Chapter 3 Flashcards
what does the small cell size do for prokarytic cells?
high surface area to low volume
* Facilitates rapid uptake of nutrients, excretion of wastes
* Allows rapid growth
what are the disadvantages of Prokaryotic cells
vulnerability to threats including
predators, parasites, and competitors
what does the large size of Eukaryotic cells do for it
many cellular processes take
place in membrane-bound compartments
(visible light) can magnify 1,000x
Common, important tool in microbiology
Light microscope
can magnify more than 100,000x
fine details
Electron microscope
can produce images of individual atoms on a surface
Atomic force microscope
Light passes through specimen and then series of
magnifying lenses
is most common type of microscope
Evenly illuminates the filed of view and generates a bright
background
Bright-field microscope
a selection of lens options provides different magnifications. the total magnification is the product of the magnifying power of the ocular lens and the what lens
objective lens
controls the brightness of the light
rheostat
controls the amount of light that enters the objective lens
iris diaphragm lever
focuses the light
condenser lens
magnifies the image, usually 10-fold (10x)
ocular lens (eye piece)
apparent increase in size
Magnification
two types of lens in modern compound microscopes
objective
microscope objective lens powers
4x, 10x, 40x, and 100x
magnification power of ocular lens
10x
between light source and specimen
Condenser lens
focuses light on specimen, does not magnify
Condenser lens
resolving power, or ability to distinguish two objects that are very close together
Resolution
minimum distance between two points at which those points can be observed as separate
Resolution
what does resolution depend on
quality and type of lens, wavelength of light
magnification
specimen preparation
Maximum resolving power of light microscope is
0.2 micrometer
what is used for maximum resolution?
immersion oil
is used to displace air
between lens and specimen when using high powered 100x
objective
immersion oil
measure of speed of light passing
through medium
refractive index
bending of light ray
refraction
Refractive index of glass is different from what but similar to what
different from air but similar to oil
determines how easily cells can be seen
Contrast
do stains kill microbes?
yes
- Cells appear bright against a dark background
- Directs light toward specimen at angle
- Only light scattered by specimen enters objective lens
Dark-Field Microscope
- Special optics amplify difference between refractive
index of dense material and surrounding medium - Makes cells and other dense material appear darker
Phase-Contrast Microscope
- Like phase-contrast, has special optics that depend
upon differences in refractive index - Separates light into two beams that pass through
specimen and recombine - Light waves are out of
phase when recombined,
yield three-dimensional
appearance of image
Differential Interference Contrast (DIC) Microscope
- Cells or materials either naturally fluorescent or tagged
with fluorescent dyes - Molecules absorb light at one wavelength (usually
ultraviolet light) and emit light at longer wavelength
Fluorescence Microscopes
UV light projected onto, not
through, specimen
epifluorescent
- Allows detailed interior views of intact cells
- May provide 3-D images of thick cells
- Specimens usually stained with fluorescent dye
- Fluorescent tags bind to certain internal compounds
- Marks their location
Scanning Laser Microscopes (SLM)
- Uses a laser beam to illuminate a point
- Mirrors scan laser beam across specimen, illuminating
successive planes
– Each plane represents one fine slice of specimen; Computer
constructs 3-D image
– Like a miniature computerized axial tomography (CAT) scan
for cells
Confocal Microscopes
- low energy used
- Less damaging to cells; allows time-lapse images
- Give interior views of relatively thick structures
Two-photon Microscope
- Can magnify images 100,000x
- One drawback is that lenses and specimen must be in vacuum
- Air molecules would interfere with electrons
- Results in large, expensive
unit and complex specimen
preparation
Electron microscopy
wavelength of electrons
~1,000 shorter than light
* Resolving power ~1,000-fold
greater: ~0.3 nm
two types of Electron microscopy
Scanning Electron Microscope (SEM)
Transmission Electron
Microscope (TEM)
- Beam of electrons pass through or scatter
