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Microbiology > Ch.3 Microscopy and Cell Structure > Flashcards

Ch.3 Microscopy and Cell Structure Flashcards

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1
Q

Eukaryotic

A
  • multicellular
  • nucleus
  • more complex than prokaryotes
  • larger
  • many cellular processes take place within membrane-bound compartments
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2
Q

Examples of Eukaryotes

A
  • Animals
  • Plants
  • Protozoa
  • Fungi
  • Algae
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3
Q

Prokaryotic

A
  • unicellular
  • no nucleus, has nucleoid region
  • small size gives prokaryotes:
    – high surface area (skin) to volume (liquid inside) ratio making it easier for them to take in nutrients and excrete waste
    – makes cell vulnerable to threats like redators, prasites and competitors
  • has unique fetaures that increase chances of survival
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4
Q

Examples of Prokaryotes

A
  • Bacteria = peptidoglycan in cell wall
  • Archaea = no peptidoglycan
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5
Q

Prokaryote Cell Structures

A
  • cytoplasm
  • nucleoid = location of chromsome
  • locator appendages
    Surface layers:
  • Capsule (on top)
  • cell wall: made up of petidoglycan
  • cytoplasmic membrane
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6
Q

Review Question

Cytoplasmic membrane

A

phospholoipd bilayer embedded w/ proteins
- hydrophobic tails face inward
- hydrophilic heads face outward
- proteins serve as selective gates, sensors of environemntal conditions, enzymes
- Fluid mosaic model: proteins drift in lipid bilayer

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7
Q

Review

Cytoplasmic membrane

Prokaryotes

A
  • Bacteria and Archaea have same general structure of cytoplasmic membranes
  • both have distinctly different phospholipid compositions
    – lipid tails of Archea are not fatty acids
    – connected differently to glycerol
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8
Q

Review Question

Permeability of Cytoplasmic Membrane

A
  • selectively permeable
  • Passes through easily: gases (O2, CO2, N2), small hydrophobic molecules, water
  • do not pass through: sugars, ions, amino acids, ATP, macromolecules
  • some cells can facilitate water passage with aquaporins
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9
Q

Simple Diffusion

A
  • passive
  • w/o help of transport proteins
  • high to low concentration
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10
Q

Facilitated diffusion

A
  • passive
  • w/ help of transport proteins
  • high to low concentration (down concentration gradient)
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11
Q

Review Question

Speed of diffusion

across cytoplasmic membrane

A

depends on concentration
- the greater the difference in concentration on either side of a membrane, the high rate of diffusion

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12
Q

Solution

A

Solute + Solvent

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13
Q

Solute

A

substance dissolved

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14
Q

Solvent

A

Substance doing the dissolving
Ex: water

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15
Q

osmosis

A

diffusion of solvent across a selectively permeable membrane due to unequal solute concentrations
- water diffuses from high to low water concentration

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16
Q

Isotonic Solution

Osmosis

A
  • no net water flow
  • solute = solvent
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17
Q

Hypertonic Solution

Osmosis

A
  • Solute is high in solution
  • water flows out of cell
  • Cell shrinks
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18
Q

Hypotonic Solution

A
  • solute low in solution
  • water flows into cell
  • cell swells
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19
Q

Environment of prokaryotes

A

dilute hypotonic relative to cytoplasm
- cell wall prevents cell from bursting

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20
Q

Review Question

Electron Transport Chain (ETC)

A
  • embedded in cytoplasmic membrane
  • uses energy from electrons to move protons out of cell
  • creates electrochemical gradient across membrane
  • energy called proton motive force
  • harvested to drive ATP synthesis and some forms of transport, motility
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21
Q

Review Question

Transport systems in cytoplasmic membrane

A
  • moves nutreients and other small molecules across the cytoplasmic membrane
  • Ex: transporters, permeases or carriers
  • membrane-spanning
  • highly specific: a single transporter generally moves only one molecule type
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22
Q

Efflux pumps

A
  • transporters that move waste products and other toxic susbstances out of cells
  • important medically because bacterial cells use them to remove antimicrobial medications that have entered
  • Allow the bacterium to withstand the effects of the medication.
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23
Q

active transport

A
  • Requires energy
  • Moves low to high (against concentration gradient)
  • driven by proton motive force or by ATP (ABC transporter)
  • Ex: efflux pump
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24
Q

Review Question

Group Translocation

A
  • Common in bacteria to bring glucose into the cell
  • Chemically alters compound during passage through cytoplasmic membrane
  • Phosphorylation common
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25
Q

