Ch 4 – Microbiology Test Questions – Flashcards

55 test answers

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characteristics of prokaryotes
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-DNA not enclosed in a membrane
-DNA not associated with histones
-no membrane bound organelles
-cell wall of peptidoglycan
-divide by binary fission
-bacteria and archea
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3 basic shapes
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cocci (spheres), bacilli (rods), spiral
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arrangements of cocci
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-diplococci
-streptococci
-tetrad
-sarcinae
-staphylococci
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streptococci
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chains
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tetrad
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group of 4 cocci
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sarcinae
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group of 8 cocci
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staphylococci
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grapelike
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types of bacilli
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-diplobacilli
-streptobacilli
-coccobacilli
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types of spiral
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-vibrio
-spirillum
-spirochete
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vibrio
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curved rods
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spirillum
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helical shape (use flagella)
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spirochete
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helical and flexible (axial filaments)
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3 other shapes
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-star
-rectangle
-triangle
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star
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stella
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rectangular
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haloarcula
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triangular
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angulomicrobium
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external structures to the cell wall
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-glycocalyx
-flagella
-pili/fimbriae
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glycocalyx
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-general term to describe substances that surround the cell
-viscous, sticky, gelatinous polymer of polysaccharides/polypeptides or both
-capsule (organized tight)
-slime layer(loose)
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functions of glycocalyx
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-act as a barrier to toxic hydrophobic molecules (detergents)
-can enable adherence to other bacteria or host tissue (biofilms)
-major virulence factor due to its weak antigenic and antiphagocytic properties
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flagella and types
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-composed of helically coiled proteins (flagellin)
-peritrichous
-monotrichous and polar
-lophotrichous and polar
-amphitrichous
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peritrichous
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distributed over entire cell
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monotrichous and polar
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single flagellum at one pole
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lophotrichous and polar
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many flagella at one pole
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amphitrichous
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flagella at both poles
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flagella movement
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-driven by rotary engine composed of proteins located at flagellum's anchor point on the inner cell membrane (basal body)
-powered by proton motive force
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pili/fimbriae
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-thin protein tubes originating from plasma membrane
-found in all gram negative bacteria
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pili
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-shaft composed of pilin
-involved in motility
-bring bacteria together and allow transfer of DNA (conjugation)
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fimbriae
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-can occur at poles or over entire surface
-promote attachment to other bacteria and host
-virulence factor
-ex. E. coli colonization
-N. gonorihoeae urinary infection
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the cell wall and functions
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-contains semi rigid, tight knit, molecular complex of peptidoglycan(NAG,NAM,peptides)
-protects inside of cell from detrimental changes in the outside environment
-prevents cell from rupturing in hypotonic conditions
-maintains shape
-provides ligands(binds to receptors) for adherence
-essential structure for cell viability
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NAM and NAM
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-linked in rows of 10-65 sugars
-attached to peptide chain of 4 amino acids (direct and cross linked)
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The gram stain
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-named after Hans Christian Gram (1884)
-one of the most important techniques in microbio
-based on ability of bacteria cell wall to retain primary crystal violet dy during solvent treatment
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Gram stain steps
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-apply crystal violet
-apply iodine (mordant)
-decolorize with alcohol
-apply safranin (counterstain)
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Gram + stain mechanism
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-high peptidoglycan
-low lipid
-pores shrink from alcohol
-CVI complex retained
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Gram - stain mechanism
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-low peptidoglycan
-high lipid
-dissolution of lipid membrane from alcohol
-CVI complex washes out
-cell takes up counterstain
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Gram + cell wall characteristics
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-thick peptidoglycan (20-80nm)
-contains teichoic acids (wall and lipo)
-contains alcohol group (glycerol,ribitol) and phosphate group
-may be involved in regulating flow of cations
-important surface antigens involved in adherence
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Gram - cell wall characteristics
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-thin peptidoglycan (7-8nm)
-no teichoic acids
-possesses outer membrane
-lipoprotein bind peptidoglycan to outer membrane
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outer membrane
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-LPS
-lipoproteins
-phospholipids
-porins
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LPS
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-lipid A
-core polysaccharide
-O antigen
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lipid A
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-basic component
-endotoxin activity
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core polysaccharide
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-branched 9-12 sugars
-structural
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O antigen
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-50-100 repeating saccharide units
-allows serotype distinction
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mycoplasma
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-have no cell wall
-plasma membrane contains sterols
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Archea
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-may lack cell wall or are composed of polysaccharides and proteins
-pseudomurein instead of peptidoglycan
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plasma membrane
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-thin semi permeable membrane composed of phospholipid bilayer
-polar ends form innermost and outermost
-peripheral proteins found at innner or outer surface
-integral proteins span membrane or are channels with a pore (transmembrane proteins)
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functions of plasma membrane
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-selective semi permeable membrane that determines what goes on in and out of organism
-breakdown of nutrients
-production of energy (ATP)
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cytoplasm
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-gel like substance
-80% water
-contains proteins, carbs, lipids, inorganic ions. low MW compounds
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major structures of cytoplasm
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-nucleoid
-plasmids
-ribosomes
-inclusions
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nucleoid
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-long single molecule of double stranded helical supercoiled DNA
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plasmids
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-small molecules of double stranded helical non chromosomal DNA
-code for proteins not coded by nucleoid (antibiotic resistance, exotoxins)
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ribosomes
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-composed of rRNA and protein
-composed of two subunits with densities of 30S and 50S
-two subunits combine during protein synthesis to make 70S
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inclusions
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-reserve deposits
-may be starch glycogen, lipids, sulfur, phosphate
-bacteria live in competitive environment where nutrients are in short supply so they store up whenever possible
-gas vacuoles are hollow cylinders that maintain buoyancy
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endospores
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-resistant structures formed by Gram + bacteria under adverse conditions
-most resistant life from known
-able to survive 100 degrees C for long periods
-reisistant to UV light, drying up, and harmful chemicals
-some disease organisms like anthrax and botulism form spores that reside in soil
-size shape and location are genetic characteristics
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formation of endospores
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-spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm
-Plasma membrane starts to surround DNA, cytoplasm, and membrane isolated in step 1
-spore septum surrounds isolated portion forming an forespore
-peptidoglycan layer forms between membranes
-spore coat forms
-endospore is freed from cell
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NAG
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N-acetylglucosamine
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NAM
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N-acetylmuramic acid
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