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ENH222 Midterm Review.docx

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Environmental Health
ENH 222
Marcia Maguire

AETIOLOGY STUDY SHEETS FOR MIDTERM EXAM LECTURE 2: MICROSCOPY AND LAB TECHNIQUES Describe a compound light microscope?  Series of lenses and uses visible light as source of illumination  Examine very small specimens (fine detail)  Ground lenses: forms focused image that is many times larger than the specimen itself  Magnification is achieved by:  Light rays from illuminator (light source) pass through a condenser (has lenses that direct the light rays through the specimen). Light rays pass through objective lenses (lenses closest to the specimen) Image of the specimen is magnified by ocular lenses What is total magnification?  Multiply the objective lens maginification (power) by the ocular lens magnification (power) What is resolution?  Ability of the lenses to distinguish fine detail and structure What are the uses for each type of microscope? Darkfield Microscope  Examine live microorganisms that are either invisible in the ordinary light microscope  Cannot be stained by standard methods  Distorted by staining therefore characteristics cannot be identified Phase Contrast microscope  Permits detailed examination of internal structures in living microorganisms Differential Interference Contrast Microscope (DIC)  Similar to phase contrast  Uses differences in refractive indexes  Image appears three dimensional Fluorescence Microscopy  Absorbs UV light and emits visible light Confocal Microscope  Laser scans each plane of specimen  Reconstruct three dimensional images  Evaluate cellular physiology by monitoring the distributions and concentrations of substances such as ATP and calcium ions. What is an electron microscope?  Uses electrons instead of light What does TEM stand for?  Transmission Electron Microscopy What is TEM used for?  Used for thin/foil specimens What does SEM stand for?  Scanning Electron Microscopy What is SEM used for?  Used for thick and bulky specimens What is simple stains?  Aqueous or alcohol solution of a single basic dye  Purpose is to highlight the entire microorganism so that cellular shapes and basic structures are visible  Mordant: chemical that is added to the solution to intensify the stain (increases affinity of a stain for a biological specimen + to coat structure in order to make it thicker and easier to see (flagellum) What is differential stains?  React differently with different kinds of bacteria and thus can be used to distinguish them  Differential stains most used for bacteria are the Gram Stain and the acid-fast stain What is Differential stains: Gram Stain?  Classifies bacteria as gram positive or gram negative  Gram positive bacteria: thick multilayer peptidoglycan walls + more sensitive to antibiotics such as penicillin  Gram negative bacteria: thin peptidoglycan cells walls + more resistant to antibiotics which cannot permeate LPS layer  Important in treatment surgeries What are special stains?  Negative stains are useful for capsules which are water soluble and may be dislodged during washing What are endospore stains (special stains)?  Bacillus cereus What are flagella stains? (Special stains)?  Spirillum volutans What are the four steps in preparing a gram stain? 1. Heat fixed smear is covered with a basic purple dye,usually crystal violet (primary stain) 2. Purple dye is washed off, and the smear is covered with iodine (mordant). When iodine is washed off both gram positive and gram negative bacteria appear dark violet or purple 3. Slide is washed with alcohol/alcohol acetone solution (decolorizing agent)which removes purple from the cells of some species but not others 4. Alcohol is rinsed off and the slide is then stained with safranin (Red dye). Smear is washed again, blotted dry and examined microscopically. Define gram positive  Bacteria that retain the dark violet or purple color after the alcohol has attempted to decolorize them Define gram negative  Bacteria that lose the dark purple or violet color after decolorization Define bacterial colonies  Population of cells arising from a single cell or spore or from a group of attatched cells What is the streak plate method?  