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Microscopy and Cell Structure. Chapter 3. Microscope Techniques Microscopes. Microscopes Most important tool for studying microorganisms Use viable light to observe objects Magnify images approximately 1,000x Electron microscope, introduced in 1931, can magnify images in excess of 100,000x

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microscope techniques microscopes
Microscope TechniquesMicroscopes
  • Microscopes
    • Most important tool for studying microorganisms
    • Use viable light to observe objects
    • Magnify images approximately 1,000x
      • Electron microscope, introduced in 1931, can magnify images in excess of 100,000x
      • Scanning probe microscope, introduced in 1981, can view individual atoms
principles of light microscopy
Principles of Light Microscopy
  • Light Microscopy
    • Light passes through specimen, then through series of magnifying lenses
    • Most common and easiest to use is the bright-field microscope
    • Important factors in light microscopy include
      • Magnification
      • Resolution
      • Contrast
principles of light microscopy1
Principles of Light Microscopy
  • Magnification
    • Microscope has two magnifying lenses
      • Called compound microscope
      • Lens include
        • Ocular lens and objective lens
          • Most bright field scopes have four magnifications of objective lenses, 4x, 10x, 40x and 100x
    • Lenses combine to enlarge objects
      • Magnification is equal to the factor of the ocular x the objective
        • 10x X 100x = 1,000x
principles of light microscopy2
Principles of Light Microscopy
  • Magnification
    • Bright field scopes have condenser lens
      • Has no affect on magnification
      • Used to focus illumination on specimen
principles of light microscopy3
Principles of Light Microscopy
  • Resolution
    • Usefulness of microscope depends on its ability to resolve two objects that are very close together
      • Resolving power is defined as the minimum distance existing between two objects where those objects still appear as separate objects
      • Resolving power determines how much detail can be seen
principles of light microscopy4
Principles of Light Microscopy
  • Resolution
    • Resolution depends on the quality of lenses and wavelength of illuminating light
      • How much light is released from the lens
    • Maximum resolving power of most brightfield microscopes is 0.2 μm (1x10-6)
      • This is sufficient to see most bacterial structures
      • Too low to see viruses
principles of light microscopy5
Principles of Light Microscopy
  • Resolution
    • Resolution is enhanced with lenses of higher magnification (100x) by the use of immersion oil
      • Oil reduces light refraction
        • Light bends as it moves from glass to air
        • Oil bridges the gap between the specimen slide and lens and reduces refraction
          • Immersion oil has nearly same refractive index as glass
principles of light microscopy6
Principles of Light Microscopy
  • Contrast
    • Reflects the number of visible shades in a specimen
    • Higher contrast achieved for microscopy through specimen staining
principles of light microscopy7
Principles of Light Microscopy
  • Examples of light microscopes that increase contrast
    • Phase-Contrast Microscope
    • Interference Microscope
    • Dark-Field Microscope
    • Fluorescence Microscope
    • Confocal Scanning Laser Microscope
principles of light microscopy8
Principles of Light Microscopy
  • Phase-Contrast
    • Amplifies differences between refractive indexes of cells and surrounding medium
    • Uses set of rings and diaphragms to achieve resolution
principles of light microscopy9
Principles of Light Microscopy
  • Interference Scope
    • This microscope causes specimen to appear three dimensional
      • Depends on differences in refractive index
    • Most frequently used interference scope is Nomarski differential interference contrast
principles of light microscopy10
Principles of Light Microscopy
  • Dark-Field Microscope
    • Reverse image
      • Specimen appears bright on a dark background
        • Like a photographic negative
    • Achieves image through a modified condenser
