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90 Cards in this Set
- Front
- Back
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Eukaryotes
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Light microscope allowed differentiation. have high degree of internal complexity, have a true nucleus enclosed by a membrane, membrane bound organelles, mitosis, and complex lipids
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Prokaryotes
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Archea and bacteria, no nucleus, no membrane bound organelles, have D-amino acids, have muramic acid
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Why are things that prokaryotes have important?
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We can take advantage of these uniquely prokaryotic structure to serve as targets for the action of antibiotics
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Shapes of bacteria
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1) Cocci- Sphere
2) Bacilli- Rod 3) Vibrios- Comma Shaped 4) Spirochetes- helical, flexible 5) Spirilla- helical, rigid 6) Staphylococci- grapelike group of cooci 7)Streptobacilli- long line of connected rod shaped cells |
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Why are gram-stain and shape so important?
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They are stable characteristics that help identify bacteria
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Structure of Capsule or Slime Layer
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Slime is a mucilaginous exterior covering with no distinct boundaries. Capsule is a mucilaginous exterior covering with optically distinct boundary
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Chemical Composition of Slime layer
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Variable.
Generally made of either protein or complex carbs. |
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Function of Capsule or Slime Layer
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No metabolic function. Probably prevents dessication. Often absent in laboratory cultured cells. WIthin the host the capsule can increase virulance by avoiding phagocytosis due to slipperiness. The capsule can also serve as a disguise by mimicing molecules on the host tissue. Finally, the capsule can promote adherence. Some capsular material is antigenic- results in Quellung Rxn.
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Gram Positive Cells
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Stain Purple. Cell surface is delineated by cell wall that is relatively thick and composed of a thick layer of covalently bonded peptidoglycan
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Gram- Negative Cells
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Stains pink. Outer layer is delineated by outer membrane followed by a thin cell wall with little peptidoglycan and little cross-linking and no peptide bridges.
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Medical Significance of the cell surface.
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1)It determine interaction with host defese mechanisms
2) Allows serological ID bc of antigens on surface 3)Provides many of the structures unique to bacteria that are targeted by abx's |
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Gram Stain History and Significance
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Devised by Christian Gram in late 1980's. Central to ID'ing most bacteria in most situations. Can determine prognosis and treatment. More difference between gram neg and pos cells than between us and yeast.
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Gram Stain Procedure
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-Sample dried and fixed on side
-flooded with crystal violet, both pos and neg take it up -Add gram's iodine that complexes with crystal violet to make large conjugate (mordant) -Washed with alcohol removes complexed stain from neg because of thinner cell wall but pos retains the complex and stays purple -Flooded with pink safranin stain which now only shows up in the neg cells |
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Cell Wall Biosynthesis and Antibiotics
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All antibiotics that will work on gram neg will also work on gram pos cells. The steps of the process the abx targets are common to both cell types. Often takes longer and larger doses to work on gram negative because of the permeability barrier of the gram negative outer membrane
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Cell Wall Synthesis
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Occurs in 3 sites
1) Synth of water soluble peptidoglycan subunits in the cytoplasm (no ribosomes or rna) 2)Transfer to and modification of cell wall components at the cell membrane. Gram pos cells get peptidoglycan crosslinks here 3)Polymer growth at the cell wall |
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Antibiotics acting on Cell wall Biosynthesis
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1) D-cyclosporine- inhibits racemase that converts l-alanin to d-alanine
2) Vancomycin- blocks subunit transfer from carrier lipid to growing peptide 3)Bacitracin- topical, blocks dephosphorylation to lipid carrier is not regenerted 4)Penicillin- inhibits transpeptidase reaction by preventing cross-peptide bridge formation |
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Lysozyme
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-Not an Antibiotic
-an enzyme -doesn't require cell to be actively growing -won't affect gram neg until outer wall is removed |
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Function of Cell Wall
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-Give shape and provide rigitidy under different osmotic conditions
-In the right osmotic condition some gram neg bacteria without cell wall (spheroplasts) can survive |
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Gram Negative Outer Membrane
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-External to peptidoglycan cell wall
- made of phospholipid, protein, and lipopolysaccharide (LPS) -Has porin proteins that make it sieve-like |
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Periplasmic Space
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-Only in gram negative cells
-between outer membrane and cytoplasmic membrane -variety of degradative enzymes, carrier enzymes |
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LPS
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- only in gram negative
-Located on the outer leaflet of the outer membrane -its carbohydrate groups face outward |
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Cytoplasmic Membrane Makeup
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-Structure is same for gram pos and gram neg
-Phospholipid bilayer with proteins involved in cell envelope biosyntehsis, transport, and the cytochrome |
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Function of Cytoplasmic Membrane
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-Selective permeability barrier
-Site of active transport -site of oxidative phosphorylation through electron transport sytem |
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Bacterial Cytoplasm
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-contains 50% of protein and most enzymes
-no membrane bound organelles |
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Visible Structures in Cytoplams
*only visible with electron microscope |
-Chromosomes- single closed circular, double stranded
- Plasmids- autonomously replicating covalently closed circular DNA elements that cary greatly in size and don't encode info vital for growth but things like abx resistance -Ribosomes- large RNA-protein complexes functioning in protein synthesis |
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Flagella
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-imparts motility
-polymarized subunits of flagellin added at the tip -very thin -antigenic so of diagnostic value -cells are peritrichous, monotrichous, or lophotrichous |
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Axial Filaments
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-Spirochetes
-like flagella in structure and fx in motility -originate at the poles and extend toward center of cell -enclosed in the outer membrane of the cell so not external to the cell |
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Pili
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-filamentous and made of protein
-pili are thinner and shorter than flagella - Assembled from the base -Don't confer motility -work in attachment -Function in Conjugation |
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Spores
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-Bacillus and Clostridium
-sporulation is not a reproductive stage but instead is a mechanism for survival in poor conditions -Resist killing by heat, drying, freezing, abx, and UV radiation -Autoclave can kill -Metabolically quiescent and dehydrated |
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Why do we like antibiotics directed against cell wall of bacteria?