- Depends on density of region: dark areas dense
- Thin-sectioning used to view fine
internal details, but process can
distort cells
Transmission Electron
Microscope (TEM)
- Used to observe surface details
- Surface coated with thin film of metal
- Beam of electrons is scanned over surface
- Electrons released from specimen are observed
- Yields 3-D effect
Scanning Electron Microscope (SEM)
types of Scanning Probe Microscopes
Atomic Force Microscopes (AFM)
- Detailed images of surfaces
- Resolving power much greater than that of EM
- Avoid special preparation required for EM
- Sharp probe moves across
sample’s surface - Feels bumps, valleys of atoms
- Laser measures motion,
computer produces surface map
Atomic Force Microscopes (AFM)
uses a drop of liquid specimen
Wet mount
downsides of wet mount
can be difficult to see when colorless
what kind of cells are in wet mount
Live cells
drying and fixing specimen before staining to visualize
smear
involves one dye
Simple staining
what kind of dyes carry positive charge
Basic
what kinds of dyes carry negative charge and can be used
on wet mounts
Acidic dyes
used to distinguish different
types of bacteria
Differential staining
types of Differential staining
Gram stain
Acid-fast staining
most common stain for bacteria
Gram stain
Two groups of Gram stain
Gram-positive, Gram-negative
what color does violet and iodine turn the cells
purple
what color does alcohol turn the cells
gram-positive = purple
gram-negative = colorless
what color does safranin turn the cells
gram-positive = purple
gram-negative = pink
used to detect organisms that do not readily take up dyes
Acid-fast staining
special stains
capsule stain
endospore stain
flagella stain
a staining procedure used to detect specific cell structures
special stains
- Some microbes surrounded by gel-like layer (for protection)
- Stains poorly, so negative stain often used
- India ink added to wet mount is common method
Capsule stain
- Members of genera including Bacillus, Clostridium
form resistant, dormant endospore - Resists Gram stain, often appears as clear object
- Endospore stain uses heat to facilitate uptake of the
primary dye malachite green by endospore - Counterstain (usually safranin) used to visualize other cells
Endospore stain
- Too thin to be seen with light microscope
- coats flagella to thicken and make visible
- Presence and distribution can help in identification
Flagella stain
uses fluorescent dye attached
to an antibody to tag unique microbe protein
Immunofluorescence
two most common Prokaryotic Cell’s shapes
Coccus
Rod
spherical
Coccus
cylindrical
Rod
other prokaryotic cell’s shapes
Vibrio
spirillum
spirochete
Pleomorphic
shapes of bacteria
Coccus
Bacillus
Vibrio
Spirillum
Spirochete
Pleomorphic
Spherical cells, may be flattened
on one end or slightly oval.
coccus
A rod shaped, cylindrical cell
Bacillus
A short, curved rod.
vibrio
A curved rod long enough to
form spirals.
spirillum
- form swarms of cells that glide over moist
surfaces as a pack - Collectively release enzymes and degrade organic
material, including other bacterial cells
Myxobacteria
A long, spiral-shaped
cell with a flexible cell wall and a unique mechanism of
motility.
Spirochete
Refers to bacteria that characteristically
vary in their shape.
Pleomorphic
Most prokaryotes divide by what
binary fission
type of cell groupings
chains
packets
clusters
cell divides in one plane
chains
cells divides in two or more planes perpendicular to each other
packets
defines boundary of cell
Cytoplasmic membrane
Hydrophobic tails face where
in
hydrophilic heads faces where
out
Proteins serve numerous functions
- Selective gates
- Sensors of environmental conditions
- Fluid mosaic mode
proteins drift about in lipid bilayer
Fluid mosaic model
have same general structure of
cytoplasmic membranes
Bacteria and Archaea
is selectively permeable
Cytoplasmic membrane
what passes freely through Cytoplasmic membrane
O2, CO2, N2, small hydrophobic molecules
Other molecules must be moved across membrane via
transport systems
Free movement of molecules in and out of the cell through the phospholipid bilayer
Simple Diffusion
what is the movement for simple diffusiom
high to low concentration
Diffusion of water across
selectively permeable
membrane due to
unequal solute
concentrations
osmosis
a solution with a high concentration of solutes relative to water, or to a state of having too much muscle tone.
