microbiology ch4 Flashcards
light
affects our ability to visualize objects with the human eye
wavelength
*length of a light ray
*represented by Greek letter lamda
*equal distance between two adjacent crests or two adjacent troughs of a wave
resolution
*ability to see two items as separate and distinct units rather than one fuzzy overlapping image
*light must pass between objects to be seen as separate
*key: get light of short enough wavelength to fit between objects.
reflection
*light strikes an object and bounces back- reflection has occurred.
transmission
*the passage of light through an object
*most microorganisms will make use of transmitted light
absorption
*light rays neither bounce off nor pass through an object
*light rays are taken up by an object- absorption has occurred
iluminescence
*absorbed light rays are changed into longer wavelengths and reemitted
refraction
*bending of light as it passes from one medium to another of differing density
*gives rise to an angle of refraction or the degree of bend
index of refraction
*measures the speed at which light passes through a material
*substances that have different indices of refraction, light will bend as it passes from material to material
*can cause loss of light and blur an image
immersion oil
*oil joins the slide and lens together
*prevents refraction of the image
staining
*increases differences in indices of refraction
*makes it easier to observe detail
light microscope
*any microscope that uses visible light to make specimens observable
compound microscope
*a microscope with more than one lens
*gives distortion free image
monocular vs binocular lens
*monocular- single eyepiece
*binocular- two eyepieces
blue filter
*filters out long wavelengths of light, leaving shorter wavelengths and improves resolution
condenser
*converges the light beam so that it they pass through the specimen
iris diaphragm
controls amount of light that passes through the specimen to the objective lens
objective lens & total magnification
*magnifies the image before it passes through the body to ocular lens
* Scan- (4X) x (10X) = 40X total mag.
*Low power- (10X) x (10X) = 100X total mag.
*High-dry power- (40X) x (10X) = 400X total mag.
*Oil immersion- (100X) x (10X) = 1000X total mag.
mechanical stage
allows precise control of moving the slide
focus adjustment knobs
*coarse adjustment- changes distance between objective lens and specimen rapidly
*fine adjustment- changes the distance between the objective lens and specimen slowly
dark field microscopy
*microscope adapted for dark-field illumination have condenser that causes light to reflect off the specimen at an angle
*a light object is seen on a dark background
phase-contrast microscopy
*used to observe live specimen
*light is slowed down and diffracts the change in light speed, seen as different degrees of brightness
*short depth of field, can produce a nearly 3-D image.
fluorescent microscopy
*ultraviolet light used to excite molecules, so they release light of longer wavelengths
*produces a brilliant shade of orange, yellow, yellow green
digital microscopy
*they have auto-focus, auto-aperture, auto-light, motorized stage and magnification changers
*just plug in and power on
*magnification is limited on digital microscopes
electron microscopy
*allows small structures (less than 0.2 micrometers) to be visualized
*uses a beam of electrons and an electromagnet to focus the beam
*can resolve objects close to 20 nano meters (nm), magnifying at 50,000X total magnification
degree of contrast
the contrast between structures being observed and their background
wet mount
drop of medium containing the organism is placed on a microscope slide, can be used to view live organisms
smear
*organism is thinned out and smeared across a slide, then heat fixed
heat fixed
*kills the organism
*organism adheres to the slide
*alters the organism so that they readily accept the stain
staining
*stain dye is a molecule that can bind to a cellular structure and give it color
cationic stains
*positively charged and attracted to negatively charged organisms
*crystal violet, safranin, malachite green
*most bacteria are negatively charged
anionic stains
*negatively charged and attracted to positively charged organisms**
simple stain
uses a single dye to reveal basic shapes and arrangements of cells
differential stain
uses 2 or more dyes to distinguish between two kinds of organisms, as well as their shape and arrangement.
gram stain
*distinguishes between gram-positive, gram-negative, gram-nonreactive, and gram-variable
*reveals fundamental difference between the cell walls of bacteria
ziehl-neelsen acid-fast stain
*used to detect tuberculosis and leprosy causing organism Genus Mycobacterium
negative stain
*used when the capsule is resistant to stain
*stain the background will give the bacteria a clear look and the background a dark look.
flagellar staining
*painstaking process of staining the flagella surfaces with dye or metal such as silver
endospore staining
*used on bacteria that produce endospores
*malachite green stain is used then gently heated until they steam (5mins) then stained with safranin.
