Microbiology, 3rd Edition (Wessner) - 2025/2026 Study Guide
Chapter 1: The Microbial World
1. What are the three domains of life as defined by Carl Woese?
ANSWER ✓ The three domains are Bacteria, Archaea, and Eukarya.
2. How did the work of Robert Hooke and Antoni van Leeuwenhoek contribute to
the field of microbiology?
ANSWER ✓ Robert Hooke used early microscopes to describe cellular structures,
coining the term "cell." Antoni van Leeuwenhoek was the first to observe and accurately
describe live microorganisms, which he called "animalcules."
3. What is the primary difference between prokaryotic and eukaryotic cells?
ANSWER ✓ Prokaryotic cells (Bacteria and Archaea) lack a membrane-bound nucleus
and other membrane-bound organelles, while eukaryotic cells (Eukarya) possess a
nucleus and various organelles.
4. Why are viruses not considered part of the three-domain system?
ANSWER ✓ Viruses are not considered living organisms by most definitions because
they lack cellular structure, cannot carry out metabolic processes on their own, and are
obligate intracellular parasites that require a host cell to replicate.
5. What is the significance of the endosymbiotic theory?
ANSWER ✓ The endosymbiotic theory explains the origin of certain eukaryotic
organelles. It proposes that mitochondria and chloroplasts evolved from free-living
prokaryotic cells that were engulfed by a larger host cell, leading to a mutually beneficial
symbiotic relationship.
Chapter 2: Microbial Cell Structure and Function
6. What is the primary function of the bacterial cell wall?
ANSWER ✓ The bacterial cell wall provides structural strength, maintains cell shape, and
prevents the cell from osmotic lysis.
7. Differentiate between the structure of Gram-positive and Gram-negative cell
walls.
ANSWER ✓ Gram-positive bacteria have a thick layer of peptidoglycan with teichoic
acids embedded in it. Gram-negative bacteria have a thin layer of peptidoglycan and an
outer membrane containing lipopolysaccharides (LPS).
, 8. What is the medical significance of Lipopolysaccharide (LPS)?
ANSWER ✓ LPS, also known as endotoxin, is a potent stimulator of the immune system.
Its release from Gram-negative bacteria can trigger fever, shock, and other severe
inflammatory responses in the host.
9. What is the function of bacterial flagella?
ANSWER ✓ Flagella are long, whip-like appendages that provide motility, allowing
bacteria to move towards favorable environments (e.g., nutrients) or away from harmful
ones (e.g., toxins).
10. What are pili and what is their role in bacterial conjugation?
ANSWER ✓ Pili (or fimbriae) are hair-like structures on the surface of bacteria. A specific
type, the sex pilus, is used in conjugation to form a bridge between two bacterial cells
for the transfer of genetic material, such as plasmids.
11. Describe the structure and function of the bacterial cytoplasmic membrane.
ANSWER ✓ It is a phospholipid bilayer containing proteins. It acts as a selectively
permeable barrier, facilitates transport, is the site of energy generation (in prokaryotes),
and plays a role in cell division.
12. What are endospores and which genera of bacteria are known to produce
them?
ANSWER ✓ Endospores are highly durable, dormant structures formed by some
bacteria to survive extreme environmental conditions. Key genera
include Bacillus and Clostridium.
13. What is the function of the capsule or slime layer in many bacteria?
ANSWER ✓ The capsule or slime layer (a glycocalyx) aids in attachment to surfaces,
protects against phagocytosis by immune cells, and helps prevent desiccation.
Chapter 3: Microbial Metabolism
14. What is the primary role of enzymes in metabolic reactions?
ANSWER ✓ Enzymes are biological catalysts that speed up the rate of chemical
reactions by lowering the activation energy, without being consumed in the process.
15. Differentiate between catabolism and anabolism.
ANSWER ✓ Catabolism is the process of breaking down molecules to release energy.