Hypertonic
as a lower concentration of solute than another solution, meaning water will flow out of it
Hypotonic
having the same concentration of water and solutes as a cell
isotonic
a series of protein complex embedded in the cytoplasmic membrane
Electron Transport Chain
Use energy from electrons to move protons out of cell
Electron Transport Chain
energy that Electron Transport Chain uses
proton motive force
to move nutrients and other small
molecules across the cytoplasmic membrane
transport systems
things that transport systems use
Transporters, permeases or carriers
move waste products and other toxic substances out of cell
efflux pumps
is a form of passive transport
Facilitated diffusion
how does Facilitated diffusion move
Movement down gradient; no energy required
requires energy
Active transport
what movement does Active transport do
Movement against gradient
two mechanisms of Active transport
- proton motive force
- Use ATP (ABC transporter)
Chemically alter compound
Group Translocation
examples of Group Translocation
Glucose
active movement out of cell
Protein secretion
example of Protein secretion
exoenzymes
(extracellular enzymes)
exoenzymes
Proteins tagged for secretion via
signal sequence
is strong, rigid
structure that prevents cell
lysis
Cell wall
two main types of bacteria
- Gram-positive
- Gram-negative
color of gram staining for Gram-positive
purple
color of gram staining for Gram-negative
pink
types of gram positive
bacillus
staphyloccoccus
streptococcus
types of gram-negative
escherichia, neisseria, pseudomonas
has porin proteins
gram negative
Cell wall is made from
peptidoglycan
Alternating series of subunits
form
glycan chains
types of glycan chains
N-acetylmuramic acid (NAM)
* N-acetylglucosamine (NAG)
string of
four amino acids
Tetrapeptide chain
links glycan
chains
Tetrapeptide chain
Tetrapeptide chain links glycan
chains in gram-negative
Direct link
Tetrapeptide chain links glycan
chains in gram-positive
Peptide interbridge
has thick peptidoglycan layer
The Gram-Positive Cell Wall
lies below peptidoglycan layer
periplasm
has thin peptidoglycan layer
Gram-negative
cell wall
what is unique about Gram-negative cell wall
outer membrane
what is Gram-Negative Cell Wall outermembrane made from
Bilayer made from lipopolysaccharide (LPS)
how are Gram-Negative Cell important medically
signals immune system of invasion
by Gram-negative bacteria
another name for lipopolysaccharide (LPS)
endotoxin
blocks passage of many molecules including certain antibiotics
Outer membrane
Small molecules and ions can cross via
porins
Between cytoplasmic membrane and outer membrane is
periplasmic space
what is Periplasm filled with and why
proteins because exported proteins
accumulate unless specifically moved across outer
membrane
Can weaken to point where unable to prevent cell lysis
Peptidoglycan
interferes with peptidoglycan synthesis by Preventing cross-linking of adjacent glycan chains
Penicillin
is Penicillin more effective against Gram-positive bacteria or
Gram-negative bacteria
Gram-positive
breaks bonds linking glycan chain by Destroying structural integrity of peptidoglycan molecule
Lysozyme
is Lysozyme more effective against Gram-positive bacteria or
Gram-negative bacteria
Gram-positive
have a thick peptidoglycan layer as their primary cell wall component
gram-positive bacteria
have a thin peptidoglycan layer covered by an additional outer membrane, making them more resistant to antibiotics due to this extra barrier
gram-negative bacteria
do notes on graph on slide 59
bacteria that lack a cell wall
Mycoplasma
Penicillin
Lysozyme
have variety of cell walls
Archaea
have variety of cell walls
Archaea
do Archaea have peptidoglycan
no
what molecule does archaea have that is similar to peptidoglycan
pseudopeptidoglycan
other type of bacteria that has no cell wall
microbacteria
Gel-like layer outside cell wall that protects or allows attachment to surface
