineffective.

Question 12

Which of the following is a key difference between light microscopy and transmission electron microscopy (TEM)?

Accepted Answer

TEM provides much higher resolution by using electron beams, allowing visualization of internal cell structures.

Question 13

A Gram-negative bacterium is exposed to lysozyme. What is the most likely outcome, and why?

Accepted Answer

The bacterium is partially protected because the outer membrane limits lysozyme access to the thin peptidoglycan layer.

Question 14

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

Accepted Answer

They allow bacteria to survive extreme environmental conditions such as heat, desiccation, and chemicals.

Question 15

A microbiologist is using a differential medium to distinguish between lactose-fermenting and non-lactose-fermenting bacteria. Which of the following best describes this type of medium?

Accepted Answer

Differential medium

Question 16

Which of the following statements about the nucleoid in prokaryotic cells is correct?

Accepted Answer

It contains a single, circular DNA molecule and is not membrane-bound.

Question 17

Which of the following best explains why motility is advantageous for bacteria in a natural environment?

Accepted Answer

Motility enables bacteria to move toward nutrients and away from harmful substances (chemotaxis), increasing survival.

Question 18

Which of the following best describes the difference between taxonomy and phylogenetics?

Accepted Answer

Taxonomy involves naming and classifying organisms, while phylogenetics focuses on their evolutionary relationships using genetic data.

Question 19

A facultative anaerobe is grown in a test tube of thioglycollate broth. Where would you expect to see the most growth, and why?

Accepted Answer

Throughout the tube, but more at the top where oxygen is present, because it can use both aerobic and anaerobic metabolism.

Question 20

Which of the following best describes the function of eukaryotic ribosomes?

Accepted Answer

They synthesize proteins by translating mRNA.

Biology 152: Microbiology Exam 1 Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards