Chapter Two Flashcards
Cell envelope:
Structure that surrounds the cytoplasm of prokaryotes.
Cell membrane, Cell wall, Appendages attach/integral to envelope
Monomorphic:
Single-shaped, most bacteria are monomorphic.
ex.) antibiotic-resistant Staphylococcus aureus
Pleomorphic:
Many shapes, a few bacteria are pleomorphic.
ex.) Helicobacter pylori
Peptidoglycan:
Peptidoglycan is a rigid envelope surrounding the cytoplasmic membrane of most bacterial species.
Major component of the cell wall in bacteria.
It helps protect bacterial cells from environmental stress and helps preserve cell morphology throughout their life cycle. Peptidoglycan biosynthesis is also an important regulator of bacterial cell division.
Murein and its composition:
Unique to bacteria, a target for antibiotics.
ex.) B-lactams (Penicillin) inhibit synthesis.
Lipopolysaccharides, sugar part is made of N-acetylglucosamine and N-acetylmuramic acid units
Periplasm:
Aqueous space between the inner and outer membrane.
Secreted proteins (like B-lactamase and other enzymes).
What are the things that protect the cell membrane?
Gram-positive, gram-negative, acid-fast, mycoplasma (none).
Gram-positives:
Thick cell wall (thick peptidoglycan)
Teichoic acid and Lipoteichoic acid.
What are teichoic acids (Gram-positive Cells)?
– Lipoteichoic acid links to the plasma membrane
– Wall teichoic acid links to peptidoglycan
- May regulate movement of cations
- Provide antigenic variation
- Pathogenesis- Adherence
- Rigidity
Gram-negatives:
Thin cell wall, out membrane with LPS (hydrophilic)- hydrophobic barrier.
Periplasm, LPS and endotoxin, porin.
Gram-negative cell wall:
Outer membrane is chemically distinct from all other biological membranes, resistant to harmful chemicals, inner part regular phospholipids, outer part has Lipopolysaccharides (LPS), Lipid A is an endotoxin.
- Outer membrane makes the cell wall less permeable.
- Porins permit the diffusion of hydrophilic compounds.
- Transport systems – special proteins for
larger hydrophilic compounds. - Periplasm: Aqueous space between the
inner and outer membrane - Contains murein and gel-like solution of cell wall precursors and proteins that assist in nutrition
- Concentrate valuable enzymes
Periplasm:
In gram-negatives, the aqueous space between the inner and outer membrane.
Acid-fast cells:
Waxes (mycolic acids- branched hydrocarbons, 60-90 carbons long).
Archaea cell walls:
Many have no cell wall, they have an S-layer, which are glycoproteins. They have a special cell membrane: isoprenoid-containing, bilayer, long monolayer.
Shape of prokaryotic cells
Bacillus:
Coccus:
Spiral:
Bacillus: rod-shaped
Coccus: spherical-shaped
Spiral: vibrio, spirillum, spirochete
Arrangement of prokaryotic cells
Pairs:
Clusters:
Chains:
Groups of four:
Cubelike groups of eight:
Pairs: diplococci, diplobacilli
Clusters: staphylococci
Chains: streptococci, streptobacilli
Groups of four: tetrads
Cubelike groups of eight: sarcinae
Shapes and arrangements of bacterial cells:
Morphology’s link to properties of prokaryotic cells:
typically does not predict
physiology, ecology, phylogeny, or other
properties of a prokaryotic cell.
Selective forces involved in setting the morphology:
- Optimization for nutrient uptake (small cells and high surface-to-volume ratio, like appendaged cells).
- Swimming motility in viscous environments or near surfaces (helical or spiral-shaped cells).
- Gliding motility (filamentous bacteria).
What are the units used when visualizing prokaryotic cells?
Measured using the metric system
1 micrometer (µm) = 10^-6 m
1 nanometer (nm) = 10^-9 m
Microscopy resolution:
The ability of the lenses to distinguish fine detail and structure.
White light- Resolution: 0.2 µm
Shorter wavelengths of light provide greater resolution.
A microscope with a resolving power of 0.2μm can distinguish between two points ≥ 0.2 μm apart.
Microscopy refractive index:
Measures the light-bending ability of a medium.
Specimen’s refractive index must be different from the medium.
What are the four types of microscopy and when would each be used? What resolution is used for each?
Light microscopy: Uses light to observe specimens. Stains, fluorescent stains. Uses 0.2 microns resolution.
Electron microscopy (TEM and SEM resolution):
TEM: extremely high resolving power, visualize internal structures of the cell, 10,000–10,000,000X; resolution 0.01 nm
SEM: Less resolving power than TEM, but examines intact surfaces. 1,000–500,000X; resolution 10 nm
Scanning Probe Microscopy: Studying surfaces at the nanoscale level.
What is the Compound Light Microscope used for in Brightfield microscopy, and describe the parts (11 parts).