principles of light microscopy11
Principles of Light Microscopy
  • Fluorescence Microscope
    • Used to observe organisms that are naturally fluorescent or are flagged with fluorescent dye
      • Fluorescent molecule absorbs ultraviolet light and emits visible light
      • Image fluoresces on dark background
principles of light microscopy12
Principles of Light Microscopy
  • Confocal Scanning Laser Microscope
    • Used to construct three dimensional image of thicker structures
    • Provides detailed sectional views of internal structures of an intact organism
      • Laser sends beam through sections of organism
      • Computer constructs 3-D image from sections
principles of light microscopy13
Principles of Light Microscopy
  • Electron Microscope
    • Uses electromagnetic lenses, electrons and fluorescent screen to produce image
    • Resolution increased 1,000 fold over brightfield microscope
      • To about 0.3 nm (1x10-9)
    • Magnification increased to 100,000x
    • Two types of electron microscopes
      • Transmission
      • Scanning
principles of light microscopy14
Principles of Light Microscopy
  • Transmission Electron Microscope (TEM)
    • Used to observe fine detail
    • Directs beam of electrons at specimen
      • Electrons pass through or scatter at surface
        • Shows dark and light areas
          • Darker areas more dense
    • Specimen preparation through
      • Thin sectioning
      • Freeze fracturing or freeze etching
principles of light microscopy15
Principles of Light Microscopy
  • Scanning Electron Microscope (SEM)
    • Used to observe surface detail
    • Beam of electrons scan surface of specimen
      • Specimen coated with metal
        • Usually gold
    • Electrons are released and reflected into viewing chamber
    • Some atomic microscopes capable of seeing single atoms
microscope techniques dyes and staining
Microscope TechniquesDyes and Staining
  • Dyes and Staining
    • Cells are frequently stained to observe organisms
    • Satins are made of organic salts
      • Dyes carry (+) or (-) charge on the molecule
        • Molecule binds to certain cell structures
      • Dyes divided into basic or acidic based on charge
        • Basic dyes carry positive charge and bond to cell structures that carry negative charge
          • Commonly stain the cell
        • Acidic dyes carry positive charge and are repelled by cell structures that carry negative charge
          • Commonly stain the background
microscope techniques dyes and staining1
Microscope TechniquesDyes and Staining
  • Basic dyes (+) more commonly used than acidic dyes (-)
  • Common basic (+) dyes include
    • Methylene blue
    • Crystal violet
    • Safrinin
    • Malachite green
microscope techniques dyes and staining2
Microscope TechniquesDyes and Staining
  • Staining Procedures
    • Simple stain uses one basic stain to stain the cell
      • Allows for increased contrast between cell and background
      • All cells stained the same color
        • No differentiation between cell types
microscope techniques dyes and staining3
Microscope TechniquesDyes and Staining
  • Differential Stains
    • Used to distinguish one bacterial group from another
    • Uses a series of reagents
    • Two most common differential stains
      • Gram stain
      • Acid-fast stain
microscope techniques dyes and staining4
Microscope TechniquesDyes and Staining
  • Gram Stain
    • Most widely used procedure for staining bacteria
    • Developed over century ago
      • Dr. Hans Christian Gram
    • Bacteria separated into two major groups
      • Gram positive
        • Stained purple
      • Gram negative
        • Stained red or pink
dyes and staining
Dyes and Staining
  • The Gram Stain
microscope techniques dyes and staining5
Microscope TechniquesDyes and Staining
  • Acid-fast Stain
    • Used to stain organisms that resist conventional staining
    • Used to stain members of genus Mycobacterium
      • High lipid concentration in cell wall prevents uptake of dye
      • Uses heat to facilitate staining
        • Once stained difficult to decolorize
microscope techniques dyes and staining6
Microscope TechniquesDyes and Staining
  • Acid-fast Stain
    • Can be used for presumptive identification in diagnosis of clinical specimens
