chapter 3.2 cell structure/function (prokaryotes) Flashcards
wave light
amplitude of wave changes if color of light changes
limit of detection 0.2 nm
- bacteria is about 0.1-10 nm
- light bends around the bacteria if the wavelength doesn’t match size (can’t see it)
aka if bacteria is smaller than 0.2 nm, you won’t see it
gram pos colors
has color bc there’s more layers to hold onto the violet crystals, so alcohol won’t wash it away
gram neg colors
colorless
simple stain
one stain
differential stains
gram stain
bright field - uses light
phases and rings make light go in and out
dark field - phase contrast reverse
specimen is dark and back is light, no staining with fluorescent unless using fluorescent stain
atomic force
uses cantilever tip to “feel specimen”
confocal- light and fluorescent microscopy
- uses laser light to excite specimen
- uses coherent light for focused image
- can be put into 3D image
scanning
- coded with a molecule of gold (electron dense material)
- only 3D surface images gets reflected back
transmission
- passes through the image itself
- can see internal structures
- can see surface, but not 3D
cytoplasmic membrane
critical permeability barrier, separates inside from outside of cell
cell wall
rigid structure outside of cytoplasmic membrane, provides support and protection
ribosomes
small particles composed of protein and ribonucleic acid, responsible for synthesis of proteins
inclusions
aggregates of storage compounds containing C (starch), N, S, P
nucleoid
region of cell containing the DNA
chromosome
single circular DNA molecule
flagellum
long complex-protein filament used to propel bacteria through liquid media
6 basic morphologies
- coccus
- rod (bacillus)
- spirillum
- spirochete
- appendaged
- filamentous
average sizes
prokaryotes: 0.1-50 µm in diameter
eukaryotes: 2.0-200 µm in diameter
importance of “smallness”
- transport is a function of size
- surface to volume ratio decreases as size increases
gram pos cell envelope
- peptidoglycan
- simpler than gram neg membrane
gram neg
- periplasmic space
- periplasm is fluid around the cell
bacteria digestion
occurs outside cell with enzymes, then moves into cell envelope
smaller objects have larger surface area to volume ratio
smaller bacteria feed themselves easier
major chemical components of cytoplasmic membrane
- phospholipid bilayer
- integral membrane proteins
- membrane strengthening agents
-phospholipid linkages
phospholipid bilayer
- fatty acid
- glycerol
- phosphate
membrane strengthening agents
- sterols (eukaryotes and methanotrophs)
- hopanoids (bacteria)
warmer –> more sterols and hopanoids go in, fluidity level strong
phospholipid linkages -
bacterial and eukaryal phospholipids
form bilayers with glycerol component of the molecule bound to isoprene polymers (long chain hydrocarbon) via an ester linkage
phospholipid linkages -
archaeal phospholipids
form monolayer or bilayers with the glycerol component of the molecule bound to isoprene polymers via ether linkages
functions of cyto membrane
- permeability barrier
- protein anchor
- energy conservation
permeability barrier
- pores made out of proteins open and close protons
- protons can’t pass alone (uses channels)
- K will only be let in if there are high concentrations outside of the cell
- (+) charge goes in, (+) charge goes out to balance
protein anchor
- cells can concentrate proteins in one area
- proteins involved in DNA synthesis can be grouped in same location
energy conservation
- generated in cell from protons using protein channels
membrane transport systems
- simple transport
- group translocation
- ABC (ATP - binding cassette)
group translocation
- no glucose in cell bc it gets phosphorylated and normal glucose leaves the cell
- multiple proteins, molecule changes bc of phosphorylation
- phosphate blocks sugar from leaving cell
ABC transport
low concentrated thing can be brought in at the expense of ATP
types of simple transport
- uniporter
- antiporter
- symporter
group transport
the phosphotransferase system of E. coli
protein translocase systems
- proteins are transported via translocases
type 3 secretion system
- gram neg bacteria
- acts like syringe to inject secreted proteins into host cells
sec translocase system
comprised of 7 proteins including the YEG proteins which constitute the actual transporter
peptidoglycan cell wall (one huge molecule)
- unique to bacteria
- chemical structure: glycan tetrapeptide
glycan tetrapeptide
- N-acetylglucosamine (NAG)
- N-acetylmuramic acid (NAM)
- L-alanine
- D-alanine (not in euk)
- D-glutamic acid
- Lysine or diaminopimelic acid (DAP)
teichoic acids
- only gram pos
- acidic polysaccharides containing glycerol phosphate or ribitol phosphate groups
