Midterm 1 Review Flashcards
Robert Hook proposed what?
The cell theory
Louis pasteur proposed what?
spontaneous generation,
microbes are present in the air, shoed the importance of the aseptic technique.
Robert koch found what?
bacteria caused disease
What are the 4 important parts of koch’s postulates?
- Organism should be constantly present
- organism must be cultivated in a pure culture away from the animal body
- the culture when in animals should cause disease symptoms
- organism should be re isolated from these experimental animals and cultured again in lab (same as original organism)
What is the order when using microbial nomenclature?
genus followed by specific epthat
Who discovered the 3 domain system based on cellular organization?
Carl woose(1978)
What does the 3 domain system consist of and classify each?
- Bacteria - cell walls contain peptidoglycan
- archaea - cell walls lack peptidoglycan
- eukarya - protists, fungi, plants and animals
What are prokaryotes?
unicellular organisms, bacteria and archaea, genetic material NOT in nucleus
What are fungi, protozoa and algae considered?
eukaryotes
how do viruses differ from other microorganisms?
need electron microscope to visualize, nucleic acid core, need cells of other organisms to reproduce
how do prokaryotes typically divide?
binary fission
what is the average size of a bacterial cell?
0.2-2.0um * 2-8 um
How does light microscopy work?
uses visible light to observe specimens
what is compound light microscopy?
total magnification achieved through a series of lenses
what is resolution?
ability of lenses to distinguish between two points a specified distance apart
What is the difference between bright field and dark field microscopy?
Bright field: requires good contrast, staining changes refractive index
Dark field: image is visualized only by reflected light, specimen appears light against dark background, useful for specimens that are difficult to stain
what is phase contrast microscopy?
allows detailed examination of internal structures, based on wave nature of light rays, brings together diffracted and direct light rays
What is differential interference contrast (DIC)
uses two beams of light split by prisms, higher resolution, three dimensional
What is fluorescence microscopy?
specimens can fluoresce naturally or by fluorochromes, specimens absorb short wavelengths and emit longer wavelengths
What is electron microscopy?
required to visualize smaller structures than 0.2 um
what are stains usually made up of?
salts containing chromophore
what are some basic dyes and how do they work?
chromophore (positive ion), crystal violet, mehtelyne blue, safranin. the positive ion is attracted to the negative surface on the bacterial cell surface
What are some acidic dyes and how do they work?
chromophore (negative ion), acid fuchsin, nigrosin, eosin.
what can alter the staining effectiveness ?
pH
what is the fundamental staining procedure?
- fixation (kills cells, solidifies)
- staining (visibility)
- application of mordant (change permeability, hasten reaction)
- decolorization (tests degree of attachment of dye to cell)
- counter stain (difference between original stain and decolorized cells)
when is a simple stain used?
to visualize basic structure and shape (aqueous or alcohol solution of a single basic dye)
what is an acid fast stain?
binds only to bacteria with a waxy cell wall, decolorizes non acid fast bacteria
what is negative staining?
used for capsule staining (appear as halos)
what counterstain does endospore staining use?
safranin
what does a flagella stain consist of?
uses a mordant and carbolfuchsin
how much water does the average microbial cell contain?
70 %
what are three pros of water in microbiology?
ideal solvent, nutrient transport across cell, good temp. buffer
what is the ideal pH for microorganisms?
6.5-8.5
what type of bacteria are most likely to be present in more acidic environments?
fungi
what is an acidophile?
bacterium which grows below 4.0
what is an alkaliphile?
organism growing best at a high pH (cyanobacteria)
why are carbohydrates important in bacteria cells?
cell wall structure
why are lipids important?
structure and function, ideal permeability barriers, support and nutrient passage
what do fatty acids consist of?
polar head(phosphate group, glycerol) non polar tail (fatty acid)
what do phospholipid membranes do?
provide a barrier
what elements do proteins consist of?
C,H,O,N
what are proteins good for?
enzymes as catalysts
what are proteins made up of?
amino acids
how can protein denaturation occur?
unfavourable temperature, pH or salt concentrations
what are nucleic acids made up of?
DNA and RNA (purine and pyridimine)
what is the main difference between DNA and RNA?
DNA (double stranded helix)
RNA (single stranded)
what are the three main types of RNA?
messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA)
What does ATP consist of?
adenosine unit and three phosphate groups
what are the 6 characteristics of a living system?
- metabolism
- reproduction and growth
- differentiation
- communication
- movement
- evolution
what are the two main ways to classify organisms?
energy source and carbon source
what is the difference between a phototroph and chemotroph?
phototroph-light is primary source of energy
chemotroph- inorganic or organic compounds for energy
what is the difference between and autotroph and a heterotroph?
autotroph- carbon dioxide source (lithotroph)
heterotroph- organic carbon source (organotroph)
what does anoxygenic photosynthesis consist of?
green and pruple bacteria, contains bacteriophylls, uses sulfur compounds to reduce carbon dioxide
what do photoheterotrophs consist of?
use light for energy and organic C source, green non sulfur bacteria, purple non sulfur bacteria
what uses organic compounds as energy and co2 as primary carbon source?
chemoautotrphs
what are 3 inorganic energy sources?
hydrogen, sulfide, sulfur, ammonia, nitrite,iron
what are chemoheterotrophs?
the energy and carbon sources are the same organic compound
what are also considered saprophytes and parasites?
chemoheterotrophs
why do smaller prokaryotes have a bigger advantage?