*cells will look red while endospores will look green
prokaryotic
*living cells without a nucleus
*single-celled organisms, all are bacteria
*DNA is in a nuclear region, lack organelles that are membrane enclosed
*smallest of all organisms (0.5 - 0.2) micro meters
eukaryotic
*living cells with a true nucleus
*multi-celled organisms
*plants, animals, fungi, protists
*DNA in a nuclear envelope, cells have organelles that are membrane-enclosed
*human rbc is about (7.5) micro meters in diameter
Cell domains
Archaea - prokaryotic
Bacteria - prokaryotic
Eukarya - eukaryotic
biological classification
domain
kingdom
phylum
class
order
family
Genus
species
Prokaryotes: shapes
*spherical - coccus
*rodlike - bacillus
*spiral - vibrio (common), spirillum (wavey), spirochete (corkscrewed)
*spindle, *irregular lobed, *square bacteria, *triangular
Prokaryotes: arrangement
cocci - one plane pair (diplo), chain (strepto)
two planes (tetrads) 4 cells in a cube
three planes (sarcinae) 8 cells cube arranged
grape-like clusters (staphylo)
bacilli - one plane but connect end to end or side by side
spiral - not generally grouped together
Prokaryotes: cell wall
*semi-rigid, outside the cell membrane
*maintains the characteristic shape of the cell
*prevents cell from bursting when fluid flows into cell
Prokaryotes: component of cell wall
*peptidoglycan- 40layers gram +, few layers in gram -
*outer membrane- found in gram -, lipopolysaccharide- is a toxic substance, can cause fever, dilate blood vessels, and drop blood pressure
*periplasmic space- gap between cell membrane and cell wall, active area of metabolism
gram-positive bacteria
*cell wall is thick, made of peptidoglycan, holds stain well
*older cells don’t keep stain well
gram-negative bacteria
*cell wall thinner, more complex
*10-20% of cell wall is peptidoglycan, the rest is lipid, polysaccharides, proteins
*take up safranin dye due to lipid layer
Prokaryotes: cell membrane
*boundary between cell and its environment
*same general structure of phospholipids and proteins
*phosopholipid bilayer- phosphate head, fatty acid tail
Prokaryotes: internal structure cell
*ribosomes - protein synthesis
*nuclear region or nucleoid, mainly DNA, some RNA
*vacuoles
*cytoplasm - semifluid substance
*endospores - helps cell survive, resistant to heat, drying, acids, bases, disinfectants, & radiation
Prokaryotes: external structure cells
*flagella - provides movement, long-thin helical appendage
*pili - tiny projections, attach bacteria to other surfaces
*conjugation pili- connect 2 cells, may transfer dna
*short pili- attachment pili adhere to surfaces
*capsule - protective structure outside the cell wall, only certain bacteria
chemotaxis & phototaxis
*chemotaxis - movement towards or away from a substance in their environment, nonrandom
*phototaxis - movement towards or away from light in their environment, nonrandom
Eukaryotic: cell structure
*larger more complex, contain more highly differentiated structures
*plasma membrane - less functional than prokaryotes, no respiratory enzymes to capture ATP (mitochondria does that)
Eukaryotic: internal cell structure
*cytoplasm - smaller portion of cell, more organelles
*cell nucleus - nucleic envelope, DNA & RNA
*mitochondria - powerhouse, oxidative reactions, ATP capture
*ribosomes - assembled in nucleoid of the nucleus, protein synthesis
*endoplasmic reticulum - smooth ER - lipid synthesis
rough ER - protein synthesis
*golgi apparatus - receive substances from ER, stores
*lysosomes - made by golgi app. contain digestive enzymes, fuse with vacuoles to ingest substances and destroy them
*peroxisomes - convert hydrogen peroxide to water
*vacuoles - membrane-enclosed structure, stores materials, engulf food particles (endocytosis)
Eukaryotic: external structure
*flagella - for movement, whip like, only sperm cells in humans
*cilia - short numerous, same composition as flagella, aid in movement, mucociliary escalator
movement of substances across membrane
*passive transport- cell expends no energy to move substances, moves from are of high concentration to area of low concertation
*active transport - cell expends energy ATP, enabling substances to move against concentration gradient
*simple diffusion - passive transport
*facilitated diffusion - passive transport aided by pores or carrier molecules
endocytosis and exocytosis
*cells move substances by forming membrane (vesicle) around substance.
