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Micro ch. 3 microscopy and cell structure


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What is resolution?
shortest distance between two objects where they can be observed as two objects
What things on the microscope improve resolution?
condenser=focuses light
iris diaphragm=controls amount of light
What are two types of electron microscope?
transmission= electrons transmitted thru specimen (1D)
scanning= electrons scan surface (2D)
What is a differential stain?
distinguishes b/w 2 features, uses 2 or more dyes
What is a simple stain?
1 stain, allows to see cell shape, size, and arrangement
What are the stages of a gram stain (differential stain)
1- primary= crystal violet (all purple)
2- mordant= iodine (all purple)
3- decolorizer=alchohol (most important)(gram - clear, gram + purple)
4- counterstain=safranin (g.-red, g.+ purple)
What are types of special stains?
endospore stains
flagella stains
acid stain
What is an endospore?
resistant form of bacteria created under stress, forms only in Clostridium and Bacillus (found in soil and animal intestine)
How does flourescent microscopy work?
attached flourescent dye to antibody of bacteria
ex. mycobacterium, and streptococcus
What are the different shapes of bacteria?
coccus (round); rod bacillus; coccobacillus, vibrio, spirilium, spirochete
How are bacterial cells grouped?
-chains either diplococcus or multiple cocci
What is an example of diplococcus grouping?
neisseria gonorrhea
What is an example of chains of cocci?
What is an example of clusters?
staphyloccocus or toxic shock syndrome
How does flagella move?
composed of flagallin, propels anti-clockwise (runs) and clockwise (tumbles), must have receptors to sense chemical attractant or detractant
What are Pili?
numerous appendanges that attach to different surfaces based on specific protein, found only in g.- bacteria ex. e-coli, cholera
What is the role of Pili?
twitching and gliding, conjugation, and cell recognition
What is conjugation?
sex pilus attaches between cells allowing passage of DNA, promotes better adaptation to environment
What is a plasmid?
small piece of DNA that carries a specific gene for a specific function. improves resistance against antibiotics
What are the types of glycocalyx?
capsule and slime layer, both are sticky and allow bacteria to remain in colony and stick to a surface
What is a capsule?
rigid, gelatinous layer connected to cell wall ex. dental plaque caused by streptococcus mutans
What is a slime layer?
diffuse, irregular loose aggregates of polysaccharides ex. biofilms
What is the role of glycocalyx?
-prevents nutrient and water loss
-protection, prevents against phagocytosis
What is the role of the cell wall?
rigid structure determines shape and prevents bursting in dilute soln
How is the cell wall removed?
1-pcn prevents formation of peptidoglycan
2-lysozymes-breakdown peptidoglycan layer
What is an example of a bacteria that lacks a cell wall?
mycoplasma pneumoniae= causes walking pneumonia, not affected by pcn or lysozomes, has sterols that give rigidity
What is the cell structure of gram positive bacteria?
-thick layer of peptidoglycan connected by interbridge to cytoplasmic membrane. (pcn attacks here)
-contains techoic acid= antigenic that stimulates immune systen
What is the cell structure of gram negative bacteria?
-outermost layer=lipopolysaccaride, contains endotoxin that leads to allergic reaction and septic shock
-thin inner layer of peptidoglycan
What is the cytoplasmic membrane (cell membrane)
thin fluid phopholipid bilayer embedded with proteins, hydrophillic head, hydrophobic tails
What is the role of the cell membrane?
-selective barrier=controls what enters and leaves
-generate of energy in prokaryotes that respire or photosynthesize
What is the role of the membrane protein?
-active transport of nutrients that cannot pass through bilayer
-transport waste and secretions out of cell
-enzymes break down polymers too large to enter
-receptors sense and respond to environment
What is simple diffusion?
diffusion of small molocules of 02,C02, and H2O through bilayer, does not require energy
What is active transport?
special transport systems bring in amino acids, organic acids and salts into cell. requires ATP
What is the chromosome?
single circular double stranded DNA molecule that is foled and twisted in supercoiled in region of cytoplasm. every gene is essential for survial
What are ribosomes?
catalyses protein synthesis, composed of protein and rRNA, composed of 2 subunits

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