    • Requires multiple steps
      • Primary dye
        • Carbol fuchsin
          • Colors acid-fast bacteria red
      • Decolorizer
        • Generally acid alcohol
          • Removes stains from non acid-fast bacteria
      • Counter stain
        • Methylene blue
          • Colors non acid-fast bacteria blue
microscope techniques dyes and staining7
Microscope TechniquesDyes and Staining
  • Special Stains
    • Capsule stain
      • Example of negative stain
      • Allows capsule to stand out around organism
    • Endospore stain
      • Staining enhances endospore
      • Uses heat to facilitate staining
    • Flagella stain
      • Staining increases diameter of flagella
        • Makes more visible
morphology of prokaryotic cells
Morphology of Prokaryotic Cells
  • Prokaryotes exhibit a variety of shapes
    • Most common
      • Coccus
        • Spherical
      • Bacillus
        • Rod or cylinder shaped
        • Cell shape not to be confused with Bacillus genus
morphology of prokaryotic cells1
Morphology of Prokaryotic Cells
  • Prokaryotes exhibit a variety of shapes
    • Other shapes
      • Coccobacillus
        • Short round rod
      • Vibrio
        • Curved rod
      • Spirillum
        • Spiral shaped
      • Spirochete
        • Helical shape
      • Pleomorphic
        • Bacteria able to vary shape
morphology of prokaryotic cells2
Morphology of Prokaryotic Cells
  • Prokaryotic cells may form groupings after cell division
    • Cells adhere together after cell division for characteristic arrangements
      • Arrangement depends on plan of division
        • Especially in the cocci
morphology of prokaryotic cells3
Morphology of Prokaryotic Cells
  • Division along a single plane may result in pairs or chains of cells
    • Pairs = diplococci
      • Example: Neisseria gonorrhoeae
    • Chains = streptococci
      • Example: species of Streptococcus
morphology of prokaryotic cells4
Morphology of Prokaryotic Cells
  • Division along two or three perpendicular planes form cubical packets
    • Example: Sarcina genus
  • Division along several random planes form clusters
    • Example: species of Staphylococcus
morphology of prokaryotic cells5
Morphology of Prokaryotic Cells
  • Some bacteria live in groups with other bacterial cells
    • They form multicellular associations
      • Example: myxobacteria
        • These organisms form a swarm of cells
          • Allows for the release of enzymes which degrade organic material
          • In the absence of water cells for fruiting bodies
      • Other organisms for biofilms
        • Formation allows for changes in cellular activity
cytoplasmic membrane
Cytoplasmic Membrane
  • Cytoplasmic membrane
    • Delicate thin fluid structure
    • Surrounds cytoplasm of cell
    • Defines boundary
    • Serves as a semi permeable barrier
      • Barrier between cell and external environment
cytoplasmic membrane1
Cytoplasmic Membrane
  • Structure is a lipid bilayer with embedded proteins
    • Bilayer consists of two opposing leaflets
      • Leaflets composed of phospholipids
        • Each contains a hydrophilic phosphate head and hydrophobic fatty acid tail
cytoplasmic membrane2
Cytoplasmic Membrane
  • Membrane is embedded with numerous protein
    • More that 200 different proteins
    • Proteins function as receptors and transport gates
    • Provides mechanism to sense surroundings
    • Proteins are not stationary
      • Constantly changing position
        • Called fluid mosaic model
cytoplasmic membrane3
Cytoplasmic Membrane
  • Cytoplasmic membrane is selectively permeable
    • Determines which molecules pass into or out of cell
      • Few molecules pass through freely
  • Molecules pass through membrane via simple diffusion or transport mechanisms that may require carrier proteins and energy
cytoplasmic membrane4
Cytoplasmic Membrane
  • Simple diffusion
    • Process by which molecules move freely across the cytoplasmic membrane
      • Water, certain gases and small hydrophobic molecules pass through via simple diffusion
cytoplasmic membrane5
Cytoplasmic Membrane
  • Simple diffusion
    • Osmosis
      • The ability of water to flow freely across the cytoplasmic membrane