- imparts neg charge to gram pos bacteria, may be involved in transport of ions through the cell wall
β - lactam antibiotics
- All β related bc of similar structures
- Penicillin inhibits the transpeptidase reaction by interfering with the linkage of D-alanine residues
cell walls of archaea
- peptidoglycan is absent from archaea (replaced by S-layers and pseudomurein)
- S-layers are most common cell wall material for archaea
- Pseudomurein similar to peptidoglycan
S-layers
- paracrystalline structures composed of protein or glycoprotein subunits in some organisms in combination with polysaccharides
- when in combination with other structures, these for outermost portion
pseudomurein
- contains alternating repeats of N-acetylglucosamine and N- acetyltalosaminuronic acid
- false cell wall protein
Lipopolysaccharide (LPS) - Endotoxin
- pyrogen aka fever inducing
- found in gram neg
- located at outer portion of cell envelope
- outer leaf of lipid bilayer of gram neg
**chemical composition of LPS
- lipid A - anchor
- core polysaccharide
- o-specific side chain
porins
outer membrane associated, allows transport of small molecules
periplasmic space
- outer membrane of gram neg
- creates a perilasmic space between itself and the inner or cytoplasmic membrane
- outer membrane is permeable to small molecules BUT
- large molecules are not, so sequestered in periplasm (gel like from number of proteins)
arrangement of DNA
- 1 copy of DNA
- E. coli contains 4.6 million base pairs (4.6 x 10^3 kilobase pairs)
- supercoiling
supercoiling
- superimposition of a coil upon a coiled structure
- e. coli contains over 50 supercoiled domains
- supercoiling is stabilized by specific proteins
flagella structures
- filament: long helical tubular protein
- filament composed of flagellin, 10 – 20 µm in length
3 types of structure arrangement
- Peritrichous (originating around cell)
- Polar (originating at the end of cell)
- Iophotrichous (tuft at end of cell)
hook and basal body
- form a rotary motor driven by proton motive force (1000 protons per revolution)
- basal body: (4 elements in gram neg, 2 elements in gram pos)
chemotaxis/phototaxis
- runs and tumbles (twiddles)
- random biased walk
- chemoreceptors
- chemoattractant/chemorepellent (not spacial, temporal instead)
- scotophobotaxis/phototaxis
runs
flagellum moves one way, wound together, this is how e. coli moves
tumbles
unwinds, flagellum working against each other to stay still; reorients and then runs again
longer run
- more glucose
- when in the gradient
- stops running when it reaches highest concentration, consumes glucose, starts again
chemoreceptors
- fla
- fli
- flg
scotophobotaxis
moves towards light, repelled by darkness
phototaxis
directed towards light
aerotaxis
towards O2
osmotaxis
towards salt
magnetotaxis
migrates in magnetic field
fimbriae
tubular protein structures on outer portion of cell envelope
(shorter and thinner than flagella, often covers cell)
- help stick bacteria to surfaces (like bacterial fur)
pili
structurally similar to fimbriae, but longer and fewer in number; produced as and when needed and are lost when not required (like whiskers)
- sex pilus like fishing rod
capsules and slime layers:
the glycocalyx
- polysaccharide containing material lying outside the cell (polysaccharides, glycoproteins and glycolipids)
- serve to protect against phagocytosis desiccation, chemical attack, physical disruption
- maintains structure and function of biofilm
capsule
tight matrix that excludes india ink
slime layer
easily deformed does not exclude india ink
carbon storage polymers
- Poly–hydroxybutyric acid (PHB)
- Class of Lipid-like compounds formed from β-hydroxybutyric acid units C4 – C18
- glycogen
gas vesicles
small gas-filled structures made of protein that confer buoyancy to cells
endospore/vegetative cells
- bacillus and clostridium (soil bacteria)
- only produced by bacteria
- differentiated cells highly resistant to heat, chemicals, and radiation
endospore structure
- Exosporium – outer protein coat
- Spore Coat – layers of protein
- Cortex – loose peptidoglycan
- Core – cell wall, cytoplasmic membrane, cytoplasm, nucleoid, etc.
properties of the core
- Dipicolinic acid
- Highly dehydrated (10 – 30 % of vegetative cell)
- Small Acid Soluble Spore Proteins (SASPs) protect DNA and provide source of food for outgrowth
endospore formation (sporulation)
- Stimulated by lack of nutrients
- Cellular differentiation involves 200 genes in B. subtilis
- Most resistant biological structure
germination (outgrowth)
- Loss of dipicolinic acid
- Metabolism of SASPs
- Production of DNA, RNA, proteins
- Uptake of water and swelling
- Broken spore coat