capsules and slime layers
distinct, gelatinous
capsule
diffuse, irregular
Slime layer
Allow bacteria to adhere to
surfaces
capsules and slime layers
allow bacteria to evade host immune system
capsules
unique type of dormant cell
Endospores
what kind of layers does archaea have
S-layers
Extremely resistant to heat, desiccation, chemicals, ultraviolet light, boiling water
Endospores
Endospores that survive can
germinate to become
vegetative cell
formation of endospores
▪ Sporulation
what is Sporulation triggered by
triggered by
carbon or nitrogen limitation
how long does it take for sporulation to complete
8 hours
maintains core in dehydrated state, protects from
heat
cotex
has small proteins that bind and protect DNA
Core
what is Germination triggered by
heat, chemical exposure
how long does germination take
1-2 hours
involved in motility
Flagella
types of Flagella
Peritrichous
Polar flagellum
how does flagella move
Spin like propellers to
three parts of flagella
- Filament - moves
- Hook
- Basal body
what is flagella is powered by in bacteria
proton pump
what is flagella is powered by in ATP
Archaea
Bacteria can sense what
chemicals
bacteria response to O2
Aerotaxis
bacteria response to earth’s magnetic field
Magnetotaxis
bacteria response to temperature
Thermotaxis
bacteria response to light
Phototaxis
are shorter
and thinner than flagella and
the function is differen
Pili (sing. pilus)
Common pili
fimbriae
allow the bacterial cells to attach to specific surfaces
fimbriae
help bacterial cells
move with a twitching or
gliding motility
pili
used to join bacteria for DNA transfe
Sex pilus
forms the nucleoid
▪Chromosome
gel-like region
nucleoid
are circular, supercoiled, dsDNA
Plasmids
antibiotic resistance can
spread how
sharing Plasmids with other bacteria
are involved in protein synthesis
Facilitate joining of amino acids
Ribosomes
how are Ribosomes’s size expressed
S (Svedberg)
Prokaryotic ribosomes are
70S
Eukaryotic ribosomes are
80S
can transport compounds
Buds off from organelle, fuses with membrane of another
Vesicles
Cytoplasmic membrane in eukaryotic cells
hospholipid bilayer embedded with proteins
Proteins in outer layer serve as
receptors
Bind specific molecule termed
ligand
Transport proteins in eukaryotic cells
- Carriers
- Channels
- Aquaporins
facilitated diffusion, active transport
Carriers
form small gated pores, allow ions to diffuse
Channels
water passage
Aquaporins
types of Endocytosis
Pinocytosis
Receptor-mediated endocytosis
Phagocytosis
most common in animal cells
Liquids and dissolved substances
Pinocytosis
Cell internalizes extracellular ligands binding to surface
Receptor-mediated endocytosis
used by protozoa, phagocytes to engulf
Phagocytosis
is the reverse of endocytosis
Exocytosis
- Secreted proteins carry a signal sequence that acts as a tag
- Vesicles transport tagged proteins
Secretion
does protein synthesis
ribosomes
allow movement
Actin filaments
are thickest component.
Make up mitotic spindles to separate chromosomes as cell divide.
Framework for organelle and vesicle movement
Microtubules
types of Microtubules
Cilia and flagella
provide mechanical support (physical stress)
Intermediate filaments
function in motility
Propel via whiplike motion or
thrash back and forth to pull
cell forward
Flagella
are shorter, move
synchronously
Can move cell forward or
move material past stationary
cell
Cilia
contains DNA
Nucleus
Nuclear pores allow
large molecules to pass
is region where ribosomal RNAs synthesized
Nucleolus
Nucleus surrounded by
two lipid bilayer membranes
generate ATP
Mitochondria
Mitochondria Bounded by
two lipid bilayers
Mitochondrial matrix contains
DNA and 70S ribosomes
evolved from bacterial cells
Endosymbiotic theory
are site of photosynthesis
Chloroplasts
Chloroplasts are found where
plants, algae
Harvest light energy to generate ATP
Chloroplasts
ancestors of mitochondria
and chloroplasts were bacteria
Endosymbiotic theory