      • Water flows to equalize solute concentrations inside and outside the cell
        • Inflow of water exerts osmotic pressure on membrane
          • Membrane rupture is prevented by rigid cell wall of bacteria
cytoplasmic membrane6
Cytoplasmic Membrane
  • Membrane also the site of energy production
  • Energy produced through series of embedded proteins
    • Electron transport chain
    • Proteins are used in the formation of proton motive force
    • Energy produced in proton motive force is used to drive other transport mechanisms
cytoplasmic membrane7
Cytoplasmic Membrane
  • Directed movement across the membrane
    • Movement of many molecules directed by transport systems
      • Transport systems employ highly selective proteins
        • Transport proteins (a.k.a permeases or carriers)
          • These proteins span membrane
          • Single carrier transports specific type molecule
        • Most transport proteins are produced in response to need
      • Transport systems include
        • Facilitated diffusion
        • Active transport
        • Group translocation
cytoplasmic membrane8
Cytoplasmic Membrane
  • Facilitated diffusion
    • Moves compounds across membrane exploiting a concentration gradient
      • Flow from area of greater concentration to area of lesser concentration
        • Molecules are transported until equilibrium is reached
      • System can only eliminate concentration gradient it cannot create one
      • No energy is required for facilitated diffusion
      • Example: movement of glycerol into the cell
cytoplasmic membrane9
Cytoplasmic Membrane
  • Active transport
    • Moves compounds against a concentration gradient
    • Requires an expenditure of energy
    • Two primary mechanisms
      • Proton motive force
      • ATP Binding Cassette system
cytoplasmic membrane10
Cytoplasmic Membrane
  • Proton motive force
    • Transporters allow protons into cell
      • Protons either bring in or expel other substances
    • Example: efflux pumps used in antimicrobial resistance
  • ATP Binding Cassette system (ABC transport)
    • Use binding proteins to scavenge and deliver molecules to transport complex
    • Example: maltose transport
cytoplasmic membrane11
Cytoplasmic Membrane
  • Group transport
    • Transport mechanism that chemically alters molecule during passage
      • Uptake of molecule does not alter concentration gradient
      • Phosphotransferase system example of group transport mechanism
        • Phosphorylates sugar molecule during transport
          • Phosphorylation changes molecule and therefore does not change sugar balance across the membrane
cell wall
Cell Wall
  • Bacterial cell wall
    • Rigid structure
    • Surrounds cytoplasmic membrane
    • Determines shape of bacteria
    • Holds cell together
    • Prevents cell from bursting
    • Unique chemical structure
      • Distinguishes Gram positive from Gram-negative
cell wall1
Cell Wall
  • Rigidity of cell wall is due to peptidoglycan (PTG)
    • Compound found only in bacteria
  • Basic structure of peptidoglycan
    • Alternating series of two subunits
      • N-acetylglucosamin (NAG)
      • N-acetylmuramic acid (NAM)
    • Joined subunits form glycan chain
      • Glycan chains held together by string of four amino acids
        • Tetrapeptide chain
cell wall2
Cell Wall
  • Gram positive cell wall
    • Relatively thick layer of PTG
      • As many as 30
        • Regardless of thickness, PTG is permeable to numerous substances
    • Teichoic acid component of PTG
      • Gives cell negative charge
gram negative bacterial cell wall
Gram Negative Bacterial Cell Wall

Note thin Peptidoglycan layer inside a Lipopolysaccharide layer

cell wall3
Cell Wall
  • Gram-negative cell wall
    • More complex than G+
    • Only contains thin layer of PTG
      • PTG sandwiched between outer membrane and cytoplasmic membrane
      • Region between outer membrane and cytoplasmic membrane is called periplasm
        • Most secreted proteins contained here
        • Proteins of ABC transport system located here
cell wall4
Cell Wall
  • Outer membrane
    • Constructed of lipid bilayer
      • Much like cytoplasmic membrane but outer leaflet made of lipopolysaccharides not phospholipids
