Question 1

Which of the following statements best describes the function of peptidoglycan in bacterial cell envelopes?

Accepted Answer

It confers structural strength and helps maintain cell shape.

Question 2

Which scientist is credited with developing the enrichment culture technique and describing the first virus?

Accepted Answer

Martinus Beijerinck

Question 3

A Gram-negative bacterium is characterized by which of the following cell envelope features?

Accepted Answer

A thin peptidoglycan layer and an outer membrane containing lipopolysaccharide (LPS)

Question 4

Which of the following is a physiological process unique to plants and algae among the groups listed?

Accepted Answer

Photosynthesis: $CO_2 + 	ext{Light} \rightarrow O_2 + (CH_2O)_n$

Question 5

Which of the following is NOT a cornerstone of modern microbiology?

Accepted Answer

Photosynthesis

Question 6

What is the main function of the cytoplasmic membrane in bacteria?

Accepted Answer

It acts as a permeability barrier and is involved in energy conservation.

Question 7

Which of the following best explains why oil immersion is used in light microscopy?

Accepted Answer

It reduces light refraction, allowing more light to enter the objective lens and improving resolution.

Question 8

Which of the following is a correct description of the Gram-positive cell envelope?

Accepted Answer

It has a thick peptidoglycan layer and teichoic acids.

Question 9

Which of the following chemical forms is unique to archaeal membrane lipids?

Accepted Answer

Ether-linked phospholipids

Question 10

Which of the following is a direct effect of beta-lactam antibiotics on bacterial cells?

Accepted Answer

Disruption of peptide cross-linking in peptidoglycan, leading to cell lysis

Question 11

Which of the following scientists contributed to the discovery of the structure of DNA?

Accepted Answer

Watson, Crick, and Franklin

Question 12

A student observes two distinct colony types on a streak plate. What is the best next step to obtain pure cultures?

Accepted Answer

Select a single colony from each type and streak onto separate plates.

Question 13

Which of the following is a function of teichoic acids in Gram-positive bacteria?

Accepted Answer

They help anchor the peptidoglycan layer to the cytoplasmic membrane.

Question 14

Which of the following best describes the difference between magnification and resolution in microscopy?

Accepted Answer

Magnification increases image size, while resolution is the smallest distance at which two objects can be distinguished.

Question 15

Which of the following is a plausible consequence of a mutation that prevents cross-linking of peptidoglycan in a bacterium?

Accepted Answer

The bacterium will lose structural integrity and may burst due to osmotic pressure.

Question 16

Which of the following is a correct application of the enrichment culture technique developed by Beijerinck?

Accepted Answer

Isolating microbes capable of nitrogen fixation from soil by providing only $N_2$ as a nitrogen source.

Question 17

Which of the following is a unique feature of the outer membrane in Gram-negative bacteria?

Accepted Answer

It contains lipopolysaccharide (LPS), which can act as an endotoxin.

Question 18

Which of the following best describes the role of the nucleoid in prokaryotic cells?

Accepted Answer

It is the region of the cell where the chromosome is found, not enclosed by a membrane.

Question 19

Which of the following is a correct example of physiological diversity among microbes?

Accepted Answer

Some microbes can use $Fe^{2+}$, $NO_3^-$, or $SO_4^{2-}$ as electron donors or acceptors.

Question 20

Which of the following best explains the importance of the fluid mosaic model in understanding membrane structure?

Accepted Answer

It explains how membrane proteins and lipids can move laterally, allowing dynamic functions.

Microbial Diversity, Cell Envelope Structure, and Cornerstones of Modern Microbiology

Study Guide - Practice Questions