*endocytosis - vesicle invagination and surrounds substances from outside the cell
*exocytosis - cells release secretions outside of the cell by vesicles
metabolism
sum of all chemical processes carried out by living organisms
anabolism
*reactions that require energy to synthesize complex molecules to simpler ones
*needed for growth, reproduction, and repair of cellular structures
catabolism
*reaction that releases energy by breaking complex molecules into simpler ones, can then reuse and build with
*provide organisms with energy for its life processes; movement, transport, synthesis of complex molecules
glycolysis
*oxidation of glucose to pyruvic acid
*does not require oxygen, small amount of ATP captured
steps of glycolysis
- phosphorylation - 2 phosphates are used, 2ATP > 2ADP
- fructose molecule split into 2, 3-carbon molecules (glyceraldehyde 3-phosphate)
- NAD oxidized & reduced when enzyme brings in a phosphate (2 hydrogen atoms, along with their electrons to be transferred to NAD) electrons transfer to coenzyme NAD
- energy is captured in the form of ATP, pyruvic acid is formed, net 2 ATP per glucose molecule
fermentation
*converts pyruvic acid to ethyl alcohol, lactic acid, or other organic compounds
*does not require oxygen, small amount of ATP captured
steps of fermentation
*process of pyruvic acid metabolized in the absence of oxygen
*result of needing to recycle the limited amount of NAD by passing the electrons of reduced NAD off to other molecules.
aerobic respiration
*oxidation of pyruvic acid to carbon dioxide and water
*requires oxygen, large amount of ATP captured
steps of aerobic respiration - Krebs cycle: prelude
*pyruvic acid converted to acetyl-CoA by removal of one molecule of CO2, transfer to electrons to NAD, and addition of coenzyme A (CoA)
pyruvic acid combines with coenzyme A to form Acetyl CoA
metabolic pathway
series of chemical reactions in which the product of one reaction serves as the substrate of the next
enzymes
*act as catalysts to speed up reactions (as much as 1million X) its normal rate
*lower activation energy so reactions can occur easier
*activation/binding site - enzyme form loose association with a substrate
*specific to only one type of reaction/ one substrate
action energy
the energy needed to start a reaction
coenzymes and cofactors
*coenzyme - nonprotein molecule bound to/loosely associated with an enzyme
*cofactor - inorganic ion, improve the fit of an enzyme with its substrate, allow reaction to proceed
Krebs Cycle
*occur in mitochondria in eukaryotes
*sequence of reactions in which acetyl groups are oxidized to carbon dioxide
*hydrogen atoms removed, and their electrons are transferred to coenzymes
*each reaction in krebs cycle is controlled by specific enzymes and molecules are passed from one enzyme to the next as they go thru the cycle.
*as one acetyl group is metabolized, oxaloacetic acid combines with another to form citric acid, & the cycle repeats
*result: net gain of 2 ATP
electron transport and oxidation phosphorylation
*occurs in the mitochondria
*transfer of electrons from substrate (NADH & FADH) to O2
*NADH gives up electrons, electrons move from one protein to the next, as they move, energy is released, pumps H+ ions from mitochondria to intermembrane space
*oxygen captures electrons
*H+ ions that were removed, H+ ions diffuse through ATP synthase, H+ ions release energy to ATP synthase, and use energy to convert ADP to ATP (oxidative phosphorylation)
*result: ETS has a net of 34 ATP captured
