functional anatomy of the prokaryotic cell Flashcards
what is the cell envelope
the plasma membrane and all layers external to it
what does glycocalyx mean
sugar coat
where is the glycocalyx
part of the cell envelope, exterior to the cell wall
what is the glycocalyx in terms of composition
a network of polysaccharides
what are the two types of glycocalyx
capsules and slime layers
when is the glycocalyx considered a capsule
when it is well organized and not easily washed off
when is the glycocalyx considered a slime layer
when it’s unorganized and loosely attached to the cell wall
what part of the cell is the glycocalyx attached to
the cell wall
where is the glycocalyx made
inside the cell
from being made inside the cell, how does the glycocalyx get outside of the cell
it’s secreted to the surface
T or F: all bacteria have a glycocalyx
false; not all of them do
T or F: for the bacteria that have a glycocalyx, the chemical structure is the same across species
false; the chemical structure will vary across species
describe the advantages of having a glycocalyx
they help bacteria resist phagocytosis b/c they’re slippery, they aid in attachment to surfaces, prevent desiccation b/c the layer contains lots of water, they inhibit entry to bacterial viruses or other hydrophobic toxic materials
what is the S layer
another layer of the envelope that may be present
what is the S layer attached to
the outermost portion of the cell wall
what does S stand for in S layer
surface
what is the S layer made up of
protein or glycoprotein
what are the functions of the S layer
protection against predacious bacteria/ion and pH fluctuations, or osmotic stress. Promotes adhesion to surfaces, helps maintain shape and rigidity, protects some pathogens against host defenses
T or F: bacteria can have both a glycocalyx and the S layer
true
T or F: all bacteria have a cell wall
true; except for a few instances
what are the major functions of the cell wall
protection against osmotic lysis, provides shape, protects against entry of toxic materials
is the cell wall external or internal to the glycocalyx and S layer
internal
what is the cell wall made up of
peptidoglycan
T or F: peptidoglycan is a polymer
true
how many subunits does peptidoglycan have
2
what type of subunits does peptidoglycan have
monomer subunits
what are the two monomer subunits of peptidoglycan
N-acetylglucosamine and N-acetylmuramic acid
how do the NAM and NAG arrange themselves in peptidoglycan
they form a backbone of 10-65 rows
are NAM and NAG the only components of the peptidoglycan backbone?
no, there are also tetrapeptides (peptide made up of 4 amino acids)
what are tetrapeptides
peptides made up of 4 amino acids
what do the tetrapeptides do in the peptidoglycan backbone
they crosslink strands of the backbone together
what is the shape of the NAM-NAG strands in peptidoglycan
helical
T or F: tetrapeptides can attach to both NAM and NAG
false; they only attach to NAM
which do tetrapeptides attach to: NAM or NAG?
NAM only
name the two ways in which crosslinking of the peptidoglycan can occur
direct linkage
peptide interbridge
describe direct linkage of the peptidoglycan backbone
a peptide bond is formed between the two tetrapeptides
describe a peptide interbridge of the peptidoglycan backbone
a peptide bridge attached to each tetrapeptide (ie a string of glycines will connect them)
which type of bacteria favors direct linkage of the peptidoglycan backbone
gram negative
which type of bacteria favors peptide interbridge of the peptidoglycan backbone
gram positive
how does penicillin affect peptidoglycan
it inhibits the enzymes involved in cross linking
which bacteria takes more of a hit from penicillin preventing crosslinking of the peptidoglycan backbone
gram positive
T or F: the amino acids in the tetrapeptide of peptidoglycan are always the same
false; they can vary
T or F: the order of amino acids in the tetrapeptide of peptidoglycan is always the same
false; the order can vary
T or F: the position of the bridge connecting tetrapeptides in peptidoglycans can vary
true
T or F: the composition of the peptide interbridge of peptidoglycan can vary
true
what types of amino acids make up the tetrapeptide
alternating D and L forms
which do humans use to make up our proteins: D or L amino acids
L amino acids
why would D amino acids be advantageous for bacteria to use to form their cell wall
presence of D amino acids protects against attack by most peptidases, which only recognize L isomers
T or F: peptidoglycan is strong
true; due to NAM-NAG backbone
T or F: peptidoglycan is flexible
true; due to crosslinks
T or F: peptidoglycan is porous
true
which domain is peptidoglycan found in
Domain bacteria
T or F: peptidoglycan can be found in organisms not belonging to Domain Bacteria
false; it’s only found in Domain Bacteria
describe the cell wall structure in a gram pos bacteria
a thick layer of peptidoglycan with lots of cross links
what are teichoic acids
a polymer of an alcohol (glycerol or ribitol) linked by phosphate groups
what type of charge do teichoic acids have
negative
where are teichoic acids located in gram pos bacteria
within the cell walls
what are the two types of teichoic acids
wall teichoic acids
lipoteichoic acids
describe wall teichoic acids
they’re bound covalently to peptidoglycan (NAM)
are wall teichoic acids bound to NAM or NAG
NAM
