2. Prokaryotic Cell Structure Flashcards
Cocci
spheres
Diplococci
pairs
streptococci
chains
staphylococci
grape-like clusters
tetrads
4 cocci in a square
sarcinae
cubic configuration of 8 cocci
bacilli
rods
coccobacilli
very short rods
vibrios
resemble rods, comma shaped
spirilla
rigid helices
spirochetes
flexible helices
mycelium
network of long, multinucleate filaments
pleomorphic
organisms that are variable in shape
size-shape relationship
-important for nutrient uptake
-surface to volume ratio (S/V)
-large size and odd shape may be protective mechanisms from predation
bigger cell, bigger volume
surface: volume ratio decreases as cell gets better which increases nutrients
plasma membrane functions
encompasses the cytoplasm; absolute requirement for all living organisms
-selectively permeable barrier
-interacts with external environment
1. receptors for detection of and response to chemicals in surroundings
2. transport systems
3. metabolic processes
bacteria and eukaryotic cytoplasmic membrane
- ester linkage
- bilayer
- fatty acids
archaeal cytoplasmic membrane
- ether linkage
- either bilayer or monolayer
- phytanyl-isoprenes (NO FATTY ACIDS)
bacterial cell wall function
- maintains shape of the bacterium
- helps protect cell from osmotic lysis and toxic materials
- may contribute to pathogenicity
peptidoglycan (murein)
rigid structure lying just outside the cell plasma membrane
found in bacteria ONLY
pseudomurein is ONLY in archaea
gram positive
stain purple
thick peptidoglycan
gram negative
stain pink or red
thin peptidoglycan and outer membrane
peptidoglycan structure
-contains sugars + AA
-meshlike polymer of identical subunits forming long strands
two alternating sugars
-NAG: N-acetylglucosamine
-NAM: N-acetylmuramic acid
alternating D- and L- amino acids
RIDIG IN CELL WALL
Gram positive
Cell Wall
90% PG
10% techoic acids, lipotechoic acids
Gram negative
Cell Wall
-outer membrane
-LPS + lipid A
-phospholipid
-porin
10% peptidoglycan –> periplasmic space (between outer membrane and plasma membrane)
(Lipid A is a toxin, gram - contains endotoxins)
less sensitive to antibiotics
LPS -lipopolysaccharide layer
consists of three parts
1. lipid A
2. core polysaccharide
3. O side chain (O antigen)
Lipid A: buried in outer membrane
Core polysaccharide, O side chain: extend out from the cell
Archaeal Cell Walls
no peptidoglycan
pseudomurein (pseudopeptidoglycan)
-found in cell walls of certain methanogenic Archaea
-polysaccharide similar to peptidoglycan
-composed of NAG (N-acetylglucosamine) and N-acetyltalosaminuronic acid) , but no NAM (N-acetylmuramic acid)
beta-1,3 glycosidic bonds instead of beta- 1,4
CANNOT be destroyed by lysozyme and penicillin (due to these bonds)
Atypical Cell Walls
presence of mycolic acid (is waxy)
-mycobacterium
-nocardia
mycobacterium and nocardia are
acid fast organisms
they require an application of acid alcohol in order to penetrate the layer and stain
lack of a cell wall organisms:
mycoplasma
thermoplasma
mycoplasma
-group of pathogenic bacteria related to gram-positives
-completely lack a cell wall
-walking pneumonia caused by mycoplasma
thermoplasma
archaea
have tough cytoplasmic membranes (sterols or lipoglycans)
components outside of the cell wall
-capsules
-slime layers
-pili and fimbriae
-flagella
capsules
well organized and not easily removed from cell
usually composed of polysaccharides
visible in light microscope
protective advantages:
-resistant to phagocytosis
-protect from dessication
-exclude viruses and detergents
*more resistant to viral infection + control measures
*increases virulence - degree to which organisms can cause disease
slime layers
similar to capsules except diffuse, unorganized, and easily removed
slime may facilitate motility (prevent drying out)
fimbriae & pili
short, thin, hairlike, protein appendages
can mediate attachment to surfaces, motility, DNA uptake
sex pili
longer, thicker, less numerous
genes for formation on plasmids
required for conjugation (facilitation of genetic exchange between cells)
flagella
functions
-motility and swarming behavior
-attachment to surfaces
-may be virulence factors
monotrichous flagellation
one flagellum
lophotrichous flagellation
cluster of flagella at one or both ends
peritrichous flagellation
spread over entire surface of cell
motility
flagellar movement
swarming
spirochete motility
twitching and gliding motility
chemotaxis
chemotaxis
move toward chemical attractants such as nutrients, away from harmful substances
move in response to temperature, light, oxygen, osmotic pressure, and gravity
spirochete motility
-multiple flagella form axial fibril which winds around the cell
-flagella remain in periplasmic space inside outer sheath
-corkscrew shape exhibits flexing and spinning movements
storage inclusions
-storage of nutrients, metabolic end products, energy, building blocks
-glycogen storage
-carbon storage
-phosphate: polyphosphate
-amino acids: cyanophycin granules
ribosomes
complex protein/ RNA structures
-sites of protein synthesis
-bacteiral and archaea ribosome
the nucleoid
-usually not membrane bound (few exceptions)
-location of chromosome and associated proteins
-usually 1 closed circular, double-stranded DNA molecule= chromosome
-supercoiling and nucleoid proteins (different form histones) aid in folding
plasmids
extrachromosomal DNA
-usually small, closed circular DNA molecules
exist and replicate independently of chromosome
-episomes: may integrate into chromsome
-inherited during cell division
classification via mode of existence, spread, and function