      • Outer membrane also called the lipopolysaccharide layer or LPS layer
    • LPS severs as barrier to a large number of molecules
      • Small molecules or ions pass through channels called porins
    • Portions of LPS medically significant
      • O-specific polysaccharide side chain
      • Lipid A
cell wall5
Cell Wall
  • O-specific polysaccharide side chain
    • Directed away from membrane
      • Opposite location of Lipid A
    • Used to identify certain species or strains
      • E. coli O157:H7 refers to specific O-side chain
  • Lipid A
    • Portion that anchors LPS molecule in lipid bilayer
    • Plays role in recognition of infection
      • Molecule present with Gram negative infection of bloodstream
cell wall6
Cell Wall
  • Peptidoglyan (PTG) as a target
    • Many antimicrobial interfere with the synthesis of PTG
    • Examples include
      • Penicillin
      • Lysozyme
cell wall7
Cell Wall
  • Penicillin
    • Binds proteins involved in cell wall synthesis
      • Prevents cross-linking of glycan chains by tetrapeptides
    • More effective against Gram positive bacterium
      • Due to increased concentration of PTG
      • Penicillin derivatives produced to protect against Gram negatives
cell wall8
Cell Wall
  • Lysozymes
    • Produced in many body fluids including tears and saliva
    • Breaks bond linking NAG and NAM
      • Destroys structural integrity of cell wall
    • Enzyme often used in laboratory to remove PTG layer from bacteria
      • Produces protoplast in G+ bacteria
      • Produces spheroplast in G- bacteria
cell wall9
Cell Wall
  • Differences in cell wall account for differences in staining characteristics
    • Gram-positive bacterium retain crystal violet-iodine complex of Gram stain
    • Gram-negative bacterium lose crystal violet-iodine complex
cell wall10
Cell Wall
  • Some bacterium naturally lack cell wall
    • Mycoplasma
      • Bacterium causes mild pneumonia
      • Have no cell wall
        • Antimicrobial directed towards cell wall ineffective
      • Sterols in membrane account for strength of membrane
  • Bacteria in Domain Archaea
    • Have a wide variety of cell wall types
    • None contain peptidoglycan but rather pseudopeptidoglycan
layers external to cell wall
Layers External to Cell Wall
  • Capsules and Slime Layer
    • General function
      • Protection
        • Protects bacteria from host defenses
      • Attachment
        • Enables bacteria to adhere to specific surfaces
    • Capsule is a distinct gelatinous layer
    • Slime layer is irregular diffuse layer
    • Chemical composition of capsules and slime layers varies depending on bacterial species
      • Most are made of polysaccharide
        • Referred to as glycocalyx
          • Glyco = sugar calyx = shell
flagella and pili
Flagella and Pili
  • Some bacteria have protein appendages
    • Not essential for life
      • Aid in survival in certain environments
    • They include
      • Flagella
      • Pili
flagella and pili1
Flagella and Pili
  • Flagella
    • Long protein structure
    • Responsible for motility
      • Use propeller like movements to push bacteria
      • Can rotate more than 100,00 revolutions/minute
        • 82 mile/hour
    • Some important in bacterial pathogenesis
      • H. pylori penetration through mucous coat
flagella and pili2
Flagella and Pili
  • Flagella structure has three basic parts
    • Filament
      • Extends to exterior
      • Made of proteins called flagellin
    • Hook
      • Connects filament to cell
    • Basal body
      • Anchors flagellum into cell wall
flagella and pili3
Flagella and Pili
  • Bacteria use flagella for motility
    • Motile through sensing chemicals
      • Chemotaxis
    • If chemical compound is nutrient
      • Acts as attractant
    • If compound is toxic
      • Acts as repellent
  • Flagella rotation responsible for run and tumble movement of bacteria
flagella and pili4
Flagella and Pili
  • Pili
    • Considerably shorter and thinner than flagella
    • Similar in structure
      • Protein subunits
    • Function
      • Attachment
        • These pili called fimbre
      • Movement
      • Conjugation
        • Mechanism of DNA transfer
internal structures
Internal Structures