describe lipoteichoic acids
they’re bound to lipids that are present in the PM
describe the functions of teichoic acids
help maintain cell envelope structure, involved in binding pathogenic species to host tissues, and they protect bacteria from harmful substances
T or F: in gram pos bacteria, some proteins may associate with the peptidoglycan layer
true; they may be involved in adhesion or virulence
describe the cell wall structure of a gram neg bacteria
a thin layer of peptidoglycan and an outer membrane
what is the outer membrane composed of
a phospholipid bilayer consisting of phospholipids, lipoproteins, and lipopolysaccharides
describe the structure of a phospholipid
phosphate, glycerol, and two fatty acids
what do lipoproteins do
link the outer membrane to the peptidoglycan in gram neg bacteria
what is the most abundant lipoprotein in gram neg bacteria
Braun’s lipoprotein
describe the basic structure of lipopolysaccharides (LPS)
3 parts: lipid A, core polysaccharide, and the O side chain
how many sugars and phosphates make up the core polysaccharide in an LPS
10
T or F: the O side chain is always the same in an LPS
false; it will differ between strains
how does the gram neg bacteria get it’s negative charge
lipopolysaccharide gives it the neg charge
what part of an LPS is embedded in the membrane
lipid A
which part of an LPS is toxic
lipid A
what is another name for lipid A in LPS since it’s toxic
Endotoxin
describe how lipid A of LPS is toxic
sometimes the endotoxin can be released into the blood and cause shock when you have a bacterial infection
functions of LPS in gram neg bacteria?
stabilizes outer membrane via lipid A, protects the cell by acting as a permeability layer, protects pathogenic species from host defenses (bacteria will change the makeup of O so the host antibodies don’t work)
how many membranes do gram neg bacteria have
2
what additional membrane does a gram neg have
an outer membrane
what is embedded in the outer membrane of gram neg bacteria
porins
what are porins
they form a channel that spans the outer membrane and allows small molecules to pass through
how can peptidoglycan be destroyed
by penicillin or lysozyme
describe how penicillin and lysozyme can break down peptidoglycan
lysozyme breaks NAM-NAG bonds = osmotic lysis
penicillin and lysozyme cause bacteria to lyse in a hypotonic environment
describe peptidoglycan in a hypotonic environment with penicillin and lysozyme
lysozyme digests wall (breaks NAM-NAG bonds), water enters, lysis happens
will a bacteria lyse in an isotonic environment?
no
describe a gram pos bacteria in an isotonic environment and why it will not lyse
when treated with penicillin and lysozyme, the cell wall will be lost and the cell becomes a protoplast and remains intact
what is a protoplast
a gram pos organism that has lost its cell wall
describe a gram neg bacteria in an isotonic environment
peptidoglycan layer is lost but the outer membrane remains = spheroplast
what is a spheroplast
gram neg bacteria that have lost the peptidoglycan layer but still contain the outer membrane
which bacteria are more sensitive to penicillin and lysozyme + why
gram pos because they don’t have that protective outer membrane
describe the gram stain: addition of primary stain
crystal violet enters the cytoplasm and colours both groups of bacteria purple
describe the gram stain: addition of iodine
iodine acts as a mordant and forms large crystals with the stain. this now becomes too large to escape through the cell wall
describe the gram stain: decolorizer
gram pos: alcohol dehydrates the peptidoglycan layer so it’s impermeable to the iodine-CV complex = purple is trapped
gram neg: alcohol dissolves lipids of outer membrane, iodine-CV complex can escape = purple leaves
describe the gram stain: addition of counterstain
safranin is added so gram negative organisms will stain red, gram positive will remain purple
T or F: some gram pos organisms can give a gram neg response (in regards to gram stain)
true
when will gram pos organisms give a gram neg repsonce in regards to a gram stain
when the cells are dead
describe what it means to be gram variable
as the culture ages, more and more cells will look gram negative
describe how members of the Genus Mycoplasma have an atypical cell wall
no cell wall and are only surrounded by a PM. To protect against lysis, many have cholesterol in the PM
describe how members of Phylum Chlamydiae and Phylum Plantomycetes have atypical cell walls
they have a cell wall that contains only an outer membrane (no layer of peptidoglycan)
what is the periplasmic space
region between the cell wall and the PM
which type of bacteria (gram pos or neg) has a large volume
gram neg has a large periplasmic space
what is the name for the substance occupying the periplasmic space
the periplasm
what does the periplasm contain inside of it
various types of proteins
describe the protein types located in the periplasm
hydrolytic enzymes, transport proteins, proteins involved in making peptidoglycan, proteins involved in detoxifying harmful compounds
T or F: bacterial plasma membranes contain sterols
false; they do not contain sterols like animal membranes do
instead of sterols, what do bacterial PMs have
sterol-like molecules called hopanoids
define hopanoid
a sterol-like molecule that is located in a bacterial PM
function of a hopanoid?
