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Microbiology

Exam 1 - Chapter 4,5 and 7

QuestionAnswer
Prokaryotes Lack nucleus Lack organelles Are small, 1-10 µm in diameter Bacteria and Archaea
Eukaryotes Have nucleus Have internal membrane-bound organelles Are larger, 10–100 µm in diameter Algae, protozoa, fungi, plants & animals
Prokaryotes (External Features) Flagella Pili Fimbriae Glycocalyx (capsule) Cell walls Cytoplasmic membrane
Flagella -Are responsible for movement -Long structures that extend beyond cell surface -Can have one, many, or no flagella Monotrichous (A) Lophotrichous (B) Amphitrichous (C) Peritrichous (D)
Function of the Flagella -Rotation propels bacterium through environment -Rotation reversible; can be counterclockwise or clockwise rotation at up to 100,000 rpm! -Bacteria move in a series of runs and tumbles Runs: movement in a single direction Tumbles: abrupt change in dir
Movement of Bacteria -Bacteria move in response to stimuli (taxis): Phototaxis: light Chemotaxis: chemicals Negative taxis: unfavorable Positive taxis: favorable
Axial filament -Found in spirochetes -“Internal flagella” which is enclosed between cytoplasmic membrane and cell wall -Rotation of axial filament, causes corkscrew motion
Fimbriae -Sticky, bristle-like projections -Shorter than flagella -Used by bacteria to adhere to one another, to hosts & to surfaces in the environment -Serve important function in biofilms
Pili -Rigid, tubular projection -Longer than fimbriae but shorter than flagella -Only a few per cell -So far only found on Gram negative bacteria -Mediate the transfer of DNA from one cell to another
Glycocalyx Gelatinous, sticky substance surrounding outside of the cell, prevent bacteria from drying out
Two types of glycocalyces -Capsule Firmly attached to cell surface May prevent bacteria from being recognized by host -Slime layer Loosely attached to cell surface Sticky layer allows prokaryotes to attach to surfaces
Bacterial Cell Walls -Provide structure and shape -Protect cell from osmotic forces -Assist some cells in resisting antimicrobial drugs -Also, can be target of some antimicrobial drugs -Key in distinguishing Gram + and Gram - bacteria
Bacterial shapes and arrangements -Cocci: spherical -Bacillus: rod-shaped -Spirals: spiral-shaped -Pleomorphic: variations in cell shape
Cocci Single Two (diplococci) Four (tetrads) Chains (streptococci) Groups (staphylococci)
Bacilli Single Chains (streptobacilli)
Spirals Single
Bacterial Cell Wall Composition -Composed of peptidoglycan Alternating units of sugar molecules (NAM-NAG) -Two basic types of bacterial cell walls Gram-positive Gram-negative
Gram-positive Cell Walls Thick layer of peptidoglycan Contain molecules called teichoic & lipoteichoic acids Appear purple following Gram staining procedure
Gram-Negative Cell Walls Thin layer of peptidoglycan Additional bilayer membrane outside the peptidoglycan Contains lipopolysaccharide (LPS) Protect against harsh conditions Protection against some antimicrobials Dead cells releases lipid A which may cause fever, inflammatio
Bacterial Cytoplasmic Membranes-Structure -Referred to as phospholipid bilayer Composed of lipids and associated proteins -Fluid mosaic model
Bacterial Cytoplasmic Membranes-Function -Selectively permeable Naturally impermeable to most substances Proteins allow substances to cross membrane -Energy storage Cellular respiration Photosynthesis -Maintain concentration and electrical gradient Chemical gradient- maintain different c
Methods of transfer across the membrane Passive processes (move along natural concentration gradient, do not require energy)
Diffusion movement of molecules from areas of high concentration to low concentration
Facilitated diffusion diffusion, but requires the aid of proteins to cross the phospholipid bilayer
Osmosis diffusion of water across a selectively permeable membrane
Tonicity comparison of the concentrations of two solutions on either side of selectively permeable membrane
Hypertonic when uneven, the solution with the higher concentration
Hypotonic when uneven, the solution with the lower concentration
Isotonic same concentration on the both sides of a membrane
Prokaryotic Cytoplasmic Membranes Active processes -Active transport: movement of molecules against the concentration gradient, requires membrane proteins and energy -Group translocation: substance chemically modified during transport, modified substance is trapped inside cell, occurs
Internal Structures of Prokaryotes - Cytoplasm -Mostly water (70-80%) -Sugars, amino acids, salts -DNA, ribosomes, granules, actin
Internal Structures of Prokaryotes -Nucleoid -Region in cytoplasm containing DNA -Plasmids: small circular DNA not necessary for survival, genes for resistance or virulence
Internal Structures of Prokaryotes -Inclusions (granules) -Diagnostic for several pathogenic bacteria (Chlamydia) -May include reserve deposits of lipids, starch and other chemicals
Endospores -Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions -Extremely resistant to drying, heat, radiation, boiling, chemicals (bleach & alcohol) -Vegetative cell: bacteria capable of replicating, one vege
Internal Structures of Prokaryotes -No membranous Organelles- Ribosomes Sites of protein synthesis Smaller than eukaryotic ribosomes Target of antimicrobials
Cytoskeleton Plays a role in forming the cell’s basic shape
Photosynthetic bacteria Independent cells that can use energy from sunlight to convert inorganic molecules to necessary nutrients
Two major groups of Photosynthetic bacteria Cyanobacteria Green and purple sulfur bacteria
Cyanobacteria -(previously known as blue-green algae) -Membrane adaptations resemble thylakoids -Contain gas inclusions, allows them to float on surface of water -Provide oxygen to environment
