FIRST AID FOR THE USMLE EXAM REVIEW
SOLVED QUESTIONS WITH VERIFIED
ANSWERS SHEET
●● *Flagellum* on bacteria is composed of what? What is the function?
Answer: Composition: Proteins
Function: motility
●● *Pilus/Fimbria* on bacteria is composed of what? What is the
function?
Answer: Composition: Glycoprotein
Function: Mediate adherence of bacteria to cell surface, sex plus during
conjugation.
●● *Spore* formation is ONLY possible is what type of bacteria? Why
is the formation of spores important/beneficial?
What is the composition of a spore?
Answer: Gram Positive Only
Function: Resistant to dehydration, heat, and chemicals.
Composition: Keratin-like coat; dipicolinic acid; peptidoglycan.
,●● *Capsule* will be composed of what on bacteria? What is the benefit
of a capsule?
Answer: Function: Protects against phagocytosis
Composition: Organized, discrete polysaccharide layer (except Bacillus
anthracis, which contains d-glutamate)
●● Glycocalyx
Answer: Function: Mediates adherance to surfaces, especially foreign
surfaces (e.g., indwelling catheters)
Composition:Loose network of polysaccharides
●● Periplasm
Answer: Space between the cytoplasmic membrane and outer membrane
in gram-negative bacteria
(peptidoglycan in the middle)
Gram Neg only
Accumulates components exiting gram neg cells, including hydrolytic
enzymes (β-lactamases)
●● Outer membrane (gram negatives)
,Answer: Gram Neg Only
Function:
1. Endotoxin: Lipid A induces TNF and IL-1; O polysaccharide is
antigenic
2. Most OMPs are antigenic
Porins: transport across outer membrane
Composition:
1. Outer Leaflet: endotoxin lipopolysaccharide [LPS/LOS]
2. Embedded proteins: porins and other outer membrane proteins
(OMPs)
3. Inner Leaflet: phospholipids
●● Cell wall and Gram Stain
Answer: Composition: Peptidoglycan is a sugar backbone with peptide
chains cross-linked by transpeptidase
Function: Net-like structure give rigid support, protects against osmotic
pressure damage.
Gram Stain:
Thick peptidoglycan layer retains crystal violet = gram +
, Thin peptidoglycan layer turns red or pink with counterstain = gram -
●● Cytoplasmic Membrane
Answer: Composition: Phospholipid bilayer sac with embedded proteins
(PBP's) and other enzymes.
Lipoteichoic acids (gram Pos+ only) extend from membrane exterior.
Function: Site of oxidative and transport enzymes
PBPs involved in cell wall synthesis
Lipoteichoic acids induce TNF and IL-1
●● Plasmid
Answer: -Contains a variety of genes for antibiotic resistance, enzymes,
and toxins
-Composed of DNA
●● Gram-positive spherical (coccus) bacteria
Answer: -Staphylococcus (clusters)
-Streptococcus (chains, pairs)
●● Gram-positive rod (bacillus) bacteria
Answer: -Bacillus
-Clostridium
SOLVED QUESTIONS WITH VERIFIED
ANSWERS SHEET
●● *Flagellum* on bacteria is composed of what? What is the function?
Answer: Composition: Proteins
Function: motility
●● *Pilus/Fimbria* on bacteria is composed of what? What is the
function?
Answer: Composition: Glycoprotein
Function: Mediate adherence of bacteria to cell surface, sex plus during
conjugation.
●● *Spore* formation is ONLY possible is what type of bacteria? Why
is the formation of spores important/beneficial?
What is the composition of a spore?
Answer: Gram Positive Only
Function: Resistant to dehydration, heat, and chemicals.
Composition: Keratin-like coat; dipicolinic acid; peptidoglycan.
,●● *Capsule* will be composed of what on bacteria? What is the benefit
of a capsule?
Answer: Function: Protects against phagocytosis
Composition: Organized, discrete polysaccharide layer (except Bacillus
anthracis, which contains d-glutamate)
●● Glycocalyx
Answer: Function: Mediates adherance to surfaces, especially foreign
surfaces (e.g., indwelling catheters)
Composition:Loose network of polysaccharides
●● Periplasm
Answer: Space between the cytoplasmic membrane and outer membrane
in gram-negative bacteria
(peptidoglycan in the middle)
Gram Neg only
Accumulates components exiting gram neg cells, including hydrolytic
enzymes (β-lactamases)
●● Outer membrane (gram negatives)
,Answer: Gram Neg Only
Function:
1. Endotoxin: Lipid A induces TNF and IL-1; O polysaccharide is
antigenic
2. Most OMPs are antigenic
Porins: transport across outer membrane
Composition:
1. Outer Leaflet: endotoxin lipopolysaccharide [LPS/LOS]
2. Embedded proteins: porins and other outer membrane proteins
(OMPs)
3. Inner Leaflet: phospholipids
●● Cell wall and Gram Stain
Answer: Composition: Peptidoglycan is a sugar backbone with peptide
chains cross-linked by transpeptidase
Function: Net-like structure give rigid support, protects against osmotic
pressure damage.
Gram Stain:
Thick peptidoglycan layer retains crystal violet = gram +
, Thin peptidoglycan layer turns red or pink with counterstain = gram -
●● Cytoplasmic Membrane
Answer: Composition: Phospholipid bilayer sac with embedded proteins
(PBP's) and other enzymes.
Lipoteichoic acids (gram Pos+ only) extend from membrane exterior.
Function: Site of oxidative and transport enzymes
PBPs involved in cell wall synthesis
Lipoteichoic acids induce TNF and IL-1
●● Plasmid
Answer: -Contains a variety of genes for antibiotic resistance, enzymes,
and toxins
-Composed of DNA
●● Gram-positive spherical (coccus) bacteria
Answer: -Staphylococcus (clusters)
-Streptococcus (chains, pairs)
●● Gram-positive rod (bacillus) bacteria
Answer: -Bacillus
-Clostridium