Protein Secretion

A
  • Active movement of proteins out of cell
  • Ex: exoenzymes (extracellular enzymes), external structures
  • Polypeptides tagged for secretion via signal sequence of amino acids
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26
Q

Cell Wall of Prokaryotic Cells

A
  • strong
  • rigid structure that prevents cell from bursting
  • Gram-positive
  • Gram-negative
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27
Q

Review Question

Gram-positive

Cell Wall of Bacteria

A
  • purple
  • thick peptidoglycan
  • located on the outer membrane
  • Teichoic acids extend above peptidoglycan layer
  • Gel-like material called periplasm between cell membrane and peptigylican layer
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28
Q

Review question

Gram negative

Cell Wall of Bacteria

A
  • pink
  • thin peptidoglycan in periplasmic space which is located between cytoplasmic membrane and outer membrane
  • 2 phospholipid layers
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29
Q

gram negative –> periplasmic space

A
  • Filled with gel-like periplasm
  • Exported proteins accumulate unless specifically moved across outer membrane
  • Binding proteins of ABC transport systems
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30
Q

gram negative –> Outer phospholipid membrane

A
  • contains lipopolysaccharide (LPS):
    – LPS signals immune system of invasion by Gram-negative bacteria
    — Small levels elicit response to eliminate invader
    – LPS is an endotoxin and large amounts accumulating in bloodstream can be deadly
  • Includes Lipid A and O antigen
  • blocks passage of many molecules including certain antimicrobial medications
    – Small molecules and ions can cross via porins
    – Secretion systems important in pathogenesis
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31
Q

Peptidoglycan

A
  • Alternating series of subunits form glycan chains
    – N-acetylmuramic acid (NAM)
    – N-acetylglucosamine (NAG)
  • Tetrapeptide chain attach to the NAM and link glycan chains together
    – Direct link in Gram-negative cells
    – Peptide interbridge in Gram-positive cells
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32
Q

Review Question

Antibacterial Substances That Target Peptidoglycan

A
  • Interference with peptidoglycan can weaken cell wall and allow cell to burst
  • Penicillin interferes with peptidoglycan synthesis
    – Prevents cross-linking of adjacent glycan chains
    – Outer membrane of Gram-negative cells blocks access
    – Derivatives have been developed that can cross
  • Lysozyme breaks bonds linking glycan chains
    – Enzyme found in tears, saliva, other body fluids
    – Destroys structural integrity of peptidoglycan
  • *Both more effective against Gram-positive bacteria than gram-negative bacteria
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33
Q

Bacteria That Lack Cell Wall

A

Ex: Mycoplasma species are flexible because they lack a rigid cell wall
- Mycoplasma can survive without a cell wall because their cytoplasmic membrane contains sterols

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34
Q

Cell Walls of Archaea

A
  • No peptidoglycan, but some have similar molecule pseudopeptidoglycan
  • variety of cell walls due to range of environment
  • have S-layers are built from sheets of flat protein or glycoprotein subunits and self-assemble
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35
Q

Capsules and Slime Layers

A
  • Gel-like layer outside cell wall protects or allows attachment
  • Capsule: distinct, gelatinous
  • Slime layer: diffuse, irregular
  • composed of glycocalyx (sugar shell) or polypeptides
  • Once attached to a surface, cells can grow as biofilm
  • Example: dental plaque
  • Some capsules allow bacteria to evade host immune system
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36
Q

Flagella

A

Three parts of bacterial flagellum:
- Basal body: anchors to cell wall and cytoplasmic membrane
- Hook
- Filament: made up of flagellin subunits
- involved in motility by spinning like propellers
- Some important in disease –> Ex: Helicobacter pylori
- Peritrichous: flagella distributed around surface of the cell
- Polar: a single flagellum at one end

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37
Q

Archaella (flagella of Archae)

A
  • Chemically distinct from those of Bacteria
  • About half the diameter of bacterial flagella
  • Use energy from ATP instead of proton motive force
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38
Q

Chemotaxis

A
  • Bacteria sense a chemical and move toward it (nutrient) or away from it (toxin)
  • Movement is series of runs (straight line) and tumbles (changes in direction) due to coordinated rotation of flagella
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39
Q

types of chemotaxis

A
  • Aerotaxis: respond to O2
  • Magnetotaxis: respond to earth’s magnetic field
  • Thermotaxis: respond to temperature
  • Phototaxis: respond to light
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40
Q

