Med Micro Module #2

  1. Describe 4 major processes of living cells
    • Growth – increase size
    • Reproduction – increase in number
    • Responsiveness – react to environment
    • Metabolism – control chemical reactions
  2. Similarities of both  Prokaryotic and Eukaryotic cells
    • Both have:
    • DNA
    • Ribosomes
    • Cytoplasm
    • Plasma membrane
  3. Diferences between Prokaryotic and eukaryotic cells
    • Prokaryotic:
    • Oldest cell type
    • Small & simple
    • Lack nucleus
    • Lack organelles
    • Single-celled Single circular chromosome  

    • Eukaryotic:
    • Larger and more complex
    • Contain nucleus
    • Contain organelles
    • Single-celled or multicellular
  4. Describe Glycocalyces
    • Gelatinous -sticky substance surrounding the outside of the cell.
    • Composed of polysaccharides (sugar), polypepties (protein) or both.
    • 2 types : Capsule & Slime Layer
  5. Describe Capsule Glycocalyx
    • hard shell, firm
    • Composed of organized repeating units of organic chemicals
    • Firmly attached to cell surface
    • May prevent bacteria from being recognized by host
  6. Describe Slime Layer Glycocalyx
    • Not a firm structure
    • Loosely attached to cell surface
    • Water soluble
    • Sticky layer allows prokaryotes to attach to surfaces
  7. 3 main parts of Bacterial Flagella
    • Basal body – anchor flagella to cell
    • Hook – connect basal body to filament
    • Filament – does the movement

    The filament extend beyond cell surface

    Flagella not present on all bacteria
  8. Function of Bacterial flagella
    Responsible for movement

    • Rotation propels bacterium through environment (like a propeller), movement is different in Eukaryotes.
    • Rotation reversible: can be counterclockwise or clockwise Bacteria move in response to stimuli (taxis)
    • Runs – counterclockwise
    • Tumbles - clockwise
  9. List and describe 4 Bacterial flagellar arrangements
    • Peritrichous – flagella all over the cell
    • Single polar – flagella at one end
    • Tuft of polar – several at one end
    • Axial Filament – aka – spirochete, is incorporated inside the cell, rather than outside the cell body. Corkscrews as it        moves forward.
  10. Describe common shapes of bacterial cells
    • Cocci – spherical/round
    • Bacilli – rod shaped
  11. Describe common arrangements of bacterial cells
    • Arrangements
    • Individual - one cell
    • Chains – streptococci
    • Clusters – staphylococci
    • Cuboidal packets - carcinae
  12. Compare and contrast cell walls of Gram-positive and Gram-negative bacteria in terms of structure and Gram staining
    Both: Peptidogycan, but different thicknesses

    Gram Positive (+) Bacteria Cell Wall

    • Simple structure
    • Relatively thick layer of peptidoglycan with lipoteichoic acid
    • Lipoteichoic acid – anchors peptidoglycan to cell membrane
    • Appears purple following Gram staining procedure

    Gram Negative (-) Bacteria

    • Cell Wall Have only a thin layer of pepidoglycan
    • Outer bilayer membrane outside the peptidoglycan contains phospholipids, proteins and lipopolysaccaride (LPS)
    • LPS – stimulates the human immune system to freak out.
    • If infected with a gram (-) bacteria you feel more sick & feel more symptoms. 
    • Appear pink following Gram staining procedure.
  13. Compare and contrast cell walls of acid-fast bacteria with normal Gram-positive
    Acid-Fast Bacteria have waxy lipids in their cell walls. The waxy covering helps the cells survive drying out and makes them difficult to stain with regular water-based dyes.

    Gram (+) Cell Wall have a thick layer of peptidoglycan.
  14. Describe structure and clinical implications of Gram-negative cell walls
    • The Gram (-) outer membrane can prevent the movement of antibiotics to the underlying peptidoglycan, making the drug ineffectual against many gram (-) pathogens.
    • In a dead gram (-) bacteria, the cell outer cell membrane disintegrates, it releases endotoxins (Lipid A) that can accumulate in the blood, causing shock, fever and blood clotting.
  15. Draw phospholipid bilayer and explain its significance in reference to cytoplasmic membrane
    A cytoplasmic membrane is typically composed of phospholipid molecules arranged in a double-layer configuration called a phospholipid bilayer.
  16. Explain fluid mosaic model of membrane structure
    Things can move all directions in the cytoplasmic space.
  17. Describe function of a cytoplasmic membrane in relation to permeability
    The selectively permeable cytoplasmic membrane prevents the passage of some substances while allowing other substances to pass through protein pores or channels, sometimes requiring carrier molecules.
  18. Compare and contrast the passive and active processes by which materials cross membrane
    Passive processes – move chemicals across the cytoplasmic membrane require not energy expenditure by the cell.