reflected by larger surface relative the the cell volume compared to large cells
what is the formula for structure
(S/V)/(3/r)
- smaller the r larger the S/V ratio
how does a higher surface area and volume affect the growth of a cell?
the higher the S/V the more rapid the growth
how does the radius compare to nutrient transfer?
the smaller the radius the more efficient the transfer of nutrients
why is a function of the cytoplasmic membrane?
seperation from environment, contains proteins and phospholipids, barrier for entry and exit, reactions occur, site of energy conservation
what is an archaeal membrane?
lipids contain ether linkages rather than ester linkages, fatty acid side chains are replaced by isoprene, lipid monolayer rather than bi layer
what is the difference between passive and active transport?
passsive- no energy requires
active- requires enery
what is the function of a permeability layer?
prevents leakage and functions as gateway for transport of nutrients into cell
what is a protein anchor?
it is the site of proteins involved in transport, biogenerics and chemotaxis
what is the difference between simple diffusion and facilitated diffusion?
simple diffusion- net movement from high concentration to low concentration until equilibrium
facilitated diffusion- substance combines with transporter and protein facilitates movement across the membrane
what your osmosis?
net movement of water from low solute concentraion to high across semi permeable membrane
what is osmotic pressure?
pressure required to stop osmotic flow
what is the difference between isotonic, hypotonic and hypertonic solution?
isotonic- concentration inside and out are equal
hypotonic- outside is lower than in
hypertonic-inside is lower than out
what is required for active transport to occur?
low nutrient environments, require energy in form of ATP, high energy compound, dependent on transporter proetins
what does it mean when transport proteins use a high degree of specificity?
may only react with a single molecule or specific class of molecules
what are the three classes of membrane transporting systems?
- involve only membrane spanning(simple)
- involve a periplasmic-binding and membrane spanning (group translocation)
- involve series of proteins that cooperate to mediate transport event (ABC system)
what are the three types of simple transporters?
- uniporter- proteins that transport a molecule in undirectional fashion
- symporter- transports with another substance (H)
- antiporter- transports in one direction and another substance in the opposite direction
where does group translocation occur?
only in prokaryotes
In what type of transport is the substance chemically altered and impermeable to the membrane?
group translocation
what type of transport in best in low concentrations?
group translocation
what is the abc system?
periplasmic binding protein dependent transport, proteins within periplasm of gram negative bacteria mediate the transport event, energy comes from atp
what is the primary function of the cell wall?
prevent cell rupture
what is the cell wall composed of?
murein(peptidoglycan), alternating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
Describe gram + cell walls
several layers of peptidoglycan, contain teichoic acid
Describe gram - cell walls?
thin peptidoglycan layer not rigid, include outer membrane , peptidoglycan in the outer membrane is situated in the periplasm
what gram cell (+ or -) contains high concentrations of degradative enzymes and transport proteins?
-
what gram cell has an outer membrane composed of lipposacharides and assists in evading phagocytosis?
-
how do outer membrane porins assist in gram negative cells?
serve as channels to allow passage of essential molecules
what are atypical cell walls?
no wall or very small
what is the smallest known bacteria that can reproduce outside host cells?
mycoplasm
what is cytoplasmic space made up of?
cytoplasm, 80% water, nucleoid, ribosomes, inclusions
what is a nucleoid?
bacterial chromosome consisting of a single, continuous strand of DNA cirrcular, attatched to plasma membrane
what makes up 20% of cell volume and can be occupied by genetic material during active growth?
nucleotides
what are small cirrcular double stranded dna molecules and replicate independent of chromosomal dna?
Plasmids
what is the site for protein synthesis?
ribosomes
what are ribosomes called in prokaryotes?
70s ribosomes
what are inclusions?
reserve deposits found in prokaryotic cellsinclude metachromatic granules, polysaccharide granules, lipid inclusions, sulfur granules
what are endospores?
specialized resting cell produced by certain Gram-positive bacteria, environmentally tolerant to heat
describe endospore formation
- endospore formed within the vegetative cell (also called sporogenesis)
- usually initiated by a lack of available nutrients or environmental stress
- spore septum forms initially - isolating replicated chromosome and a portion of the cytoplasm
- septum thickens into a membrane and the forespore is formed
- layers of peptidoglycan are laid down after which protein layers form creating a spore coat
- once mature, vegetative cell ruptures and dies, releasing the endospore
what is germination?
eturn to the vegetative state as a result of physical or chemical damage to the endospore coat
what are 3 characteristics of endospores?
- not a means of reproduction
- resistant to adverse conditions
- composition and activity different from vegetative cell
- a lot of Ca
- low water content
what is glycocalyx?
gelatinous polymer composed of polysaccharide, polypeptide
What is EPS?
extracellular polysaccharide – so called when glycocalyx is comprised of sugar molecules
what are two microorganisms protected by gycocalyx?
Klebsiella: polysaccharide capsule allows adherence to respiratory tissue and protects from phagocytosis
Streptococcus mutans: glycocalyx allows attachment to surface of teeth
what are the 4 possible arrangements of flagella?
- monotrichous: single, polar
- amphitrichous: tuft at each end
- lophotrichous: two or more at one pole
- peritrichous: distributed over entire cell
how does flagellar structure differ in Gram - and Gram + ?
Gram-negative bacteria contain two pairs of rings in the basal body; outer pair anchored to the cell wall and inner pair anchored to the plasma membrane
Gram-positive bacteria typically contain only the inner pair of rings attached to the plasma membrane
how is movement achieved with flagella?
rotation of the flagellum from the basal body either clockwise or counterclockwise
