MICR 271 EXAM QUESTIONS WITH ALL REVISED ANSWERS
O-Antigen in lipopolysaccharide - Answer-may contain hundreds of repeating units that are species specific
- external to the cell, accessible for interactions with immune cells
Core in lipopolysaccharide - Answer-formed by an array of sugars in...
MICR 271 EXAM QUESTIONS WITH
ALL REVISED ANSWERS
O-Antigen in lipopolysaccharide - Answer-may contain hundreds of repeating units that
are species specific
- external to the cell, accessible for interactions with immune cells
Core in lipopolysaccharide - Answer-formed by an array of sugars including
ketodeoxyoctonate
- inner core is external to the membrane, but close to the surface of the cell
- cross links ionically with other components of the membrane
Lipid A in lipopolysaccharide - Answer-anchors the molecule to the OM
- only component inserted into the OM
Fluid mosaic model - Answer-describes floating proteins within a lipid bilayer
Hopanoids - Answer-Structurally similar to sterols
- help membranes withstand damaging stress conditions
Facilitated diffusion - Answer-molecules move from an area of high concentration to an
area of low concentration via a carrier molecule
- no energy is required
Primary active transport - Answer-molecules are moved from an area of low
concentration to high concentration
- requires ATP
Secondary active transport - Answer-uses the movement of one molecule down its
concentration gradient to facilitate the transport of a second molecule against its
concentration gradient
Group translocation - Answer-an organic molecule is transported across the membrane
into the cell in conjunction with chemical modification
- e.g. glucose being phosphorylated
Iron uptake - Answer-bacterial pathogens require iron and it must be taken up from the
extracellular environment
1. transferrin and iron can cross the outer membrane as a complex, and the iron then
passes through the inner membrane alone - requires ATP
2. some bacteria produce and secrete siderophores, molecules with a high affinity for
iron. once the iron-siderophore complex reaches the cell surface, it binds to a
,siderophore-receptor protein and the whole complex is transported via multiple steps
into the cytoplasm
Endospore - Answer-a resistant asexual spore that develops inside some bacteria cells
to help them survive periods of low nutrient levels and moisture
Endospore formation - Answer-1. vegetative bacterium, a symmetrically dividing cellular
form
2. asymmetric division of the cell results in two compartments. the larger compartment
is the mother cell and the smaller is the forespore
3. peptidoglycan within the septum between the two compartments is degraded and the
forespore is engulfed by the mother cell, forming a cell within a cell
4. the cortex, a thick layer of specialized peptidoglycan is formed
5. coat synthesis begins. the endospore coat is composed of proteins that provide much
of the chemical and enzymatic resistance to degradation
6. coat synthesis is completes, and there is an increase in refractility and heat
resistance
7. lysis of the mother cell liberates the endospore
Capsule - Answer-layer of material attached firmly to an individual bacterium
- offer protection by masking the bacteria from the immune system and antibiotics
during infection, and by helping to prevent desiccation during transmission from host to
host
Slime - Answer-a layer that consists of diffuse, unorganized material that is easily
removed
- offer protection by masking the bacteria from the immune system and antibiotics
during infection, and by helping to prevent desiccation during transmission from host to
host
Biofilm - Answer-consists of polysaccharides surrounding groups of bacteria
- heterogeneous - contain different types of organisms
- important for bacterial colonization of both environmental and host surfaces
S-layer - Answer-a glycoprotein component of the cell envelope
- commonly found in archaea and many types of bacteria
- 2D crystalline arrays that coat the entire cell, consisting of one or more layers of S-
layer proteins
- rarely found with a capsule or slime layer
- provide protection from the immune system and bacteriophage invasion, and increase
structural stability of the cell wall
Flagella - Answer-frequently used for movement in liquid environments
peritrichous flagella - Answer-peritrichous bacteria have flagella surrounding the entire
periphery of the cell
, - present on enterobacteriaceae
Single/polar flagella - Answer-exist of desulfobivrio
Lophotrichous flagella - Answer-tufts of flagella at one end of a bacterium
- present on alcaligenes faecalis
Bipolar flagella - Answer-single flagellum on both ends of the bacterium
- present on helicobacter hepaticus
Flagellar structure - Answer-must be firmly anchored to the cell wall but still be able to
spin very fast
- portion of the flagellum associated with the cell wall is called the basal body
- basal body is anchored in the outer membrane and peptidoglycan via the P- and L-
rings
Pili - Answer-used in a specialized form of motility on solid surfaces called "twitching"
- assembles at the cell surface by the addition of protein subunits at their base
Sex pili - Answer-provide a conduit for the exchange of genetic information via
conjugation
Three domains of life - Answer-Bacteria, Archaea, Eukaryota
If a eukaryote has a membrane-enclosed nucleus, a prokaryote has: - Answer-a
nucleoid, not membrane enclosed
If a eukaryote has lysosomes/peroxisomes, a prokaryote has: - Answer-not present
If a eukaryote has an endoplasmic reticulum/golgi apparatus, a prokaryote has: -
Answer-not present
If a eukaryote has a mitochondria, a prokaryote has: - Answer-not present
Bacteria - Answer-Domain of unicellular prokaryotes that have cell walls containing
peptidoglycan
Archaea - Answer-Domain of unicellular prokaryotes that have cell walls that do not
contain peptidoglycan
Eukaryota - Answer-Domain of organisms that contain a nucleus and other membrane
enclosed organelles
endosymbiont hypothesis - Answer-eukaryotes evolved from prokaryotes, based on the
similarities found between bacteria and mitochondria
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