help stabilize the membrane
what two types of proteins does the PM contain
peripheral and integral
what do peripheral proteins do
act as enzymes and provide support for the membrane
what do integral proteins do
they transport materials and are involved in energy conservation
list some functions of the PM
selectively permeable, site of cell resp (ETC), site of photosynthesis (photosystems), site of lipid synthesis and cell wall components, contains receptor molecules
what major structures are located in the cytoplasm
nucleoid, ribosomes, and inclusions
what are the three cytoskeletal elements in EUKARYOTES
microfilaments, microtubules, intermediate filaments
describe the BACTERIAL cytoskeleton
contains homologues of all three types of eukaryotic proteins (MTs, MFs, IFs) + they contain unique proteins that aren’t in eukaryotes
what are the functions of the unique proteins found in the bacterial cytoskeleton
aid in cell division, help localize proteins to specific sites within the cell, they help determine cell shape
what is a nucleoid
irregularly shaped region where the DNA is found
T or F: the nucleoid has a membrane
false; it has no membrane, so it’s only a region of the cell
describe the structure of prokaryotic DNA
a single, double-stranded, helical, circular DNA molecule
what is the single, double-stranded, helical, circular DNA molecule called in bacteria
bacterial chromosome
what proteins are in the nucleoid that aid in packaging DNA
nucleoid associated proteins (NAPS) (ie the HU protein)
what are plasmids
extrachromosomal DNA
where are plasmids located
in the cytoplasm
T or F: plasmids exist independently of the bacterial chromosome
true
what shapes can a plasmid be
linear or circular
T or F: plasmids are required for survival
false; but they can give a specific advantage
ribosomes are the site of __ ___
protein synthesis
where in the cell are ribosomes located
within the cytoplasm or loosely attached to the PM
what are ribosomes in prokaryotes denoted as
70S
what does S stand for in 70S
Svedberg unit
what is a svedberg unit
a unit of measurement that measures the relative rate of sedimentation during ultra-high speed centrifugation. It’s a function of the size, weight, and shape of the subunits
describe what makes up the 70S ribosome
30S subunit and the 50S subunit
what are ribosomes made up of (hint: what molecules)
rRNA and protein
T or F: some organisms in Bacteria and Archaea have internal membranous structures
true
describe the intracytoplasmic membranes of cyanobacteria
they carry out photosynthetic reactions, so they have internal membranes called thylakoids
other than cyanobacteria, which organism has intracytoplasmic membranes
nitrifying bacteria (soil organisms that convert nitrogen compounds into forms usable by green plants)
what is the main function of intracytoplasmic membranes
increase surface area to carry out metabolic activities
what are inclusions
aggregates of organic or inorganic substances
where are inclusions located
cytoplasm
what form can inclusions be
granules, crystals, globules
T or F: inclusions are visible with the light microscope
true
describe membranes of inclusions
inclusions can be membrane-bound or free in the cytoplasm
T or F: some inclusions may be found in invaginations of the PM
true
what are 3 types of storage inclusions
carbonosome, polyphosphate granule, sulfur globule
what do carbonosomes do
store carbon
what do the most common type of carbonosomes contain
PHB
what do polyphosphate granules do
store phosphate
what do sulfur globules do
store sulfur
what are magnetosomes
inclusions of iron oxide
structure of magnetosomes
linear
location of magnetosomes
underneath the PM, found in aquatic bacteria
function of magnetosomes
allow bacteria to orient themselves with respect to the earth’s magnetic field (ie know which way is up)
T or F: a gas vacuole is surrounded by a membrane
false; it has no membrane
which bacteria have gas vacuoles
aquatic bacteria (that are generally photosynthetic)
how is a gas vacuole formed
formed from many small, hollow, cylindrical structures called gas vesicles
T or F: gas vacuoles are impermeable to water
true
T or F: gas vacuoles are impermeable to atmospheric gases
false; they are freely permeable to atmospheric gases
function of gas vacuoles?
they allow bacteria to regulate their buoyancy so they can get optimal light, oxygen, and nutrients
what are microcompartments (ie structure, orientation)
large polyhedrons made up of a protein shell. They encompass enzymes
example of a microcompartment?
carboxysome
which organisms are carboxysomes found in
cyanobacteria
function of carboxysomes in cyanobacteria?
contain the enzymes required for CO2 fixation (ie the dark phase of photosynthesis)