  • Bacterial cells have variety of internal structures
  • Some structures are essential for life
    • Chromosome
    • Ribosome
  • Others are optional and can confer selective advantage
    • Plasmid
    • Storage granules
    • Endospores
internal structures1
Internal Structures
  • Chromosome
    • Resides in cytoplasm
      • In nucleoid space
    • Typically single chromosome
    • Circular double-stranded molecule
    • Contains all genetic information
  • Plasmid
    • Circular DNA molecule
      • Generally 0.1% to 10% size of chromosome
    • Extrachromosomal
      • Independently replicating
    • Encode characteristic
      • Potentially enhances survival
        • Antimicrobial resistance
internal structure
Internal Structure
  • Ribosome
    • Involved in protein synthesis
    • Composed of large and small subunits
      • Units made of riboprotein and ribosomal RNA
    • Prokaryotic ribosomal subunits
      • Large = 30S
      • Small = 50S
      • Total = 70S
    • Larger than eukaryotic ribosomes
      • 40S, 60S, 80S
      • Difference often used as target for antimicrobials
internal structures2
Internal Structures
  • Storage granules
    • Accumulation of polymers
      • Synthesized from excess nutrient
        • Example = glycogen
          • Excess glucose in cell is stored in glycogen granules
  • Gas vesicles
    • Small protein compartments
      • Provides buoyancy to cell
      • Regulating vesicles allows organisms to reach ideal position in environment
internal structures3
Internal Structures
  • Endospores
    • Dormant cell types
      • Produced through sporulation
      • Theoretically remain dormant for 100 years
    • Resistant to damaging conditions
      • Heat, desiccation, chemicals and UV light
    • Vegetative cell produced through germination
      • Germination occurs after exposure to heat or chemicals
      • Germination not a source of reproduction

Common bacteria genus that produce endospores include Clostridium and Bacillus

internal structures4
Internal Structures
  • Endospore formation
    • Complex, ordered sequence
  • Bacteria sense starvation and begin sporulation
    • Growth stops
    • DNA duplicated
    • Cell splits
      • Cell splits unevenly
        • Larger component engulfs small component, produces forespore within mother cell
          • Forespore enclosed by two membranes
    • Forespore becomes core
    • PTG between membranes forms core wall and cortex
    • Mother cell proteins produce spore coat
    • Mother cell degrades and releases endospore
eukaryotic plasma membrane
Eukaryotic Plasma Membrane
  • Similar in chemical structure and function of cytoplasmic membrane of prokayote
    • Phospholipid bilayer embedded with proteins
  • Proteins in bilayer perform specific functions
    • Transport
    • Maintain cell integrity
      • Attachment of proteins to internal structures
    • Receptors for cell signaling
      • Proteins in outer layer
        • Receptors typically glycoproteins
  • Membrane contains sterols for strength
    • Animal cells contain cholesterol
    • Fungal cells contain ergosterol
      • Difference in sterols target for antifungal medications
eukaryotic plasma membrane1
Eukaryotic Plasma Membrane
  • Transport across eukaryotic membrane
    • Some molecules pass through membrane via transport proteins
    • Others taken in through endocytosis and exocytosis
eukaryotic plasma membrane2
Eukaryotic Plasma Membrane
  • Transport proteins
    • Function as carriers or channels
    • Channels create pores in membrane
      • Channels are gated
        • Open or closed depending on environmental conditions
          • Concentration gradient
    • Carriers analogous to prokaryotic membrane proteins
      • Mediate facilitated diffusion and active transport
eukaryotic plasma membrane3
Eukaryotic Plasma Membrane
  • Endocytosis
    • Process by which eukaryotic cells bring in material from surrounding environment
      • Pinocytosis most common type in animal cell
        • Pinch off small portions of own membrane along with attached material
          • Internalize vesicle and contents
        • Vesicle called endosome
eukaryotic plasma membrane4
Eukaryotic Plasma Membrane
  • Endocytosis
    • Phagocytosis