Green and purple sulfur bacteria -Anaerobic, found deeper in water supplies -Use sulfur compounds in metabolism, do not give off oxygen
Nitrogen fixing bacteria -Most are soil-dwelling microbes with a synergistic relationship with plants -Capable of converting atmospheric nitrogen into compounds usable by plants Fixed nitrogen compounds then can be used by other organisms or recycled into soil by dying plants
Characteristics of Archaea vs. bacteria vs. eukaryotes -Most primitive of all life forms -Extremophiles Require extreme conditions to survive -Features similar to bacteria Prokaryotic, small Most are cocci, bacilli, or spiral forms Reproduce by binary fission, budding, or fragmentation -Features simila
Characteristics of Archaea -Features unique to Archaea Lack peptidoglycan Cell membrane lipids have branched hydrocarbon chains Different rRNA sequence -Not known to cause human disease -Thermophiles, halophiles, and methanogens
Thermophiles -Thrive at hotter temperatures -DNA, RNA, cytoplasmic membranes & proteins do not function properly below 45°C (113°F) -Hyperthermophiles – require temperatures over 80°C (176°F) -Hot acidic springs in deep ocean, volcanic habitats
Halophiles -Inhabit extremely salty habitats -Depend on greater than 9% NaCl to maintain cell walls some grow in 36% salt! normal cell salt conc. = 0.15% -Many contain red or orange pigments used to synthesize ATP -Dead Sea, salted fish, solar evaporation ponds
Methanogens -Largest group of Archaea -Convert carbon dioxide, hydrogen gas, and organic acids to methane gas -Convert organic wastes in pond, lake, ocean sediments & sewage treatment plants to methane -Some live in colons of animals One of primary sources of env
Eukaryotic Cells structure -Flagella -Structure Form within the cytoplasmic membrane, push membrane out Formed from a different type of protein May be single or multiple; generally found at one pole of cell -Function Movement, but can either push or pull organism through media Do not
Cilia -Shorter & more numerous than flagella -Coordinated beating Propels cell through their environment (protozoa) Facilitates feeding (protozoa) Move substances past the surface of the cell (respiratory and reproductive tracts)
Glycocalyx -Not as organized as prokaryotic capsules -Help anchor animal cells to each other -Strengthen cell surface -Provide protection against dehydration -Function in cell-to-cell recognition & communication
Eukaryotic Cells (cell wall) -Fungi, algae & plants have cell walls -Provides support, structure & protects against osmotic pressure -Composed of various polysaccharides that differ among organisms
Eukaryotic Cytoplasmic Membranes -All eukaryotic cells have a cytoplasmic membrane -Are a fluid mosaic of phospholipids and proteins Differ from prokaryotes Contain steroid lipids (cholesterol) Attach sugar (glyco) chains to membrane proteins and lipids to create more complex recep
Eukaryotic Cytoplasmic Membranes-Function -Controls movement into and out of cell -Use all passive & active processes, except group translocation -Maintain concentration and electrical gradients -Recognition molecules, enzymes, receptors, channels
Endocytosis -Endocytosis (substances brought into cell) Phagocytosis (solid substances) Pinocytosis (liquids)
Exocytosis Exocytosis (substances exported from cell)
Eukaryotic Cells (nucleus) -Often largest organelle in cell -Most cells have a single nucleus -Contains most of the cell’s DNA Chromatin = DNA & associated proteins -Contains one or more nucleoli Ribosomal RNA synthesis -Surrounded by nuclear envelope Two phospholipid bilaye
Eukaryotic Cells (endoplasmic reticulum) -Endoplasmic reticulum Netlike arrangement of flattened, hollow tubules continuous with nuclear envelope Functions as transport system
Endoplasmic reticulum -Two forms -Rough endoplasmic reticulum (RER) Adds functional groups to proteins Studded with ribosomes -Smooth endoplasmic reticulum (SER) Lipid synthesis Detoxification
Eukaryotic Cells (Golgi body) -Composed of flattened hollow sacs -Receives, processes, and packages large molecules (mainly proteins from the RER) for export from cell -Packages molecules in secretory vesicles that fuse with cytoplasmic membrane and release contents to outside
Eukaryotic Cells (vacuoles & vesicles) Vacuoles and Vesicles -General terms for membrane bound sacs -Vesicles are usually for transport -Vacuoles are usually for storage Animal cells have numerous small vacuoles Plant cells have one large central vacuole, mostly water Some microorganis
Lysosome -Found only in animal cells -Contains degradative enzymes Digest macromolecules into reusable units Breakdown of own damaged organelles to keep cell clean Digestion of bacteria in white blood cells
Peroxisome -Breakdown hydrogen peroxide, a harmful metabolic by-product -Detoxifies alcohol and other harmful products
Eukaryotic Cells (mitochondria) -Produce most of cell’s ATP (“powerhouse of cell”) -Have two membranes composed of phospholipid bilayer Inner one being very folded -Semi-autonomous Interior matrix contains 70S ribosomes (prokaryotic) Circular molecule of DNA Can divide without
Chloroplasts -Have two phospholipid bilayer membranes, inner one forming thylakoids -Light-harvesting structures found in photosynthetic eukaryotes -Similar to mitochondria Have own DNA Have 70S ribosomes
Ribosomes -Protein synthesis -Larger than prokaryotic ribosomes (80S vs. 70S) -Some are free in cytoplasm Synthesize proteins that stay in cell -Some attached to endoplasmic reticulum Synthesize proteins for export
Cytoskeleton -Extensive network of fibers & tubules Anchors & moves organelles Produces basic shape of cell Movement (amoeboid) Cell division
Created by: bonitasoul