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Unique to bacteria so side effects are reduced
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What kind of carbon compounds to bacteria of medical importance require?
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Reduced carbon sources- they breakdown and oxidize them for energy.
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All medically important bacteria are chemotrophs or phototrophs? Organotrophs or lithotrophs?
heterotrophs or autotrophs? |
-Chemotrophs- obtain energy from a chemical sources, not the sun
-They get their energy from organic sources to they are organotrophs. -Generate energy in tth form of ATP from electron transport chain and from substrate-level phosphorylation -They are heterotrophs- need growth factors like vitamins, amino acids etc. |
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Temperature Requirements
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-All are mesophilic (prefer 20-40 degrees C)
-temperature at which an organism grows best does not preclude it from growing at other temperatures (ex) listeria can grow at low temps) |
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Aerobes
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Some bact like e-coli, neisseria, and mycobacterium are aerobic
- can be obligate and have to have oxy - facultative and oxy is utilized but not required - microaerophillic and need a little oxy but too much is bad (lots like this bc in bloodstream ex) gonorrheae) |
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Anerobes
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Strepto and clostridium
-obligate anerobes- oxy is toxic (C. botulism) -Aerotolerant- oxy is tolerated but not used |
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Toxicity of Oxygen
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-All bacteria have enzymes capable of reacting with oxy can result in toxic hydrogen peroxide or superoxide
-aerobes and aerotolerant orgs have peroxidases and superoxide dismutase and catalase -All obligate anaerobes lack superoxide dismutase +/- catalase -Org lacking catalase may not be sesitive to oxy |
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Salt
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-ok with 1-2% salt and most dont do well with more
-Exception is staphylococcus aureus that does well in up to 8% |
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PH
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between 6-8 for most but as low as 1 and as high as 10
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CO2
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Some capnophilic bacteria do better with higher proportion of CO2 like that found in blood
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Anabolic
Catabolic Amphibolic |
Anabolic- Building ex) synth of tryptophan
Catabolic- Breaking down ex) embden meyerhof (glycolic) Amphibolic- link catabolism and anabolism ex)TCA cycle |
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Fermentation
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Nonoxidative breakdown of carbs to yield energy good for differentiating bacteria based on products and types of carbs that can be fermented
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Quiescent State
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Very few bacteria cause trouble while in the quiescent state so if DNA replication is blocked then growth stops event hough bacteria may not be dead
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Nalidixic Acid
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inhibits bacterial DNA synthesis by inhibiting DNA gyrase which gets rid of supercoiling of DNA generated during replication
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Transcription
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DNA into RNA
-involves RNA polymerase sensitive to abx |
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Rifampcin
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antibiotic that binds beta subunit of RNA polymerase and presents reading of DNA and transcription generally
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Protein Synthesis
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bacteria have 70s ribosomes (we have 80s) different enough to have antibiotics that target the bacterial ribosome but will cause side effects because we still have mitochondria with 70s ribosomes
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Chloramphenicol
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inhibits protein synthesis and peptidyl transferase- side effects
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Bacteria Cellular Division
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Divide by binary fission can be complete or incomplete and form two equally sized daughter.