      • Specific type of endocytosis
      • Important in body defenses
      • Phagocyte sends out pseudopods to surround microbes
        • Phagocyte brings microbe into vacuole
          • Vacuole = phagosome
      • Phagosome fuses with a sack of enzymes and toxins
        • Sack = lysosome
        • Fusion of phagosome and lysosome creates phagolysosome
          • Microbe dies in phagolysosome
      • Phagosome breaks down microbial material
eukaryotic plasma membrane5
Eukaryotic Plasma Membrane
  • Exocytosis
    • Reverse of endocytosis
    • Vesicles inside cell fuse with plasma membrane
    • Releases contents into external environment
protein structures of eukaryotic cell
Protein Structures of Eukaryotic Cell
  • Eukaryotic cells have unique structures that distinguish them from prokaryotic
    • Cytoskeleton
    • Flagella
    • Cilia
    • 80s ribosome
protein structures of eukaryotic cell1
Protein Structures of Eukaryotic Cell
  • Cytoskeleton
    • Threadlike proteins
    • Reconstructs to adapt to cells changing needs
    • Composed of three elements
      • Microtubules
      • Actin filaments
      • Intermediate fibers
protein structures of eukaryotic cell2
Protein Structures of Eukaryotic Cell
  • Microtubules
    • Thickest of cytoskeleton structures
    • Long hollow cylinders
      • Protein subunits called tubulin
    • Form mitotic spindles
    • Main structures in cilia and flagella
protein structures of eukaryotic cell3
Protein Structures of Eukaryotic Cell
  • Actin filaments
    • Composed of actin polymer
    • Enable cell cytoplasm to move
      • Assembles and disassembles causing motion
        • Pseudopod formation
protein structures of eukaryotic cell4
Protein Structures of Eukaryotic Cell
  • Intermediate fibers
    • Function to strengthen cell
    • Enable cells to resist physical stress
protein structures of eukaryotic cell5
Protein Structures of Eukaryotic Cell
  • Flagella
    • Flexible structure
    • Function in motility
    • 9+2 arrangement
      • 9 pairs of microtubules surrounded by 2 individual
  • Cilia
    • Shorter than flagella
    • Often cover cell
    • Can move cell or propel surroundings along stationary cell
arrangements of bacterial flagella
Arrangements of Bacterial Flagella
  • Monotrichous: Bacteria with a single polar flagellum located at one end (pole)
  • Amphitrichous: Bacteria with two flagella, one at each end
  • Peritrichous: Bacteria with flagella all over the surface
  • Atrichous: Bacteria without flagella
  • Cocci shaped bacteria rarely have flagella
membrane bound organelles of eukaryotes
Membrane-bound Organellesof Eukaryotes
  • Eukaryotes have numerous organelles that set them apart from prokaryotic cells
    • Nucleus
    • Mitochondria and chloroplast
    • Endoplasmic reticulum
    • Golgi apparatus
    • Lysosome and peroxisomes
membrane bound organelles of eukaryotes1
Membrane-bound Organellesof Eukaryotes
  • Nucleus
    • Distinguishing feature of eukaryotic cell
    • Contains DNA
    • Area of DNA replication
      • Mitosis = asexual
      • Meiosis = sexual
  • Mitochondria
    • Site of energy production
    • Surrounded by membrane bilayer
      • Inner and outer membrane
        • Outer membrane invaginations called cristae
        • Matrix formed from inner membrane
          • Contains DNA
membrane bound organelles of eukaryotes2
Membrane-bound Organellesof Eukaryotes
  • Chloroplast
    • Found only in plant and algae
    • Site of photosynthesis
    • Surrounded by two membranes
  • Endoplasmic reticulum
    • Divided into rough and smooth
      • Rough ER
        • embedded with ribosomes
        • Site of protein synthesis
      • Smooth ER
        • Lipid synthesis and degradation
        • Calcium storage
membrane bound organelles of eukaryotes3
Membrane-bound Organellesof Eukaryotes
  • Golgi apparatus
    • Consists of a series of membrane bound flattened sacs
    • Modifies macromolecules produced in endoplasmic reticulum
  • Lysosomes & Peroxisomes
    • Lysosomes contain degradative enzymes
      • Proteases and nucleases
    • Peroxisomes
      • Organelles in which oxygen is used to oxidize substances
        • Breaking down lipids
        • detoxification
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