EXAM 2 P4 Flashcards
cell envelope
refers to everything surrounding the cell, including the membranes, wall, s-layer, capsule
cell wall
refers to the structural element defining the cell shape; the strength element preventing the cell from popping, aka peptidoglycan layer
it is ONE PART of the cell envelope
gram positive cells
has an ester linked cytoplasmic membrane with a thick peptidoglycan cell wall outside. NO OUTER MEMBRANE
gram negative cells
has an ester linked cytoplasmic membrane with a thin peptidoglycan cell wall. has an outer membrane
periplasm
the space between 2 membranes
peptidoglycan wall is within this space
components of the cell wall
also known as murein or peptidoglycan
peptide is attached to sugars. short in length so they are not proteins.
diamino acid has 2 amino groups. the amino groups are needed to make peptide bonds
structure of cell walls
glycan are long strands
peptides on the outside
peptide side chains link glycan strands together to form crosslinks
these are polymerized into one single molecule
transglycosylase
makes the glycan strand by polymerization
transpeptidase
make the peptide strands into crosslinks.
as new units are added, they’re cleaving off a terminal D and using this energy to form more chains
bactoprenol
lipid carrier for precursor transport
autolysins
means self-lysing, causing the cell to burst
cleave peptidoglycan bonds to allow expansion and insertion of new material
PBPs
penicillin binding proteins that catalyze both the glycosyltransferase and transpeptidase activities
degradation of bacterial cell walls
antibiotics, like penicillin, prevent crosslinking and cause the cell to burst
lysozymes cleave glyosidic bonds between NAG and NAM
prokaryotes that can live without cell walls
very few
mycoplasma (bacteria)
thermoplasma (archaea)
only within an isotonic environment
teichoic acid
found in gram positive cell walls
a polymer containing ribitol and sugar with phosphates attached. they are attached to the lipids and peptidoglycan
phosphates provide a negative charge to the cell surface
lipid A
found in gram negative cells
makes up the outer membrane outer leaflet
lipopolysaccharide (LPS)
attached to lipid A
porin proteins
nonselective pores that let a lot of small molecules cross the outer membrane
lipoprotein
attaches the outer membrane to the peptidoglycan
periplasm
space between the membranes. the peptidoglycan is submerged here, as well as the site for PMF since protons accumulate here
structure of gram negative outer membrane
lipid A has long fatty acid chains with sugar. frequently called endotoxin
core polysaccharide
o specific polysaccharide
archaeal cell walls
have an ether linked cytoplasmic membrane NO peptidoglycan NO outer membrane SOME contain pseudomurein beta 1,3 bonds instead of 1,4 not lysozyme sensitive no D amino acids not penicillin sensitive contain N-acetyl talosaminuromic acid
s layers
paracrystalline surface layer
protein or glycoprotein can self assemble. covers the entire cell surface
common in archaea functioning like a cell wall, resisting osmotic pressure
capsule/slime layer/extracellular polysaccharide
used for attachment to surfaces
EPS used in biofilm formation. this holds cells together and keeps them stuck to a surface, working as millions instead of one
provide protection from phagocytosis by immune cells
fimbriae
filament made of proteins relatively short abundant with thousands per cell easily fixed, stay and don't change important in surface adherence sticky and can bind
pili
filament made of proteins long fewer with 1-20 per cell retractable, extending in and out as needed do not rotate or swing
functions of pili
adherence, retraction allows the cell to pull itself closer to things
exchange of DNA through the process of conjugation
motility
twitching motility
utilizes type 4 pili
needs ability of attachment and retraction
important in pathogenesis
flagella and swimming motility
rotary filaments that spin the cell forward
polar flagella
only produced at the tips of the cell
amphitrichous flagella
found on both poles
lophotrichous flagella
only at one pole
peritrichous flagella
produced all over the cell
tumble
the cell rotates to a new random direction
unidirectional flagella
tumble one way, stop, and spin off in another direction by random chance
like a box
reversible flagella
tumble one way, stop, and go back the way they came
runs are straight lines back and forth
motor
made primarily of the basal body
driving force is in the cytoplasmic membrane
a rod extends through it, forming a flexible hook at the end where the filament is attached
filament is made of protein flagellum
turning driven by PMF
chemotaxis
can swim up or down gradients
is a biased random walk
can’t tell which way they’re going, but can sense concentrations of attraction
they swim in response to chemicals
capillary assay
bacteria is placed in a media like buffer. a capillary with a control, attractant, or repellent is place in it as well. the bacteria will react to this presence, swimming to or from it
phototaxis
bacteria swim to places containing more light, preferably with more pigment for better absorption
aerotaxis
swim towards high or low oxygen concentrations
gas vesicles
produced by aquatic phototrophs
little membrane sacs that accumulate gas that is trapped, giving buoyancy to keep suspension at high points in the water