    • Can occur 3 ways: diffusion, facilitated diffusion & osmosis
    • Diffusion – molecular size & concentration gradients determine the rate of this process
    • Facilitated diffusion – depends on the electrochemical gradient and carriers within the membrane that allow certain substances to pass through the membrane.
    • Osmosis – refers specifically to the diffusion of water molecules across a selectively permeable membrane.

    Active processes – transport require cell energy from ATP.

    • Substances move against its electrochemical gradient via carrier proteins.
    • Carriers may move two substances in the same direction at one (symports) or move substances in opposite directions (antiports)
    • Group translocation occurs in prokaryotes, during which the substance being transported is chemically altered in transit.
  19. Osmosis
    the diffusion of water across a semi-permeable membrane
  20. Isotonic
    when solutions on either side of a selectively permeable membrane have the same concentration of solutes
  21. Hypertonic
    the solution with the higher concentration of solutes
  22. Hypotonic
    solution with a lower concentration of solutes
  23. Describe bacterial cytoplasm and its basic contents
    • Cytosol - liquid portion of cytoplasm
    • Inclusions - storage of chemicals or macromolecules Inclusions not found in all bacteria. 
    • Nonmembranous organelles - such as nucleoid and ribosomes
  24. Describe formation & function of endospores
    • Unique structure produced by some bacteria that are a defensive strategy against unfavorable conditions.
    • Endospores allow the bacteria a way to defend against unfavorable conditions.
  25. Describe structure and function of ribosomes
    Sturcture - composed of protein and ribosomal RNA, in a  nonmembranous organelles, found in both prokaryotes and eukaryotes

    Function - make proteins
  26. Describe structure and function of the cytoskeleton
    Structure - a network of protein fibers that maintain the basic shape of prokaryotes.

    • Function
    • Main function is to maintain shape.  In some cells, he helps in cell division and contracts to help move through its environment.
  27. Describe the composition & function of Eukaryotic glycocalyces
    • Is a sticky substance anchored to its cytoplasmic membrane via covalent bonds to membrane proteins and lipids.
    • The function of eukaryotic glycocalyces help anchor animal cells to each other, strengthen the cell surface, protect from dehydration, and functioning in cell to cell recognition and communication.
    • Glycocalyces are absent in eukaryotes with at have cell walls, such as plants and fungi.
  28. Compare and contrast prokaryotic and eukaryotic cell walls
    Prokaryotic Cell Wall 

    • Provide shape & support against osmotic pressure. 
    • Bacteria cell walls are composed of peptidoglycan. 
    • Archaea cell walls are composed of protein or polysaccharides, but not peptidoglycan.

    Eukaryotic Cell Wall – wall less eukaryotic cells have glycocalyces, which are not found with eukaryotic cells that have walls.
  29. Compare and contrast prokaryotic and eukaryotic cytoplasmic membranes
    • Prokaryotic
    • Bacteria - composed of phospholipid molecules arranged in a double-layer configuration called a phospholipid bilayer.
    • Archaea – are phospholipids,  built with ether linkages rather than ester linkages (bacteria)

    • Eukaryotic
    • contain sterols such as cholesterol, wich act to strengthen and solidify the membranes when temperatures rise and provide fluidity when temperatures fall.
  30. Contrast exocytosis and endocytosis
    • Exocytosis – an active export of substances out of a cell, process requiring the expenditure of energy from ATP. Like waste/secretions.
    • Endocytosis – substances are surrounded by pseudopods and brought into the cell. Called phagocytosis involves solid substances/ pinocytosis involves liquids.  Like bacteria, viruses, aged and dead cells, liquid nutrients in extracellular solutions.
  31. Compare and contrast the cytoplasm of prokaryotes and eukaryotes
    • Both Have:
    • nonmembranous organelles
    • cytosol (liquid inside the cell)

    • Prokaryote Cytoplasm
    • Inclusions in cytosol are deposits of various substances (aka storage).