Pili

A
  • shorter and thinner than flagella and the function is different
  • Common pili, or fimbriae, allow the bacterial cells to attach to specific surfaces
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41
Q

Sex pili

A

used to join one bacterium to another for DNA transfer

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42
Q

nucleoid

prokaryotic

A
  • Chromosome forms gel-like region
  • Single circular double-stranded DNA molecule
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43
Q

Plasmids

prokaryotic

A
  • Do not encode essential genetic information
  • May be shared with other bacteria; antibiotic resistance can spread this way
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44
Q

Ribosomes

prokaryotic

A
  • smaller
  • involved in protein sythesis
  • Facilitate joining of amino acids
  • Relative size and density expressed as S (Svedberg unit) that reflects how fast they settle when centrifuged
  • Prokaryotic ribosomes are 70S
  • Composed of 30S and 50S subunits
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45
Q

Eukaryotic ribosomes

A
  • are 80S made up of 60S and 40S subunits
  • antibiotics do not affect 80S ribosome
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46
Q

Prokaryotic ribosomes

A

are 70s

47
Q

Review Question

cytoskeleton

prokaryotic

A
  • Bacterial proteins similar to eukaryotic cytoskeleton have been characterized
  • Likely involved in cell division and controlling cell shape
48
Q

Storage granules

A
  • accumulations of polymers
  • Synthesized from nutrients available in excess
    – Carbon, energy storage:
    — Glycogen
    — Poly-β-hydroxybutyrate (PHB)
    – Metachromatic granules stain red with methylene blue
    – Protein-based compartments: separate reactions or functions
  • Small rigid structures
  • Identical protein subunits forming the semi-permeable container
49
Q

Gas vesicles

A
  • provide aquatic prokaryotes with a mechanism of adjustable buoyancy to move up and down
  • Allow only gases to flow in freely, thereby decreasing the density of the cell
50
Q

Bacterial microcompartments (BMCs)

A
  • contain enzymes required for certain metabolic reactions
  • By confining these in a compartment, the cell prevents unwanted side reactions and protects the cytosol from toxic metabolites.
51
Q

Encapsulin nanocompartments

A
  • the most recently discovered type of compartment.
  • hold certain proteins in isolation
52
Q

Review Question

Endospores

A
  • remain dormant for 100 years or longer
  • Extremely resistant to heat, desiccation, chemicals, ultraviolet light, boiling water
  • Can germinate to become vegetative cells (actively growing)
  • Sporulation triggered by limited carbon or nitrogen
  • Germination triggered by heat, chemical exposure
  • Not a means of reproduction
53
Q

Protozoa

A

self-contained units with no cell wall

54
Q

Animal cells

A

lack a cell wall

55
Q

Fungal cells

A

have a cell wall containing polysaccharides such as chitin

56
Q

Plant cells

A

have a cell wall composed of cellulose

57
Q

organelles

A
  • Membrane-enclosed compartments in eukaryotes
  • Ex: Nucleus contains cell’s DNA
58
Q

membrane bound vesicles

eukaryotic

A

bud off from one organelle and fuse with another, delivering material to lumen of organelle

59
Q

Cytoplasmic Membrane of Eukaryotic Cells

A
  • Phospholipid bilayer embedded with proteins
  • Proteins in outer layer serve as receptors
  • Bind specific molecule called a ligand: Important in cell communication
  • contain sterols to increase strength
  • Examples: Cholesterol in mammals, ergosterol in fungi
  • Lipid rafts: allow cell to detect, respond to signals
  • Electrochemical gradient maintained by sodium or proton pumps
60
Q

Aquaporins

eukaryotic

A

water passage

61
Q

Channels

eukaryotic

A

small gated pores, allow small molecules or ions to diffuse

62
Q

Carriers

eukaryotic

A

facilitated diffusion, active transport

63
Q

Review Question

Endocytosis

A

cell takes up material from surrounding environment by forming invaginations in cytoplasmic membrane

64
Q

Exocytosis

A

internal vesicles fuse with the cytoplasmic membrane and release their contents

65
Q

Review Question

Pinocytosis

type of endocytosis

A
  • most common in animal cells (Eukarya domain)
  • Forms endosome, which fuses to lysosomes
  • Material degraded in endolysosome
66
Q

Review Question

Receptor-mediated endocytosis

type of endocytosis

A

allows cell to take up specific extracellular ligands that bind to surface receptors
- takes place in Eukarya domain

