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78 Cards in this Set
- Front
- Back
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Prokaryotic cell |
Smaller
Include bacteria archaea |
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What does the smaller size of prokaryotic cells enable it to do? |
High surface area to low volume allows for rapid uptake of nutrients and excretion of wastes. Also allows for rapid growth |
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Eukaryotic cells |
Have a true nucleus Larger, more complex Membrane bound compartments Eukarya |
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What are the two types of microscope? |
Light microscope Electron microscope |
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Light microscope key characteristics |
Can magnify 1000x
Important tool for microbiology
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Electron microscope characteristics |
Can magnify sample more than 100000x |
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Three key light microscopy concepts |
1. Magnification 2. Resolution 3. Contrast |
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Magnification |
Apparent increase in size |
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Two types of lenses in a compound microscope |
Objective and ocular |
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Resolution |
Resolving power Ability to distinguish two objects that are very close together |
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Contrast |
Determines how easily cells can be seen Transparent bacteria lack contrast and are difficult to see against a colorless backgrounds |
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What can be used to increase contrast? |
Stains. |
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What is one bad thing about stains |
Kill microbes |
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Fluorescense microscopes |
Cells are either naturally fluorescent or tagged with a fluorescent dye Increase contrast Absorb light at one wavelength and emit light at longer wavelength |
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What is the drawback to using an electron microscope? |
Lenses and specimen must be in a vacuum to prevent air molecules from interfering with electrons |
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Wet mount |
Uses a drop of liquid specimen |
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Smear |
Involves drying and fixing specimen before staining it to visualize it |
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Gram stain |
Most common type for bacteria |
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Two groups of gram stain |
Gram positive Gram negative |
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Capsule stains |
Stain the background of a cell instead of the actual cell Some microbes surrounded by gel-like layer |
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Endospore stain |
Resists gram stain, often appears as clear object |
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Flagella stain |
Since Flagella are too thin to be seen with a light microscope, a Flagella stain coats the Flagella to thicken it and therefore make it visible |
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Two most common prokaryotic cell shapes |
1. Coccus (spherical) 2. Rod (cylindrical) |
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How do most prokaryotic cells divide? |
Via binary fission |
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Every cell has a cytoplasmic membrane |
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Prokaryote characteristics |
Flagella Capsule Cell wall Cytoplasmic membrane |
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Capsule |
1. Usually made up of polysaccharides 2. Allows bacteria to adhere to surfaces 3. Allows bacteria to invade immune systems |
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Prokaryotic cell wall types |
Bacteria have two types of cell walls with differing structures: Gram positive Gram negative |
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Gram positive |
Thick layer of peptidoglucan |
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Gram negative |
Thin layer of peptidoglycan surrounded by an outer layer that contains LPS (liposaccharide) Periplasm |
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Characteristics of the cytoplasmic membrane |
1. Phospholipid bilayer embedded with proteins 2. Semipermeable membrane |
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Functions of proteins |
1. Selective gates 2. Sensors of environmental conditions |
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What does it mean that the lipid bilayer is semipermeable? |
Allows some molecules to pass while acting as a barrier to others |
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What things can pass freely through the membrane? |
1. Small hydrophobic molecules (CO2, O2, N2) 2. Water |
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Aquaporins |
Allow water to pass freely in some cells |
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Simple diffusion |
Movement from high concentration to low concentration Speed depends on concentration Gases, small molecules |
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Osmosis |
Diffusion of water across selectively permeable membranes due to unequal solute concentrations |
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What must molecules pass through to cross the membrane? |
Transport system (proteins that act as a selective gate) |
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Are proteins highly specific? |
Yes. They only transport their specific molecule type |
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Facilitated diffusion Rarely used in _______ not useful in _______ enviornments |
Form of passive transport
Movement down a gradient. No energy needed.
Rarely used in prokaryotes and not useful in low-nutrient environments |
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Active transport |
Requires energy Move against gradient |
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What are the two main mechanisms by which active transport can take place? |
1. ATP 2. Proton Motive Force |
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Cell wall |
Strong rigid structure that prevents cell lysis |
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How do gram positive and gram negative cells differ? |
Their cell walls are architecturally different |
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Peptidoglycan is unique to |
Bacteria |
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Prokaryotic cell wall structure |
Page 19 slide 29 |
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Why is LPS important medically? |
Signals body about infection Large amount in bloodstream can signal deadly response. |
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What is LPS called |
Endotoxin |
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What does the outer membrane of a gram negative prokaryotic cell wall do? |
Blocks passage of many molecules including antibodies Small molecules can pass via porins |
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Periplasmic space |
Space between inner and outer membrane in prokaryotic cells |
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Why do antibacterial substances target peptidoglycon? |
It is unique to bacteria and won't harm our important cells |
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How does penicillin work |
Interferes with peptidoglycan sysnthesis, breaking down the cell wall |
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What is lysozyme |
Breaks down bonds linking glycan chain Found in bodily fluids Destroys structural integrity in peptidoglycan molecule |
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Penicilin and lysozyme do not affect bacteria that do not have cell wall |
F |
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Mycoplasma species |
Have extremely variable shape |
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Archaea cell wall have variable shape and do not have peptidoglycan |
Js |
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Capsules can turn into biofilm |
Js |
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Polar flagellum |
Single flagellum at one end of the cell |
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Peritichous |
Flagella distributed over entire surface of cell |
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Three parts of a Flagella |
Filament Hook Basal body |
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Pili |
Shorter than flagella Twitching, gliding |
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Fimbrae |
Type of pili involved in attachment |
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Chromosome |
Single circular double stranded dna
Forms gel-like region: nucleoid Packed tightly |
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Plasmids |
Circular, supercoiled DNA Much smaller. Antibiotic resistance can be shared this way |
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Ribosomes |
Protein synthesis Join amino acids together Eukaryotic ribosomes are different than prokaryotes. Important because antibiotics can be made to affect prokaryotic ribosomes and not eukaryotic |
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Cytoskeleton |
Framework |
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Endospores |
Extremely resistant bacteria that are resistant to heating, chemicals, uv, boilin Can germinate to become typical cell |
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Sporulation |
Triggered by carbon, nitrogen limitation (nurruebf depletion) |
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Vesicles (eukaryotes) |
Can transport compounds between Buds off from one organelle, fuses with the membrane of another |
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Carrier proteins |
Facilitative diffusion active transport |
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Channels |
Form small gated pores, allow ions to sidduse |
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Endocytosis |
Take materials up via digestion |
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Receptor mediated endocytosis |
Cell internalizes extracellular ligands binding to surface |
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Phagocytosis |
Used by protozoa to engulf bacteria |
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Pinocytosis |
Cells take in liquid |
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Nucleus |
Transcription Nuclear pores DNA Two lipid bilayer membranes |
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Mitochondria |
Generate ATP Contains DNA 70s (pro) ribosomes |
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Endosymbiotic theory |
Theory that ancestors of mitochondria were bacteria |
