BACTERIAL MORPHOLOGY, CELL WALL STRUCTURE, AND
CLASSIFICATION |THE SMART WAY TO PASS | REAL TESTS,
REAL RESULTS!
What is bacterial morphology? Answer: The study of the shape and arrangement of bacteria.
What are the three main shapes of bacteria? Answer: Spherical (coccus), rod-shaped (bacillus),
and curved.
What determines the arrangement of bacterial cells? Answer: The plane of division and how
cells separate.
What happens when bacterial cells separate on a single plane? Answer: They form long chains.
What is the primary component of bacterial cell walls? Answer: Peptidoglycan.
What is the function of the bacterial cell wall? Answer: To protect the plasma membrane and
prevent osmotic lysis.
What is osmotic lysis? Answer: When the internal pressure of a cell exceeds the external
pressure, causing it to burst.
What is peptidoglycan composed of? Answer: A polymer of disaccharides N-acetylglucosamine
(NAG) and N-acetylmuramic acid (NAM).
How does penicillin affect bacterial cells? Answer: It disables the amino acid connections in the
peptidoglycan, causing the cell wall to collapse.
What distinguishes Gram-positive bacteria from Gram-negative bacteria? Answer: Gram-
positive bacteria have thick peptidoglycan layers, while Gram-negative bacteria have thin layers
and an outer membrane.
What are teichoic acids? Answer: Chemicals that anchor the thick peptidoglycan layer to the
plasma membrane in Gram-positive bacteria.
What is the role of lipopolysaccharides (LPS) in Gram-negative bacteria? Answer: They form
an outer membrane that provides protection from antibiotics and phagocytes.
What is an acid-fast stain used for? Answer: To diagnose the presence of mycobacteria, which
have a waxy cell wall.
What is the significance of mycolic acids in acid-fast bacteria? Answer: They make the cells
waxy and difficult to stain, requiring heat to penetrate.
APPHIA – Crafted with Care and Precision for Academic Excellence.
1
, What is the structure of Gram-negative cell walls? Answer: They consist of a thin
peptidoglycan layer surrounded by an outer membrane.
How do Gram-negative bacteria resist lysozymes? Answer: The LPS layer prevents lysozymes
from reaching the peptidoglycan layer.
What is the purpose of the teichoic acids in Gram-positive bacteria? Answer: They may
regulate the movement of cations and provide structural support.
What is the function of the periplasmic space in Gram-negative bacteria? Answer: It contains
enzymes and proteins that aid in nutrient processing and transport.
What is the role of polysaccharides in the cell wall of Gram-positive bacteria? Answer: They
provide antigenic variation and help the immune system recognize different bacterial strains.
What is the difference between wall teichoic acids and lipoteichoic acids? Answer: Wall
teichoic acids link peptidoglycan layers, while lipoteichoic acids anchor the wall to the plasma
membrane.
What is a common example of a pathogenic Gram-negative bacterium? Answer: Escherichia
coli O157:H7, which causes severe food poisoning.
What is the significance of the unique O polysaccharide structure in bacteria? Answer: It helps
the immune system produce specific antibodies against that bacterial strain.
Why are Gram-negative bacteria often more resistant to antibiotics? Answer: Due to their outer
membrane that protects them from antibiotic penetration.
What is the primary function of the plasma membrane in bacterial cells? Answer: To regulate
the movement of substances in and out of the cell.
What is the function of porins in Gram-negative bacteria? Answer: Porins are specific
transporter proteins that selectively move nutrients and vitamins across the outer membrane.
What is the periplasmic space? Answer: The periplasmic space is the area between the two
layers of the cell envelope filled with a gel containing degradative enzymes.
Why do drugs that disrupt the cell wall not work against Gram-negative bacteria? Answer: The
LPS layer prevents drug molecules from entering the periplasmic space, or enzymes in the space
deactivate them.
What is lipid A? Answer: Lipid A is the toxic lipid portion of lipopolysaccharides (LPS) found
in the outer membrane of Gram-negative bacteria.