Incomplete remain connected as in staphylococcus or streptobacilli |
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Population Growth
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Generation time (20m-20h) is time it takes for population to double which depends on nutrients and physical and chemical environment
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Measure Cell Growth
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- by turbidity
- by bacterial mass - plate count |
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Cell Death
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a cell that cannot grow is said to be dead- what about vaccines
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Mutation
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-affect the production of the gene product or the products ability to act
-change in nucleotide sequence |
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Substitution Mutation
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- change of one nucleotide for another
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Insertion or Deletion
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-One or more nucleotides are inserted or deleted
- can be a frameshift mutation if what is inserted or deleted is not a multiple of three |
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Mutagens
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Agents that increase mutation frequency
- disrupts or interferes with normal ydrogen bodning -UV light= Thymine Dimers - Base analogs - Relatively high mutation rate |
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Gene Transfer
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-Plasmids
-lysogenic bacteriphages - transformation - conjugation -transduction |
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Transformation
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transfer of naked DNA released by donor cell though lysis or artificially through chemical extraction
- then recombination can occur=> transformation |
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Conjugation
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Mating of two cell types
-e-coli -males have F factor (autonomously replicating plasmid) F+ - F factor can integrate into chromosome - F+ and F - mating- F+ donates copy of F factor - F and F'- F prime is f+ that integrated into chrom and excised improperly taking a small frag of dna with it -HFR and F- has whole chromosome and can integrate |
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R Factors
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plasmids that transmit resistance to one or more antibiotics ex) shigella
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Bacteriocinogenic
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plasmids that encode products that kill other bacteria ex) Colv
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Transduction
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transfer of genetic info by a phage can be either
- generalized- during packaging of virus picks up strand of bacterial DNA accidentally -specialized- involves particular phage that carries restricted region of DNA that is often adjacent to phage insertion site |
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Selective Media
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inhibit the growth of certain bacteria while allowing the growth of other bacteria
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Differential Media
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Distinguish one type of bacteria from another based on physiological differences which are indicated by color changes in the media or bacterial colony ex) MacConkey Agar
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Importance of immunology
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-can benefit host with immunity or harm with autoimmune disease
-can id infectious organisms through serology -skin testing for atopic dematitis |
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Innate Immunity
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-non specific
- first line of defense -rapid -no memory - skin, mucous, tears, saliva, cilia involved - humoral factors like complement, cell secreted factors like cytokines, and host leukocytes |
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Inflammation in Innate Immunity
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- bacteria enter
- swelling, redness, pain, and heat - infiltration of plasma and leukocytes |
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Phagocytes
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Neutrophils, dendritic cells, macrophages
- can phagocytose and kill bacteria - can produce chemical messages that attract more host antibacterial cells (cytokines) - Process and internalize bacteria and present to lyphocytes |
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Bactericidal Mechanism
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-antimicrobial peptides that damage mebranes
- opsonization- host molecules bind to and cause enhanced uptake of bacteria by phagocytes -phagocytosis |
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Adaptive Immunity
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-Second line of defense
-Specific to antigens -generated over time -characterized by immunological memory |
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Initiation of Adaptive Immunity
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Dendritic cells, macrophages, and B Lymphocytes are antigen present, present to T Cells that become activated, proliferate and generate clones that are specific to the antigen
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Types of Lymphocytes
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All originate in bone marrow
1)B lymphocytes differentiate in bone marrow and become antibody secreting plasma cells when activated by antigen 2) T Cells differentiate in the thymus to become either Helper T cells or cytotoxic T cells |
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Humoral Immunity
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mediated by antibodies
-recognize and bind to antigens on bacteria to help clear the bacteria by preventing it from binding to or entering host or opsonizing it or fixing complement |
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Cellular Immunity
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Deal with bacteria within host cells
mediated by T cell that provide help (cytokines) or kill host cells harboring intracellular bacteria |
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Antibody Structure
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Two identical heavy and two identical light chains with variable regions of amino acid sequence and has two binding sites (Bivalent) which allows cross-linking and agglutination
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IGM
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On B cell surfaces
complement fixation and agglutination primary immune response |
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IGG
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In tissue spaces
complement fixation and neutralization Secondary Immune Response |
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IGA
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In secretions
neutralization on mucosal surfaces |
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IGE
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Mast Cell sensitization
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IGD
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receptor for antigen on B cells
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Serology
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Diagnostic science that allows ID of specific antimicrobial antibodies in serum or microbes/microbial antigens through the se of antimicrobial antibodies
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Types of Lymphocytes
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All originate in bone marrow
1)B lymphocytes differentiate in bone marrow and become antibody secreting plasma cells when activated by antigen 2) T Cells differentiate in the thymus to become either Helper T cells or cytotoxic T cells |
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Humoral Immunity
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mediated by antibodies
-recognize and bind to antigens on bacteria to help clear the bacteria by preventing it from binding to or entering host or opsonizing it or fixing complement |
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Cellular Immunity
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Deal with bacteria within host cells
mediated by T cell that provide help (cytokines) or kill host cells harboring intracellular bacteria |
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Antibody Structure
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Two identical heavy and two identical light chains with variable regions of amino acid sequence and has two binding sites (Bivalent) which allows cross-linking and agglutination
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IGM
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On B cell surfaces
complement fixation and agglutination primary immune response |
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IGG
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In tissue spaces
complement fixation and neutralization Secondary Immune Response |
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IGA
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In secretions
neutralization on mucosal surfaces |
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IGE
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Mast Cell sensitization
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IGD
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receptor for antigen on B cells
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Serology
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Diagnostic science that allows ID of specific antimicrobial antibodies in serum or microbes/microbial antigens through the se of antimicrobial antibodies
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