    • Eukaryote Cytoplasm
    • Has membranous organelles: nucleus, endoplasmic reticulum, golgi body, lysosomes, peroxisomes, vacuoles & vesicles, mitochondria, chlopoplasts.
  32. Identify Nonmembraneous Organelles in Prokaryotes & Eukaryotes
    Prok - Ribosomes, Cytoskeleton (some)

    Euk  - Ribosomes, Cytoskeleton, Centromeres (only animals)
  33. Identify Membraneous Organelles in Prokaryotes & Eukaryotes
    Prok - none

    Euk - nucleus, endoplasmic reticulum, golgi body(some), lysosomes (some), peroxisomes (some), vacuoles (some) & vesicles, mitochondria (most), chlopoplasts (plants & algae)
  34. Compare and contrast structure and function of prokaryotic and eukaryotic flagella
    • Prokaryotic Flagella
    • Long, extend beyond the surface of a cell and its glycocalyx & propel the cell through its environment.
    • Allow cells to move toward favorable conditions, and away from unfavorable stimuli.
    • Not all bacteria have flagella.
    • Movement - Rotate (counterclockwise/clockwise) about the basal body. 

    • Eukaryotic Flagella
    • Have no hook and the basal bodies & shafts are arrangement of microtubules.
    • Located - within the cytoplasmic membrane. Being internal, it pushes the cytoplasmic membrane out around them. 
    • Single or multiple flagella and are generally found at one end of the cell. 
    • Movement - undulate in a wave that moves down the flagellum. 
    • Not all Eukaryotes have flagella.
  35. Describe the function of cilia
    • Internal hairlike structure that allow the cell to move.
    • They extend the surface of the cell and are shorter and more numerous than flagella.
    • Found is some Eukaryotes.
    • No prokaryotic cells have cilia.
  36. Compare and contrast eukaryotic cilia and flagella
    • Like flagella, cilia are composed of microtubules, have the same internal structure.
    • Differ, flagella are longer and less numerous than cilia.
  37. Compare and contrast ribosomes in prokaryotes and eukaryotes
    Similar in that they function in protein synthesis.

    • Differ in that:
    • Eukaryotes – large (80S) in cytosol and on ER, smaller (70S) in mitochondria and chloroplast.
    • Prokaryotes – small (70S)
  38. Cytosol
    Semitransparent fluid composed of water containing dissolved and suspended proteins, ions, carbohydrates, lipids and wastes.
  39. Ribosomes
    • Function - Protein synthesis
    • Structure - found in the cytosol and many are attached to the membranes of the endoplasmic reticulum.
  40. Cytoskeleton
    Structure - internal scaffolding of fibers that tubles. Composed on tubulin microtubules (like in flagella and cilia)

    Function - Acts to anchor organelles and functions in cytoplasmic streaming and in movement of organelles within the cytosol.  In some cells, it allows the cells to contract, move the cytoplasmic membrane during endocytosis and amoeboid action and produce the basic shapes of the cells.
  41. Centrioles
    Found in animal cells and some fungal cells; each cell contains 2, which lie at right angles to each other near the nucleus, in a region of the cytoplasm called the centrosome.
  42. Nucleus
    largest organelle in cell, contains most of the cell’s DNA, surrounded by a nuclear envelope
  43. Endoreticulum
    Structure - Netlike arrangement of flattened, hallow tubules, continuous with nuclear envelope.