Anabolism is the process of using energy to build complex molecules from simpler ones.
Chapter 1: The Microbial World
1. What are the three domains of life as defined by Carl Woese?
ANSWER ✓ The three domains are Bacteria, Archaea, and Eukarya.
2. How did the work of Robert Hooke and Antoni van Leeuwenhoek contribute to
the field of microbiology?
ANSWER ✓ Robert Hooke used early microscopes to describe cellular structures,
coining the term "cell." Antoni van Leeuwenhoek was the first to observe and accurately
describe live microorganisms, which he called "animalcules."
3. What is the primary difference between prokaryotic and eukaryotic cells?
ANSWER ✓ Prokaryotic cells (Bacteria and Archaea) lack a membrane-bound nucleus
and other membrane-bound organelles, while eukaryotic cells (Eukarya) possess a
nucleus and various organelles.
4. Why are viruses not considered part of the three-domain system?
ANSWER ✓ Viruses are not considered living organisms by most definitions because
they lack cellular structure, cannot carry out metabolic processes on their own, and are
obligate intracellular parasites that require a host cell to replicate.
5. What is the significance of the endosymbiotic theory?
ANSWER ✓ The endosymbiotic theory explains the origin of certain eukaryotic
organelles. It proposes that mitochondria and chloroplasts evolved from free-living
prokaryotic cells that were engulfed by a larger host cell, leading to a mutually beneficial
symbiotic relationship.
Chapter 2: Microbial Cell Structure and Function
6. What is the primary function of the bacterial cell wall?
ANSWER ✓ The bacterial cell wall provides structural strength, maintains cell shape, and
prevents the cell from osmotic lysis.
7. Differentiate between the structure of Gram-positive and Gram-negative cell
walls.
ANSWER ✓ Gram-positive bacteria have a thick layer of peptidoglycan with teichoic
acids embedded in it. Gram-negative bacteria have a thin layer of peptidoglycan and an
outer membrane containing lipopolysaccharides (LPS).
, 8. What is the medical significance of Lipopolysaccharide (LPS)?
ANSWER ✓ LPS, also known as endotoxin, is a potent stimulator of the immune system.
Its release from Gram-negative bacteria can trigger fever, shock, and other severe
inflammatory responses in the host.
9. What is the function of bacterial flagella?
ANSWER ✓ Flagella are long, whip-like appendages that provide motility, allowing
bacteria to move towards favorable environments (e.g., nutrients) or away from harmful
ones (e.g., toxins).
10. What are pili and what is their role in bacterial conjugation?
ANSWER ✓ Pili (or fimbriae) are hair-like structures on the surface of bacteria. A specific
type, the sex pilus, is used in conjugation to form a bridge between two bacterial cells
for the transfer of genetic material, such as plasmids.
11. Describe the structure and function of the bacterial cytoplasmic membrane.
ANSWER ✓ It is a phospholipid bilayer containing proteins. It acts as a selectively
permeable barrier, facilitates transport, is the site of energy generation (in prokaryotes),
and plays a role in cell division.
12. What are endospores and which genera of bacteria are known to produce
them?
ANSWER ✓ Endospores are highly durable, dormant structures formed by some
bacteria to survive extreme environmental conditions. Key genera
include Bacillus and Clostridium.
13. What is the function of the capsule or slime layer in many bacteria?
ANSWER ✓ The capsule or slime layer (a glycocalyx) aids in attachment to surfaces,
protects against phagocytosis by immune cells, and helps prevent desiccation.
Chapter 3: Microbial Metabolism
14. What is the primary role of enzymes in metabolic reactions?
ANSWER ✓ Enzymes are biological catalysts that speed up the rate of chemical
reactions by lowering the activation energy, without being consumed in the process.
15. Differentiate between catabolism and anabolism.
ANSWER ✓ Catabolism is the process of breaking down molecules to release energy.
Anabolism is the process of using energy to build complex molecules from simpler ones.
