2. prokaryotic cell structure Flashcards
are prokaryotes bigger or smaller than eukaryotes?
smaller
how many chromosomes do prokaryotes have and what shape are most of the chromosomes?
one; circular
since prokaryotes do not have a nucleus, where are the chromosomes found?
nucleoid region
T/F: prokaryotes have membrane0bound organelles
false
T/F: prokaryotes have a more complex cell envelope than eukaryotes
true - made of membrane, cell wall and bacterial capsule
what process do prokaryotes use in order to reproduce?
binary fission
what was the first macro bacteria that was seen by the naked eye back in 1999?
thiomargarita namibiensis
this is where the DNA of bacteria is packaged without being surrounded by a membrane
nucleoid
how is DNA stabilized in the nuceloid region?
By the neutralization of the negative charge of the DNA by small polyamines (have +ve charge) and Mg2+ ions.
- histone like proteins (maintain DNA architecture and regulation DNA transactions such as replication, recombination/repair and transcription)
what are the TWO main functions of the prokaryotic cell envelope?
- protection - from hostile environments such as osmolarity, and harsh chemicals and antibiotics)
- pathogenicity - contribute to the invasiveness of pathogenic bacteria
list the three layers that make up the cell envelope
- cell membrane (all bacteria have cell membranes)
- cell wall (all bacteria except 1 species has a cell wall)
- the capsule (not all bacteria have capsules)
this is composed of a phospholipid bilayer and proteins including integral proteins which float in the bilayer and peripheral proteins that are associated on the inner membrane surface
cell membrane
these are lipid molecules that play a role in the fluidity of the membrane
hopanoids
when the temperature increases, the fluidity of the cell membrane also increases. therefore, more things can enter the bacteria. a result of this will be _____ (more/less) hopanoids produced to stabilize temperature
more
what are the functions of the cell membrane
- permeability and transport
- electron transport and oxidative phosphorylation
- excretion of hydrolytic exoenzymes and pathogenicity proteins
- biosynthetic functions
- chemotactic systems
this type of transport across the cell membrane relies on diffusion from high concentration to low concentration
passive transport
this type of passive transport requires NO energy or proteins
simple diffusion
this type of passive transport requires the use of channel proteins in order to transport molecules such as O2, CO2, H2O, and glycerol
facilitated diffusion
this type of transport across the cell membrane requires energy and transport proteins to travel from low concentration to high concentration
active transport
this type of transport across the cell membrane requires energy (ATP) to phosphorylate the molecule during the transport process and then use it in metabolism; use to uptake sugars by bacteria where the source of energy is from phosphoenolpyruvate (e.g. glucose and mannose)
group translocation
using specialized molecules such as siderophores to transport iron which is locked up in nature as Fe(OH)3, and insoluble and unavailable for transport
special transport processes
these are small molecular iron chelators that are produced by microbes and whose function is to sequester iron from the host and provide this essential metal nutrient to the microbe
siderophore
this function of the cell membrane is an analog function to the mitochondria function in eukaryotes
electron transport and oxidative phosphorylation
this function of the cell membrane contains six pathways of protein secretion, names type I - the VI secretion systems; used to secrete hydrolytic enzymes and pathogenicity toxins and other proteins
excretion of hydrolytic exoenzymes and pathgenicity proteins
this function of the cell membrane explains that the cell membrane is the site of the enzymes of phospholipids and cell wall biosynthesis
biosynthetic functions
this function of the cell membrane relates to the cell membrane having specific receptors that can bind to different kinds of attractants and repellants
chemotactic systems
this is a structural support that surrounds the cell in order to protect it. it
- gives shape to the cell and protects it from cell lysis
- protects the cell from toxic substances
- has components that contribute to the bacteria pathinogenicity
- is the site of action of several antibiotics
cell wall
what are the two different groups of bacteria based on their cell walls
gram-negative bacteria and gram-positive bacteria
do gram-negative or gram-postive bacteria have a thicker peptidoglycan sheet?
gram-positive
do gram-negative or gram-positive bacteria contain an outer membrane and a cell membrane
gram-negative
do gram-negative or gram-positive bacteria contain lipoteichoic acid and teicehoic acid
gram-positive
this portion of the cell wall is responsible for its strength
peptidoglycan layer
what are the three parts of the peptidoglycan layer?