    Functions as transport system,

    • 2 types:
    • Smooth endoplasmic reticulum (SER) – makes lipids
    • Rough endoplasmic reticulum (RER) – protein folding occurs
  44. Golgi Body
    • Structure - flattened hallow sacs surrounded by phospholipid bilayer
    • Function - group things together and send them to specific places in the cell.
    • Post Office - for the cell: Receives, processes, and packages large molecules for export from cell.
    • Packages molecules in secretory vesicles
    • Not in all Euk. Cells.
  45. Vesicle & Vacuole
    General term for membranous sacs that function to store and transfer chemicals within eukaryotic cells. Include Lysosomes & peroxisomes.
  46. Vacuoles
    Found in plant and algal cells that store starch, lipids and other substances in the center of the cell.
  47. Lysosomes
    Function - Store & transfer chemicals within animal cell, contain catabolic enzymes. The enzymes is used during self-destruction of old, damaged and diseased cells and to digest nutrients that have been phagocytized.
  48. Peroxisomes
    Store & transfer chemicals within a cell, contain enzymes that degrade poisonous waste
  49. Mitochondria
    produce most of cell’s ATP; have two membranes composed of phospholipid bilayer; interio matrix contains ribosomes and molecules of DNA
  50. Chloroplast
    light-harvesting structure found in photosynthetic eukaryotes; have two phospholipid bilayer membranes and DNA (similar to mitochondria)
  51. Identify 2 primary metric units used to measure diameter of microbes
    • Micrometer(µm) = 10-6
    • Nanometer (nm) = 10-9
  52. List metric units in order of length from meter to nanometer
    • Meter = 1m = 39.37 inches (about 1 yard)
    • Decimeter (dm) = 10-1
    • Centimeter (cm) = 10-2
    • Millimeter(mm) = 10-3
    • Micrometer(µm) = 10-6
    • Nanometer(nm) = 10-9
  53. Define microscopy
    The use of light or electrons to magnify objects.
  54. Discuss relationship between contrast and staining in microscopy
    • Contrast refers to differences in intensity between two objects or between an object and its background.
    • One way to increase contrast between MO and their background is to stain them.
  55. Contrast simple and compound microscopes
    Simple Microscope – contains a single magnifying lens, similar to magnifying glass

    Compound Microscope – uses a series of lenses for magnification. Light passes through specimen into objective lens Oil immersion lens increases resolution Have one or two ocular lenses Most have condenser lens (direct light through specimen)
  56. Bright-field
    • when you want to look at stuff (basically 90% of the time).
    • If this does not show enough can use other types.
  57. Dark-field
    • Will increase the contrast and enable observation of more details than are visible in BFM.
    • Useful for examining small or colorless cells.
  58. Phase
    Greater resolution of internal structures.

    Used to examine living MO that would be damaged or altered by attaching them to slides or staining them.
  59. Nomarski
    • Produces a 3D effect.
    • This technique produces unnatural colors, which enhance contrast.
  60. Fluorescent
    • Direct UV light source at specimen.
    • UV light increases resolution and contrast is improved because fluorescing structures are visible against a black background.
    • Some cells are naturally fluorescent; others must be stained.
    • Used in immune-fluorescence to identify pathogens and to make visible a variety of proteins.
  61. Confocal
    • Also use fluorescent dyes or fluorescent antibodies, but these microscopes use UV lasers to illuminate the chemicals in only a simple plane
    • Each image from a confocal is an “optical slice” through the specimen, if it had been thinly cut.
    • A computer is used to construct a 3D representation, which an be rotated and viewed from any direction.
    • Useful in examining biofilm
  62. Compare transmission and scanning electron microscopy
    • Transmission EM
    • images are in cross sections & are in black & white. 2D image;
    • used to observe internal ultra-structural detail of cells and observation of viruses and small bacteria.
    • May be color enhanced.   

    • Scanning EM
    • are cool looking 3D images; 3D view of the surface of microbes and cellular structures;
    • used to observe the surface details of structures.
    • Specimens prepared for EM are dried cuz water vapor from a wet specimen would stop the electron beam.
  63. Describe probe microscopes
    Uses microscopic probes that move over the surface of a specimen.

    • 2 types:
    • Scanning Tunneling – used to observe the surface of objects; provide extremely fine detail, high magnification and great resolution
    • Atomic Force – used to observe living specimens at the molecular and atomic level.
  64. Explain purposes of a smear, heat fixation, and chemical fixation to prep a sample for microscopy
    • Smear – spread culture in thin film over silice
    • Heat Fixation – pass through a flame, smear side up, to fix specimen to slide.
    • Chemical Fixation – use a chemical (methyl alcohol) to fix specimen to slide.
  65. Describe the uses of acidic and basic dyes
    • Acidic Dyes – they stain alkaline structures and work best in acidic environments. Used in negative staining. 
    • Basic Dyes – they stain acidic structures. These are used more commonly, cuz most cell are negatively charged.
  66. Simple Staining Process
    • Composed on a single basic dye (crystal violet, safranin or methylene blue), simple because they involve no more than soaking the smear in the dye for 30-60 seconds, rinsed (water), blot dry, observe the smear.
    • Used to determine size, shape, and arrangement of cells.
  67. Gram Staining Process
    • Differentiate between two large groups of MO: Gram (+) & Gram (-) cells
    • Is the first step a med. Lab tech performs to identify bacterial pathogens.