67
Q

Review Question

Phagocytosis

type of endocytosis

A
  • cells engulf particulate material such as bacteria
  • used by Protozoa domain, phagocytes to engulf
  • Pseudopods surround, bring material into phagosome
  • Phagosome fuses with lysosome to form phagolysosome where material is degraded
68
Q

Secretion

A
  • Proteins destined for secretion carry a signal sequence that acts as a tag
  • Ribosomes synthesizing protein with a signal sequence attach to endoplasmic reticulum (ER)
  • Protein enters lumen of ER
  • Membrane of ER buds off and binds to cytoplasmic membrane, releasing protein outside the cell
  • Proteins going to other organelles have specific tags
69
Q

Review Question

cytoskeleton

eukaryotic

A
  • cell framework
    1. actin filaments
    2. microtubles
    3. intermediate filaments
70
Q

Review Question

actin filaments

part of cytoskeleton in eukaryotic

A
  • allow movement
  • polymers of actin polymerize and depolymerize
71
Q

Review Question

Microtubles

part of cytoskeleton in eukaryotic

A
  • are thickest component
  • Long, hollow structures made of tubulin
  • Found in mitotic spindles, cilia, flagella
  • Framework for organelle and vesicle movement
72
Q

Review Question

Intermediate filaments

part of cytoskeleton in eukaryotic

A
  • provide mechanical support
73
Q

Pathogens

A

control polymerization and depolymerization of host cell’s actin

74
Q

flagella and cillia

eukaryotic

A
  • function in motility –> propel cell or pull it forward
  • Covered by extensions of cytoplasmic membrane
  • Composed of microtubules in 9 + 2 arrangement
  • Cilia are shorter than flagella, move synchronously
    – Can move cell forward or move material past stationary cells
75
Q

Review Question

nucleus

eukaryotic

A
  • contains the genetic information
  • Surrounded by two phospholipid bilayer membranes
  • Nuclear pores allow large molecules to pass
  • Nucleolus is region where ribosomal RNAs synthesized
76
Q

mitochondria

eukaryotic

A
  • Generate ATP
  • Bounded by two phospholipid bilayers
  • Inner membrane forms folds (cristae), increasing surface area for ATP generation
  • Mitochondrial matrix contains DNA, 70S ribosomes
77
Q

Review Question

Endosymbiosis Theory

A

Ancestors of mitochondria and chloroplasts were bacteria residing within other cells

78
Q

Review Question

Evidence of Endosymbiotic Theory

A
  1. Carry DNA for some ribosomal proteins, ribosomal RNA
  2. Ribosomes similar to bacterial 70s ribosomes
  3. Multiplication is by binary fission
  4. Mitochondrial DNA sequences resemble those of obligate intracellular parasites: rickettsias
  5. Chloroplast DNA sequences resemble those of cyanobacteria
79
Q

Chloroplasts

A
  • Sites of photosynthesis
  • Found only in plants, algae
  • Harvest sunlight energy to generate ATP
    –> CO2 to sugar and starch
  • Contain DNA and 70S ribosomes, two membranes
  • Stroma contains thylakoids containing pigments that capture radiant energy
80
Q

Endoplasmic Reticulum (ER)

A
  • System of flattened sheets, sacs, tubes
81
Q

Rough endoplasmic reticulum

A
  • dotted with ribosomes
  • Synthesize proteins not destined for cytoplasm
82
Q

Smooth endoplasmic reticulum

A

lipid synthesis and degradation, calcium storage

83
Q

Golgi Apparatus

A
  • Membrane-bound flattened compartments
  • Macromolecules synthesized in ER are modified
  • Molecules sorted and delivered in vesicles
84
Q

Lysosomes

A
  • contain degradative enzymes
  • Could destroy cell if not contained
  • Endosomes, phagosomes fuse with lysosomes
    – Material taken up by cell is degraded
    – Old organelles, vesicles fuse with lysosomes: autophagy
85
Q

Peroxisomes

A
  • use O2 to degrade lipids, detoxify chemicals
  • Peroxisome generates, contains, and ultimately degrades hydrogen peroxide, superoxide
86
Q

Light microscope

A

can magnify 1,000x

87
Q

electron micrscope

A

can magnify more than 100,000x

88
Q

Scanning probe microscope

A

can produce images of individual atoms on a surface

89
Q

Review Question: resolving power

Principles of Light Microscopy

A
  • Light passes through specimen
  • Most common type is Bright-field microscope
    Three key concepts:
  • Magnification: increase in size
  • Resolution: resolving power or ability to distinguish two objects that are very close together
    – Depends on quality and type of lens, wavelength of light, magnification, and specimen preparation
    – Maximum resolving power of light microscope is 0.2 micrometer
  • Contrast: difference in color intensity between an object and the background
90
Q

What are the two types of lenses found in a light microscope?