Isolation method most commonly used to get pure cultures 1. Sterile incolutaing loop dipped into mixed culture and streaked over small sections of agar 2. Loop flamed 3. Next section of agar streaked by picking up a small amount of bacteria from the previous section 4. Repeat 5. Bacteria is diluted out and grown in isolated colonies LECTURE 3: PROKARYOTES AND EUKARYOTES Compare between prokaryotes and eukaryotes? Prokaryotes Eukaryotes One circular chromosome not in membrane Paired chromosome in nuclear membrane No histones histones No organelles organelles Peptidoglycan cell walls Cell walls or membranes Binary fission Mitotic spindle What are the basic shapes of bacteria?  Pairs and Chains: diplococcic, streptococci, single bacillus,diplobacilli, streptobacilli, coccobacillus, vibrio, spirillum, spirochete  Clusters: tetrad, sarcinae, staphylococci  Unusual shapes: star shaped stella , Square halo arcula Describe bacterial structures Capsule/Slime Layer  Outside cell wall  Composed of sticky polysaccharide or polypeptide  Neatly organized or unorganized and loose  Virulence factor (prevents phagocytosis +for attatchment) Flagella  Filaments with protein chains of flagellin  Attatched to protein hook  Basal body anchor to wall/membrane  Motility  Rotational propeller movement Axial Filaments  Found in sphirochetes  Endoflagella  Spiral bundles of fibrils  Anchored at one end of a cell  Rotation produces movement Fimbriae or Pili  used for attatchment rather than motility  gram negative  thinner than flagella Cell Walls  present in almost all prokaryotes  prevents osmotic lysis  peptidoglycans ( disachharides linked by polypeptides) Gram Positive Cell Walls  thick peptidoglycan  teichoic acids Gram Negative Cell Walls  thin peptidoglucan  no teichoic acids  outer membrane Plasma Membrane  thin structure enclosing cytoplasm  inside cell wall  phospholipid bilayer  Proteins (peripheral, integral, transmembrane) Cytoplasm  Inside plasma membrane  80% water  macromolecules Nuclear Area  chromosome/genome  single circular dsDNA Plasmid  extra chromosomal mobile genetic element Ribosomes  thousands of very small granular structures  site of protein synthesis  consists of protein and rRNA Inclusions  Metachromatic granules  Polysaccharide granules  Lipid inclusions  Sulfur granules  Carboxysomes  Gas vacuoles  Magnetosomes Endospores  Resting cells  Resistant to dessication, heat chemicals  Sporulation: endospore formation  Germination: Return to vegetative state Describe the process of sporulation 1. Spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm 2. Plasma membrane starts to surround DNA, cytoplasm and membrane isolated in step 1 3. Spore septum surrounds isolated portion, forming forespore 4. Peptidoglycan layer forms between membranes 5. Spore coat forms 6. Endospore is freed from cell Describe the following Eukaryotic Cell structures: Flagella and Cilia  Projections containing cytoplasm enclosed by plasma membrane  Anchored by basal body  Nine pairs of microtubules in ring  Two microtubules in center made of protein tubulin Cell Wall  Fungi – carbohydrate cell walls  Cellulose  Chitin  Glucan & mannan Plasma Membrane  Protozoa  Phospholipid bilayer  Sterols (Cholestrol)  Peripheral, integral transmembrane proteins  Carbohydrate pellicles Cytoplasm  Cytoplasm membrane: substance inside plasma and outside nucleaus  Cytosol: fluid portion of cytoplasm  Cytoskeleton: microfilaments, intermediate filaments, microtubules  Cytoplasmic streaming: movement of cytoplasm throughout cells Organelles  Nucleaus: contains chromosomes  ER: transport network  Golgi complex: membrane formation and secretion  Lysosomes: digestive enzymes  Vacuoles: brings food into cells and provides support  Mitochondrian: cellular respiration  Peroxisome: oxidation of fatty acids ; destroys H2O2  Ribosome: protein synthesis  Centrosome: protein fibers and centrioles  Centriole: mitotic spindle formation Nucleaus  Nucleaus: double membrane  Nuclear envelope: DNA + histones  Nucleolus: Threadlike protein mass  Chromatin: coils into chromosomes  Nuclear pores: allows communication with cytoplasm Endoplasmic Reticulum  Extensive network of flattened membraneous sacs or tubules  2 distinct forms (Rough ER & Smooth ER)  Rough ER: continuous with nuclear membrane, studded with ribosomes, synthesized proteins and phospholipids  Smooth ER: extends from rough ER, synthesizes fats and steroids Golgi Complex  Transport synthesized proteins from ER  Transfer vesicles modify and move proteins from ER  Secretory vesicles deliver proteins to plasma membrane for excretion Mitochondria  Appear throughtout cytoplasm  Double membrane  Large surface area for ATP production  Powerhouse of the cell  Contains 70S ribosome and DNA LECTU
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