- the backbone - consisting of alternating sugar derivatives NAG and NAM
- a set of identical tetra peptide side chains attached to NAM
- peptide cross-links or inter bridges
what are the two special components of gram-positive cell walls
- teichoic acids
- polysaccharides
these are partially responsible for the negative charge of the cell surface of gram-positive cell wall. they constitute major surface antigens of gram-positive bacteria
teichoic acids
what are the two different types of teichoic acids in gram-positive bacteria cell walls?
wall teichoic acids (WTA) and lipoteichoic acid (LTA)
in streptococcus pyogens (gram positive bacteria), what facilitates the attachment to host cells
LTA and M proteins
in some species, like those with gram-positive cell walls, sugars such as mannose, arabinose and glucuronic acid exist as subunits of _______ in the cell wall
polysaccharides
what are the special components of gram-negative cell walls
- outer membrane
- lipopolysaccharide
- porin channels
- lipoprotein
- the periplasmic space
this component of gram-negative cell walls is a bilayer structure. the outer edge contains lipopolysaccharides and channel proteins
outer membrane
this component of gram-negative cell walls consists of glycolipids (lipid A) and polysaccharides and it prevents the diffusion of hydrophobic materials (toxic compounds) through the outer membrane
lipopolysaccharide
this is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria
lipid A
this is attached to the core polysaccharide and extends from the core out into the environment. it consists of repeating oligosaccharide subunits made up of three to five sugars; it renders additional protection from the antimicrobial action of certain antibiotics
o antigen
this portion of the cell wall permits the passive diffusion of low molecular weight hydrophilic compounds, such as sugars, amino acids and certain ions
porin channels
large antibiotic molecules (such as beta lactams) have very ____ permeability therefore gram-negative bacteria have resistance to some antibiotics
low
this portion of the cell wall cross links the outer membrane and peptidoglycan layers to stabilize and anchor the outer membrane layer; it is the most abundant protein of gram-negative cells
lipoprotein
this is the space between the inner and outer membranes and the peptidoglycan layers
periplasmic space
if a gram-stained cell is stained purple what kind of bacteria is it?
gram positive
what are some examples of gram positive bacteria
bacillus, staphylococcus, streptococcus
if a gram-stained cell is stained red what type of bacteria is it
gram-negative
some bacteria such as mycobacteria tuberculosis have cell walls that contain large amounts of waxes called ____________. these cannot be stained with gram stains
mycolic acids
T/F; bacteria that contain cell walls with mycolic acids are resistant to antibiotics and many harsh chemicals including detergents and strong acids
true
this type of bacteria have no cell wall and contain no peptidoglycan. they are genetically closer to gram-positive bacteria; they are resistant to cell-wall inhibiting antibiotics (e.g. penicillins and cephlosporins)
mycoplasmas
this is an enzyme that attacks cell walls
- found in human secretions (tears, saliva and nasal secretions)
- break down the peptidoglycan backbone
lysozymes
T/F: the outer membrane of gram-negative cell walls prevents access to lysozyme therefore gram negative more resistant
true
this is an enzyme that attacks cell walls
- secreted by the bacteria itself to catalyze the degradation and turnover of peptidoglycan, to participate in cell wall growth and cell separation
- responsible for the dissolution of dead cells (autolysis)
autolysins hydrolytic enzymes
this is an enzyme that attacks cell walls
- these degrade bacterial cell walls and digest whole bacteria
( such as protozoa and the phagocytic cells of animals )
hydrolytic enzymes of higher organisms
this is an extracellular layer lying outside the cell, composed mainly of polymer of polusaccharides
capsule
how does the capsule contribute to the invasiveness of pathogenic bacteria?
- encapsulated bacteria are protected from phagocytosis
- the glycocalyx plays a role in the adherence of bacteria to the host cells (e.g. streptococcus mustans adhere tightly to the tooth surface by its glycocalyx trapping other bacterial cells of the same or different species which from the plaque on the tooth and then acid products are excreted by these bacteria causing dental caries)
how does the capsule contribute to the invasiveness of pathogenic bacteria?
- encapsulated bacteria are protected from phagocytosis
- the glycocalyx plays a role in the adherence of bacteria to the host cells (e.g. streptococcus mustans adhere tightly to the tooth surface by its glycocalyx trapping other bacterial cells of the same or different species which from the plaque on the tooth and then acid products are excreted by these bacteria causing dental caries)
