+/- Germ Flashcards
What is peptidoglycan?
A: A macromolecular network in the bacterial cell wall made of repeating disaccharides connected by polypeptides.
What are the two monosaccharides in peptidoglycan’s disaccharide structure?
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
How are rows of NAG and NAM linked in peptidoglycan?
A: By polypeptides, forming a carbohydrate “backbone” with peptide cross-bridges.
How does penicillin affect peptidoglycan?
interferes with peptide cross-bridge formation, weakening the cell wall and causing cell lysis.
What is a defining feature of gram-positive cell walls?
A: They have thick layers of peptidoglycan and contain teichoic acids.
Q: What are teichoic acids, and where are they found?
A: Molecules in gram-positive cell walls that regulate cation movement and provide antigenic specificity.
Q: What makes gram-negative cell walls different from gram-positive cell walls?
A: Gram-negative cell walls have a thin peptidoglycan layer and an outer membrane with lipopolysaccharides.
What is the function of the outer membrane in gram-negative bacteria?
It provides protection from phagocytosis, detergents, antibiotics, and more, due to its negative charge and selective permeability
What are porins in gram-negative bacteria?
A: Proteins in the outer membrane that form channels for the passage of molecules like nutrients.
What is the lipopolysaccharide (LPS) in gram-negative bacteria, and what are its components?
A: A molecule in the outer membrane consisting of lipid A, a core polysaccharide, and an O polysaccharide.
Q: What is lipid A and its significance?
A: Lipid A is the lipid part of LPS that is toxic and released when gram-negative bacteria die.
What component functions as an endotoxin in Gram-negative bacteria?
A: Lipid A.
What symptoms are associated with Lipid A in Gram-negative bacterial infections?
Fever, dilation of blood vessels, shock, and blood clotting.
What is the role of the core polysaccharide in Gram-negative bacteria?
A: It provides structural stability.
What makes up the O polysaccharide in Gram-negative bacteria, and what is its function?
The O polysaccharide is composed of sugar molecules and functions as an antigen.
How is E. coli O157:H7 distinguished from other serovars?
A: By specific laboratory tests that detect antigens on the O polysaccharide.
What is the role of the O polysaccharide in distinguishing serovars of Gram-negative bacteria?
A: It serves as an antigen, allowing for differentiation between strains.
The O polysaccharide in Gram-negative bacteria is similar in function to what component in Gram-positive bacteria?
A: Teichoic acids