A

objective and ocular lens

91
Q

Modern compound microscope (6 parts)

A
  1. ocular lens: magnifies image by 10x
  2. objective lens: set of lens options that provodes sifferent magnifications
  3. condenser lens: focuses the light
  4. iris diaphram lever: controls amount of light that enters the objective lens
  5. Rheostat: controls the brightness of the light
  6. light source
92
Q

Immersion oil

A
  • used to displace air between lens and specimen when using high powered 100x objective
  • Prevents refraction of light
93
Q

What organism lacks contrast?

A

transparent bacteria

94
Q

Dark Field microscope

A

Cells appear as bright objects against dark background

95
Q

Phase-Contrast Microscope

A

Makes cells and other dense material appear darker

96
Q

Differential Interference Contrast (DIC) Microscope

A
  • Separates light into two beams that pass through specimen and recombine
  • Light waves are out of phase when recombined, yield three- dimensional appearance of image
97
Q

Fluorescence Microscope

A

Used to observe cells or materials either naturally fluorescent or tagged with fluorescent dyes

98
Q

Scanner Laser Microscopes

A

Allows detailed interior views of intact cells

99
Q

Confocal Microscopy

A

Like a miniature computerized axial tomography (CAT) scan for cells

100
Q

Electron Mcroscopes

A
  • Resolving power approximately 1,000-fold greater: approximately 0.3 nanometer
    Two major types:
  • Transmission Electron Microscope (TEM)
  • Scanning Electron Microscope (SEM)
101
Q

Scanning Electron Microscope (SEM)

Electron Microscope type

A
  • beam of electrons scans over surface of specimen
  • yields 3-D effect
102
Q

Transmission Electron Microscope (TEM)

Electron Microscope type

A

beam of electrons passes through specimen or scatters

103
Q

Preparing Specimens for Light Microscopy

A
  • Wet mount uses a drop of liquid specimen overlaid with a coverslip
  • Smear involves drying and fixing specimen before staining to visualize
104
Q

Simple staining: Basic dyes

A

Basic dyes carry positive charge
- Attracted to negatively charged cellular components

105
Q

Simple staining: acidic dyes

A

can be used for negative staining
- Cells repel the negatively charged dye; colorless cells stand out

106
Q

Review question

Differential stain

A

used to distinguish different groups of bacteria

107
Q

Review Question

Gram stain orfer

A

widely used for bacteria
1. Flood smear with primary stain
2. Rinse and flood with iodine, a mordant that stabilizes the dye
3. Rinse and add alcohol, a decolorizing agent, to remove dye complex from Gram-negative cells to turn colorless
4. Rinse and flood smear with counterstain that turns Gram-negative cells pink

108
Q

Acid-Fast Stain

A
  • used to detect organisms that do not readily take up dyes
  • detects Mycobacterium
  • Cell wall contains high concentrations of mycolic acids
109
Q

Capsule stain

A
  • Capsules stain poorly, so background is stained to make capsule visible
  • Solution: India ink added
110
Q

Endospore Stain

A
  • endospores formed by Bacillus and Clostridium
  • Endospore stain uses heat to facilitate uptake of the primary dye malachite green by endospore
111
Q

Flagella Stains

A

uses substance that adheres to thin flagella, making them visible

112
Q

Fluorescent Dyes

A

Immunofluorescence uses fluorescent dye-antibody labels to tag a unique microbe protein

113
Q

Review Question

Why can a stain stick to the plasma membrane of a cell? What charge is the dye and what charge is the plasma membrane?

A
  • A stain typically sticks to a cell’s plasma membrane because most stains are positively charged (“basic dyes”)
  • the plasma membrane has a negative charge, causing an electrostatic attraction between the two
114
Q

Review Question

What are the 2 locations ASIDE from the nucleus in Eukaryotes and Nucleoid Region in prokaryotes where extrachromosomal DNA can be found?

A
  1. mitochondrial matrix inside mitochondria
  2. chloroplasts

Microbiology (9 decks)

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