APPHIA – Crafted with Care and Precision for Academic Excellence.
2
CLASSIFICATION |THE SMART WAY TO PASS | REAL TESTS,
REAL RESULTS!
What is bacterial morphology? Answer: The study of the shape and arrangement of bacteria.
What are the three main shapes of bacteria? Answer: Spherical (coccus), rod-shaped (bacillus),
and curved.
What determines the arrangement of bacterial cells? Answer: The plane of division and how
cells separate.
What happens when bacterial cells separate on a single plane? Answer: They form long chains.
What is the primary component of bacterial cell walls? Answer: Peptidoglycan.
What is the function of the bacterial cell wall? Answer: To protect the plasma membrane and
prevent osmotic lysis.
What is osmotic lysis? Answer: When the internal pressure of a cell exceeds the external
pressure, causing it to burst.
What is peptidoglycan composed of? Answer: A polymer of disaccharides N-acetylglucosamine
(NAG) and N-acetylmuramic acid (NAM).
How does penicillin affect bacterial cells? Answer: It disables the amino acid connections in the
peptidoglycan, causing the cell wall to collapse.
What distinguishes Gram-positive bacteria from Gram-negative bacteria? Answer: Gram-
positive bacteria have thick peptidoglycan layers, while Gram-negative bacteria have thin layers
and an outer membrane.
What are teichoic acids? Answer: Chemicals that anchor the thick peptidoglycan layer to the
plasma membrane in Gram-positive bacteria.
What is the role of lipopolysaccharides (LPS) in Gram-negative bacteria? Answer: They form
an outer membrane that provides protection from antibiotics and phagocytes.
What is an acid-fast stain used for? Answer: To diagnose the presence of mycobacteria, which
have a waxy cell wall.
What is the significance of mycolic acids in acid-fast bacteria? Answer: They make the cells
waxy and difficult to stain, requiring heat to penetrate.
APPHIA – Crafted with Care and Precision for Academic Excellence.
1
, What is the structure of Gram-negative cell walls? Answer: They consist of a thin
peptidoglycan layer surrounded by an outer membrane.
How do Gram-negative bacteria resist lysozymes? Answer: The LPS layer prevents lysozymes
from reaching the peptidoglycan layer.
What is the purpose of the teichoic acids in Gram-positive bacteria? Answer: They may
regulate the movement of cations and provide structural support.
What is the function of the periplasmic space in Gram-negative bacteria? Answer: It contains
enzymes and proteins that aid in nutrient processing and transport.
What is the role of polysaccharides in the cell wall of Gram-positive bacteria? Answer: They
provide antigenic variation and help the immune system recognize different bacterial strains.
What is the difference between wall teichoic acids and lipoteichoic acids? Answer: Wall
teichoic acids link peptidoglycan layers, while lipoteichoic acids anchor the wall to the plasma
membrane.
What is a common example of a pathogenic Gram-negative bacterium? Answer: Escherichia
coli O157:H7, which causes severe food poisoning.
What is the significance of the unique O polysaccharide structure in bacteria? Answer: It helps
the immune system produce specific antibodies against that bacterial strain.
Why are Gram-negative bacteria often more resistant to antibiotics? Answer: Due to their outer
membrane that protects them from antibiotic penetration.
What is the primary function of the plasma membrane in bacterial cells? Answer: To regulate
the movement of substances in and out of the cell.
What is the function of porins in Gram-negative bacteria? Answer: Porins are specific
transporter proteins that selectively move nutrients and vitamins across the outer membrane.
What is the periplasmic space? Answer: The periplasmic space is the area between the two
layers of the cell envelope filled with a gel containing degradative enzymes.
Why do drugs that disrupt the cell wall not work against Gram-negative bacteria? Answer: The
LPS layer prevents drug molecules from entering the periplasmic space, or enzymes in the space
deactivate them.
What is lipid A? Answer: Lipid A is the toxic lipid portion of lipopolysaccharides (LPS) found
in the outer membrane of Gram-negative bacteria.
APPHIA – Crafted with Care and Precision for Academic Excellence.
2