    • Steps
    • Primary Stain – slide is flooded with crystal violet for 1 min., then rinsed with water. All cells are stained purple.
    • Mordant – Slide is flooded with iodine for 1 min., then rinsed with water. Iodine binds to dye to make less soluble, all cells remain purple.
    • Decolorization – Slide is flooded with ethanol-acetone solution for 10-30 sec., then rinsed with water. The cell walls of gram (-) are broken down, stain and mordant wash away. Gram (+) stain remain purple, Gram (-) stain are now colorless.
    • Counterstain – slide is flooded with safranin for 1 min., then rinsed with water and blotted dry. Gram (+) are purlple, Gram (-) are pink.
  68. Acid-Fast Staining
    • Used to stain mycobateria because waxy cell walls.
    • Mycobaceria = Pink (carbolfuchsin), other cells = Blue (methylene blue)
  69. Endospore Stainning
    • Used to stain endospores;
    • Endospores = Green (malachite green), cell = Red (safranin)
  70. Histological Stainning
    2 popular stains for histological specimens

    • Gomori Methenamine Silver (GMS) Used to find fungi (carbohydrates) in tissues
    • Hematoxylin and Eosine (H&E) Used to highlight differences in cell features (acidic vs. basic), bacteria
  71. Negative (Capsule) Stainning
    • Used to NOT stain bacterial capsules which have negatively charged cell surfaces.
    • Bacteria & Background = Purple (eosin), Capsule = Clear (repel dye)
  72. Flagellar Stainning
    Used to stain flagella Flagella = Dark
  73. Discuss purpose of classification and identification of organisms
    • The goal of modern taxonomy is to reflect a phylogenetic hierarchy; that is, that the way in which organisms are grouped should reflect their evolution from common ancestors.
    • Linnaeus based his taxonomic scheme primarily on organisms’ structural similarities.
  74. Discuss difficulties in defining species of microbes
    • Ribosomal nucleotide sequences have given microbiologist a new way to define prokaryotic species.
    • Some scientist propose that porkaryotes whose rRNA sequence differs more that of other prokaryotes by more than 3% be classified as a distinct species.
  75. Define the taxonomic hierarchy from general to specific
    K, P, C, O, F, G, S
  76. Name the procedures and tests used to identify and classify microbes
    • Physical Characteristics
    • Biochemical Test
    • Serological Test
    • Phage Typing
    • Analysis of Nucleic Acids
  77. How do you ID & Classify microbes by Physical characteristics?
    • Cell morphology (shape – coccus, bacillus, spiral)
    • Colony morphology (shape or color)
    • Identifying features (endospores, flagella, capsule)
  78. How do you ID & Classify microbes by Biochemical Test
    Biochemical tests

    Carbohydrate utilization

    • Add cells to tubes with carbohydrate and pH indicator and inverted tube to trap gas produced
    • Metabolize carb – make acid (yellow) Not metabolize carb = no acid produced (red)

    Production of Hydrogen Sulfide (H2S)

    • Add cells to tubes with media + Iron.
    • If produce H2S = ppt formed (black) NO H2S produced = no change (orange)  

    All in one: Rapid Identification System
  79. How do you ID & Classify microbes by Serological test?
    • Is an Agglutination Test
    • Add cells to media with antibodies to specific MO
    • Clumping = Positive result (antibodies are present)
  80. How do you ID & Classify microbes by Phage Typing?
    • Use viruses (bacteriophages) that infect bacteria.
    • Bacterial cells are grown in lawn on plate.
    • Drops of specific phage virus added to plate surface.
    • If virus can infect bacterial cells, Clearing = Plaques
  81. How do you ID & Classify microbes by Analysis of Nucleic Acids?
    Evaluating nucleic acids, DNA or RNA sequencing
Card Set
Med Micro Module #2
Chp 3 & 4