Lecture 7 Flashcards
true or false
bacteria are the smallest living cells
TRUE
0.1-10 micrometers
are bacteria prokaryotic cells or eukaryotic cells?
prokaryotic
nearly ALL bacteria have….
a rigid cell wall
what is the size of cell respiration in prokaryotes and in eukaryotes?
prokaryotes – the cell membrane
eukaryotes – the mitochondria
bacteria can be classified by which 6 things?
-appearance
-requirements for their growth
-their metabolism
-biochemistry
-antigenicity
-genotype
what do you mean that bacteria can be classified by their appearance?
their shape and their gram stain
what do you mean that bacteria can be classified based on the requirements for their growth?
the specific nutrients they need and can be selective on the media they grow in
what do you mean that bacteria can be classified based on their metabolism?
if they’re aerobic, anaerobic, or facultative (does aerobic if oxygen is present, but capable of switching to fermentation in absence of oxygen)
what do you mean that bacteria can be classified based on their biochemistry?
their proteases and enzymes
what do you mean that bacteria can be classified by their antigenicity?
by their recognition by the immune system
the cytoplasm of prokaryotes is rich in ____ ribosomes
70s
name the different shapes of bacteria
coccus (circular)
bacillus (rod shaped)
curved (coil/spiral)
OTHER – helical or club
name 4 FUNCTIONS of the bacterial cell wall
-maintains shape, strength, and rigidity
-protects against osmotic lysis
-allows for ATTACHMENT to (host) cells and to other surfaces
-provides PROTECTION against the immune system
explain the difference between the gram positive and the gram negative bacterial cell wall
gram positive: has THICK layer of peptidoglycan that serves as the cell wall. has plasma membrane inside.
gram negative: has outer and inner membrane. has thinner layer of peptidoglycan in the periplasmic space.
using GRAM STAIN is an easy way to determine what?
if the bacteria has a thick or thin cell wall. the stain stays in the THICK cell wall (cell wall)
name the 4 steps of using gram stain
- Crystal violet
- gram iodine
- decolorizer (alcohol or acetone)
- safranin red
when using the 4 step process of gram stain, what color will gram-positive be? what about gram negative?
gram positive — purple
gram negative – red
2 EXCEPTIONS
-some gram-positive bacteria are easily decolorized
-some gram-negative can retain the crystal violet color and appear somewhat gram positive
the CAPSULE of bacteria is also known as the __ layer
slime layer
what is the COMPOSITION of the capsule of bacteria?
polysaccharide or polypeptide
what is the term for the space between the 2 membranes of certain bacteria? which bacteria have this? what is it composed of?
space = periplasm
only in gram negative bacteria
composition = proteins and oligosaccharides in solution
what is the nucleoid? which bacteria have it?
nucleoid = DNA with associated RNA and proteins
both gram positive and gram negative bacteria have it
what are plasmids composed of?
DNA
Which bacteria have endospore?
NOT gram negative
gram positive can have it or not have it
an ENDOSPORE consists of….
all cell components + dipicolinate and special envelope components
true or false
gram positive bacteria does not have an outer membrane
TRUE
Which type of bacteria has a high lipid content?
explain
gram NEGATIVE
this is so because it has both an outer and inner membrane, and gram positive only has inner membrane
which is RESISTANT to cell wall disruption and WHY?
(gram positive or gram negative)
gram negative is resistant to cell wall disruption.
-has an outer membrane
which is relatively featureless? (has few proteins)
-gram positive or gram negative
gram positive – only has 1 membrane for proteins to be inserted into
explain the structure of a cell wall
composed of peptidoglycan.
has rigid glycan (polysaccharide; carbon based) chains that are crosslinked by flexible peptide bridges
which 2 classes of antibiotics inhibit bacterial cell wall synthesis?
penicillins and cephalosporins
which type of bacteria (gram positive or gram negative) has a feature that makes it resistant to antibiotics that breakdown the cell wall?
explain
gram negative
they have an outer membrane to protect the cell wall
LPS is part of which bacteria?
explain its structure
gram NEGATIVE
has CORE of polysaccharide
O side chain
Lipid A
what gives bacteria motility?
flagella
only _________ bacteria form spores
GRAM POSITIVE
What is the function of spores
to protect the bacteria. they are vegetative.
they have many layers
name 4 methods of bacterial metabolism
aerobic respiration
anaerobic respiration
glycolysis (fermentation)
pentose phosphate pathway (generates NADPH)
can aerobe bacteria ferment?
NO
What happens if anaerobes are exposed to O2?
they’re killed
what do anaerobes do in the absence of O2?
They ferment
explain what facultative bacteria can do in the presence and absence of oxygen
presence of oxygen – they respire
absence of oxygen – they ferment
what are “microaerophilic” bacteria?
they grow BEST at LOW O2
AND can grow without O2
give an example of a microaerophilic bacteria?
campylobacter jejuni
the metabolic end products of bacterial metabolism can be used to do what?
identify certain bacteria
what is facilitated diffusion?
does it require energy?
moving from high to low concentration with the help of a transmembrane protein
does NOT require energy
name 2 transport mechanisms of bacteria
facilitated diffusion and active transport
explain active transport
uses a gated pore.
once a particle binds to the protein gating the pore, it transports it in, using ATP and breaking it down into ADP and Pi
what is the function of secretion systems?
through use of secretion systems, bacteria can deliver their proteins and toxins to the interstitial fluid and into cells
which type of bacteria have secretion systems?
both gram positive and gram negative
as mentioned, both gram positive and gram negative bacteria have secretion systems.
is there any difference? if so, explain
YES
the secretion system is simpler in gram positive bacteria – only have ONE transmembrane protein (remember: gram positive only has 1 membrane while gram negative has 2)
how many and what are the names of the secretion systems in gram positive and in gram negative bacteria?
gram positive – 2 types
gram negative – 5 types
gram positive = Tat and Sec
gram negative = types 1-5
type I = direct transport
type II = 2-step process
type III = nanosyringe
type IV = nanosyringe
type V = 2 step process
in gram negative bacteria, which type(s) of secretion systems involve a chaperone protein?
types III and V
bacterial DNA is found in what configuration? what does this mean about bacterial replication?
bacterial DNA is a circular, double helix
therefore, to replicate the DNA must be unwound for the polymerase to come in and replicate the bacterial genome
where does bacterial DNA replication start and end?
starts at “origin of replication”, ends at “ter” region
once 2 forks are generated in bacterial DNA replication, they need to be unlinked by which enzyme? what happens if they’re not unlinked?
topoisomerase
if not unlinked, the bacterial cell will die
what can you say about the clinical aspects of topoisomerase
it is the target of many antibiotics (such as cipro).
targeting topoisomerase prevents bacterial DNA replication and thus causes it to die
true or false
in bacterial translation (mRNA–> protein) there is 1 ribosome for each mRNA transcript
FALSE
there are MANY ribosomes for a single mRNA transcript
How many steps are there in bacterial protein translation?
name them
initiation
elongation
peptidyl transferase
translocation
