Q: A student is asked to calculate the size difference between a typical virus (20 nm) and a typical bacterium (2 µm). What is the ratio of their sizes?

$$ \frac{2 \times 10$$^{-6}$$ \text{m}}{20 \times 10$$^{-9}$$ \text{m}} = 100 $$

Question 1

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

Accepted Answer

Gram-negative bacteria possess an outer membrane containing lipopolysaccharides that acts as a barrier to many antibiotics.

Question 2

A microbiologist observes spherical bacteria arranged in clusters under the microscope. Which term best describes this morphology?

Accepted Answer

Staphylococci

Question 3

Which component is found in the cell walls of bacteria but NOT in archaea or eukaryotes?

Accepted Answer

Peptidoglycan

Question 4

A student is asked to calculate the size difference between a typical virus (20 nm) and a typical bacterium (2 µm). What is the ratio of their sizes?

Accepted Answer

$$ \frac{2 	imes 10$$^{-6}$$ 	ext{m}}{20 	imes 10$$^{-9}$$ 	ext{m}} = 100 $$

Question 5

Which of the following is a unique feature of archaea that distinguishes them from bacteria?

Accepted Answer

Branched hydrocarbon chains in membrane lipids

Question 6

During Gram staining, what is the primary reason Gram-positive bacteria retain the crystal violet stain?

Accepted Answer

Their thick peptidoglycan layer retains the crystal violet-iodine complex.

Question 7

Which of the following best describes the evolutionary timeline of prokaryotes?

Accepted Answer

Prokaryotes appeared before eukaryotes, around 3.5 billion years ago.

Question 8

Which of the following is NOT a function of the bacterial cell wall?

Accepted Answer

Facilitating active transport of nutrients

Question 9

A scientist is studying a microbe that thrives in extremely salty environments and lacks peptidoglycan in its cell wall. To which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 10

Which of the following statements about the three-domain system is correct?

Accepted Answer

Archaea are more closely related to eukaryotes than to bacteria based on rRNA phylogeny.

Question 11

Which of the following is a real-world application of genetically modified bacteria?

Accepted Answer

Protecting crops from pests and freezing

Question 12

Which of the following is a correct match between cell morphology and arrangement?

Accepted Answer

Cocci arranged in chains are called streptococci.

Question 13

Which of the following is NOT a characteristic of prokaryotic cells?

Accepted Answer

Presence of a distinct nucleus with a membrane

Question 14

Which of the following statements about endospores is correct?

Accepted Answer

Endospores are resistant structures formed by some bacteria to survive harsh conditions.

Question 15

Which of the following is a major difference between eukaryotic and prokaryotic cells?

Accepted Answer

Eukaryotic cells have membrane-enclosed organelles, while prokaryotic cells do not.

Question 16

Which of the following is a correct statement about the size of microbes?

Accepted Answer

Bacteria are generally larger than viruses but smaller than helminths.

Question 17

Which of the following is a plausible reason why the average human contains more bacterial DNA than human DNA?

Accepted Answer

Bacteria outnumber human cells in the body.

Question 18

Which of the following is NOT included in the scope of microbiology?

Accepted Answer

Mammals

Question 19

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

Accepted Answer

Gram-negative bacteria stain red because their thin peptidoglycan layer allows the safranin dye to be visible.

Question 20

Which of the following is a modern use of microbes in biotechnology?

Accepted Answer

Using microbes to produce food and chemicals as miniature biochemical factories

Introduction to Microbiology: Prokaryotes, Cell Structure, and Taxonomy

Study Guide - Practice Questions

Study Guide - Flashcards